Post by: vtsteam on February 22, 2025, 02:39:40 PM
Eighteen years ago for my father's 83rd birthday, I built a hot air engine using my own aluminum castings, skate ball bearings, a graphite piston, and many borrowings from my scrap pile. It was a very rushed 2 week project, since I had little idea of the complexities I was getting myself into. I worked long into the nights. Nevertheless I finished the little engine the night before leaving to see him, and got the bare engine to run, rather impressively, by heating the displacer cylinder over the kitchen stove. I quickly added a channel Iron base, a firebox out of square tube, and a smokestack out of a brass sink drainpipe. The firebox even had a door.
When visiting him a few states away, I brought a small can of Sterno as a heat source, and this fit into the firebox, and luckily was enough to power the engine as well, running steadily. All was well!
Because we had to return home the next day, I took some pictures of the engine on a rather fancy table. The engine was named "No. 83" in honor of my father's birthday. Those photos were all I had of the engine for many years, and I really regretted I didn't have more time to run it, improve it, and try out the many ideas I had as experiments. In fact the original intention was to run it with wood as a fuel, and the firebox and stack were built with that in mind. But that never happened.
Not to go into too many personal details but my father later had a bad fall, was hospitalized and sedated for a week, lapsed into partial dementia, and my brother, an heroin addict and ex-con, took over his life. My father passed away, and my brother took everything, including the little engine. That was the end of it, so I thought.
My nephew, a kind person, recently returned the engine to me after his father, my brother, had also passed. It had been 18 years. My brother had pronounced my engine non-workable after trying and failing to run it once for my father. He had no concept of what a hot air engine really is or how it works. After my father died, my brother had left No. 83 in the corner of a garage on the bare concrete to rust.
The .008" walled displacer cylinder had been overheated and ruptured. The fire door was missing. No. 83 was in sad shape.
Post by: vtsteam on February 22, 2025, 03:43:55 PM
Post by: tom osselton on February 22, 2025, 03:49:40 PM
Post by: vtsteam on February 24, 2025, 04:00:30 PM
I haven't, a lot my stuff is under tons of snow here which came off the open sided casting shed roof on top of the two feet we already had. A lot of it had drifted underneath. I just shoveled a lot of it out today. Hoping to cast something when this last bunch of ice and snow clears up more.
re. No 83: Well as a start, I cleaned the outer engine with mostly just soap and hot water and a 3M Scotchbrite pad. That felt a lot better!
Then I took apart the linkages, cleaned them and put them back together. No telling whether it will run again without replacing some of those parts. But for the moment I think I'll try with what I have.
Post by: vtsteam on February 24, 2025, 04:19:27 PM
This is quite a bit thicker walled than the old one was. It's .047" while the older cylinder had a wall thickness of only .008" at the hot end! (The cold end was full thickness, also ~.047", so the mount in the massive bulkhead/heat sink will be the same).
Turning the hot end down that thin was very tedious. Eighteen years ago I had turned it between centers using tiny cuts. The cylinder had been jam-mounted onto a carefully turned oak dowel arbor, to give it support.
I'm anxious to see if the engine works, so I'm just going to try it as-is. I can always turn it down in thickness in future. I hope it will at least run okay without the thinning, just not at maximum efficiency. Or maybe it won't run at all, for this or other reasons. We'll see.....
Post by: vtsteam on February 24, 2025, 05:03:23 PM
Design note: I had originally hoped to mount the cylinder as a press fit into that bulkhead, but had bored it .002" oversize by mistake. I had wanted good heat transfer into the aluminum as a cooler hence the press fit. The remedy, since time was so short on this original birthday present project, was to immobilize the cylinder with the allen screws, after applying electronic heat sink compound to the bore to allow good heat transfer.)
Anyway, what to do about the stuck screw deep in the bulkhead? Well since the old cyinder was defunct anyway, I was able to pull it out, with some scratches -- but it was destined for the bin anyway. Luckily with the cylinder out, I was finally able to remove the stuck screw. Phew! :med:
But when I tried to slide the new cylinder in place, It wouldn't go. What the heck? They were the same exact OD.
After taking a careful look at the bore, I notice what looked like the tip of the same grub screw I had removed, still in place. Another one? Well yes, mystery solved! :smart:
I unscrewed that one, and could finally slide the new cylinder in place. Two screws had been put into the same hole. That explained the missing one from the other location 90 degrees away. Somebody had had the engine apart and then, uhhhhh... screwed it up. That would also have slightly changed the cylinder location from when originally tested. And possibly the angular alignment. It would also have allowed a little play, which is why two 90 degrees apart were originally intended. And jamming two on top of each other can make the top one hard to extract.
Okay, click, I'm starting to get a picture of events.....
Post by: vtsteam on February 25, 2025, 12:11:24 PM
Time to try to get the engine going. I left it to heat for a minute or so and gave then gave flywheel a flip. It didn't spin on its own, maybe four grudging turns to stop no matter how hard I tried.
Encouragingly, flipping the flywheel backwards had much higher resistance and went to an immediate stop, which to me meant at least I had a hot air engine. Flipping backwards turns a Stirling into a heat pump, and that actually takes work, rather than producing it. The difference is a sign that there is potential.
I then tried a Mapp torch -- but being careful not to to melt the end cap silver braze (which is hard - 70% silver). The engine turned over when flipped and I'd say it "ran" but really haltingly. I had to keep waving the torch on it as it tried to stop. It's not the way I remember it, and I don't want to damage it by continuing. At least I could see it go on its own, so it is a hot air engine. Of sorts.
What's wrong?
I know it was a better runner than that. It's time to take the whole engine apart and measure everything. Is there wear? Is there corrosion? Something is definitely wrong.
Post by: vtsteam on February 25, 2025, 12:42:12 PM
That's also an issue. This engine should be free spinning other than the compression resistance. It has twin ball bearing races on the crankshaft, and they are ABEC 7 rated skate bearings. The displacer is not contacting the walls of the displacer cylinder, and its polished pushrod is riding in a brass guide bushing that is still a close fit.
It's true that the crank linkages simply use 0.125" steel pins riding directly in holes in the aluminum connecting rods. But again the fit is still good, and their friction is tiny, and it's the same setup I had when it first ran 18 years ago. It's not enough to stop an engine.
Where I'm feeling a lot of friction is in the power piston and cylinder. Now this shouldn't be. That piston is graphite, and I remember lapping the brass cylinder it rides in with a lead lap and fine abrasive for probably an hour, trying to get a perfect fit. Why is it riding so badly now. And where is the compression?
The cylinder and piston both look good.... are they that far off now?
Post by: vtsteam on February 25, 2025, 01:24:28 PM
The flywheel spins VERY freely for more than a minute by itself. The displacer slides easily in its bushing. But the graphite piston and cylinder do not.
(Later):
Somebody oiled the piston! :wack: It's not meant to be oiled. That completely defeats the purpose of a graphite piston!
I was wondering what kind of oil they used. Maybe even kitchen vegetable oil, heaven forbid.... so I smelled the piston. It must have been "3-in-1" oil -- I remember that smell so well from when I was a kid and we were working on our bikes. Well I still have an old bottle of it. So distinctive.
I guess the friction problem was 18 year old oil sludge absorbed into the graphite of the piston. So I just washed the piston with dish detergent in hot water. And the brass cylinder as well. And now they are VERY free running together. Plus, the compression is back.
I can locate the piston and the little aluminum connecting rod in the cylinder held vertical and they fall right through under their own weight -- which is tiny. But if I put my thumb over the end, the piston stays suspended indefinitely because of compression, until I remove my thumb.
That's a big relief. I thought I might have to make a new piston.
Post by: tom osselton on February 25, 2025, 02:59:48 PM
Post by: vtsteam on February 25, 2025, 03:29:43 PM
Post by: vtsteam on February 26, 2025, 11:02:51 AM
And quite strongly, too. I've got to find my tachometer and see what it's doing.
Post by: awemawson on February 26, 2025, 01:42:09 PM
Post by: vtsteam on February 26, 2025, 02:47:39 PM
Post by: vtsteam on February 26, 2025, 02:58:00 PM
So, 800 RPM on No. 83, which is gratifying to see. It 's an impressive running engine. That flywheel is pretty massive, and it's fun watching it slowly come up to speed and then maintain that rate. It does seem to take nearly 5 minutes of heating (using sterno) before it will start, which seems kind of long. I'm not sure why it shouldn't start sooner. Maybe the thicker wall of the new displacer cylinder. I think I'll make another one.
Well anyway, she's running well now and I'm happy! All these years I wondered about it :scratch:
I keep running it, then stopping for an hour or two, then starting it up again just to see it go. It's just fun!
Top RPM is very consistent at about 800 each time.
Post by: Brass_Machine on February 26, 2025, 03:34:14 PM
Post by: vtsteam on February 26, 2025, 07:27:55 PM
Post by: vtsteam on February 26, 2025, 08:23:17 PM
Well, it wasn't a bug after all. It was the sensation of suction and compression 13 times a second coming from a tiny grub screw hole in the side of the bulkhead that my thumb was gripping. In other words, it was a leak!
Oh, man, of course the makeshift of fastening the displacer cylinder with those screws hadn't solved the problem of the (2 thou) oversized hole the cylinder was sitting in! Dumb! :bang: Pressure was escaping around that cylinder, and then out the grub screw hole.
And yet the engine has been running. It's amazing that the power pulses from just heating and cooling air 800 times a minute in a 1" diameter cylinder is so great that it can get around a 1 thou mounting gap, then around the screw threads of a bottomed out grub screw, and yet make itself felt that strongly. Hot air engines are continually surpising. I mean it's amazing they can run as fast as they do based on what's happening internally.
Okay well what to do about the leak? Hmmmm. Well wait a minute, there was a paper "head" gasket (tail gasket?) which should have sealed the rim of the cylinder, anyway, right? So where is it coming from?
Post by: Brass_Machine on February 27, 2025, 10:27:38 AM
Thanks Eric! :beer: How has the winter been treating you this year? Nasty here!
Has been insane.
Post by: vtsteam on February 27, 2025, 12:16:24 PM
Well, back to the matter at hand -- which keeps us from going cabin crazy :lol: um, oh yeah the leak....
It was the gasket. I made a new one out of brown paper grocery bag material (yes, I still have a few, just for that purpose). Reassembling the engine, No 83 is now consistently doing 1200 RPM, an improvement of 400 RPM. It's a lot more impressive. Like starting to seem a little scary, since it's unbalanced.
Kind of curious how far I can take this engine. I can think of a few things I'd like to test out. And since the components are easy to swap out (ie. NOT pressed fitted) and it's a reasonable scale (~1 bore power and displacer) it's simple to make alterations. Doesn't take a lot of material.
I had intended (for a couple years now) to make a much larger experimental hot air engine -- I have stainless tubing in both 2-1/2" and 4" dia. sizes, and a lot of other stuff specifically purchased for that.
But I'm thinking changes on that scale are more difficult and expensive to make. I can experiment with configurations on this little one much more easily, and then apply that to the design of the larger one.
So No. 83 might have an interesting future as a test bed. We're not done yet......
Post by: vtsteam on February 27, 2025, 05:44:26 PM
The older recent cylinder is shown next to it.
Post by: vtsteam on February 27, 2025, 07:23:17 PM
Linkages a blur.
Post by: vtsteam on February 28, 2025, 09:01:53 PM
To do all this I need to make a plug sleeve out of aluminum, and press that into the bulkhead. Here's the start:
Post by: vtsteam on February 28, 2025, 09:05:44 PM
Post by: vtsteam on February 28, 2025, 09:09:17 PM
Post by: vtsteam on February 28, 2025, 09:26:38 PM
I then started a third cylinder and press fitted it into an aluminum flange (which will provide additional cooling sink). The flange was drilled for four fixing screws. It's shown here fastened to the newly sleeved and bored bulkhead. The previous two cylinders are sitting next to it for comparison.
The new one will be shortened so that the overall length including the bulkhead is the same as the other two. I haven't capped it yet-- I've left it open to be able to see how the displacer is riding in the bore.
I'm happy with today's work and the new cylinder mount. :ddb:
Post by: vtsteam on March 02, 2025, 03:17:52 PM
Post by: vtsteam on March 02, 2025, 03:54:02 PM
The wear is in the brass guide, not the rod. Guides on a horizontal displacer hot air engine receive a lot more wear than a vertical.
Another detriment due to wear here is pressure leak. There's no seal other than a good fit over its 3/4" length. As built, the guide was permanently brazed in place. I've decided to make it replaceable by drilling and threading the existing guide 1/4 -28 to take a screw-in bushing.
I've got some sintered bronze material in the scrap box, and I think I'll make a guide bushing out of that. That material should reduce wear and friction compared to brass, and obviate the need for oiling.
Here's the guide, now opened up and threaded:
Post by: tom osselton on March 02, 2025, 05:04:16 PM
Post by: vtsteam on March 03, 2025, 11:22:30 PM
I spent time in the shop today adding a motorized spindle to a milling attachment I had once built for my old Gingery lathe. I found that the milling attachment does mount onto my newer homemade lathe with T-nuts in the boring table.
That was a fun, overdue project -- I've had the spindle for a year. The milling attachment was built in 2002. Neither had seen service on my present lathe until now.
I had planned to use this new rig to mill down the top of No 83's valve guide socket, since the new threaded bushing will have a head that would otherwise increase it's height. Seemed like a good reason to make up the tooling.
Got the rig working and set up, but :wack: I found I didn't have a 1/4" end mill to fit the spindle. All my 1/4" end mills have a 3/8" shank. The new spindle has an ER11 collet system which only handles up to a little more than 1/4". I thought about mounting a 1/8" end mill, but the one I had turned out to be too short to clear the power piston cylinder.
So in the end I went with the old fashioned way: I chucked an oversized drill bit in the drill press, and drilled out most of the way down on the valve guide, then finished up with a file to square the top off.
Oh well, glad to have the new powered milling attachment made up. I've ordered some 1/4" end mills with 1/4" shanks.
Post by: vtsteam on March 04, 2025, 07:30:53 PM
The attachment can be mounted crosswise as well. It's held down to the lathe's boring table with tee-nuts.
In today's work on No.83, I found I'd tapped the displacer rod guide off-vertical :wack:. So I mounted the whole power cylinder/guide mount in the four jaw and very carefully bored the entire displacer guide out to start over again.
I didn't have a reference location for the guide, so it was a matter of taking small cuts on the off center hole with a thin homemade boring bar, checking for concentricity with the walls as the they got thinner, and adjusting the 4-jaw. Finally when I broke through it was just a very thin foil all around and the bore was concentric. One step forward one step back!
The silver lining, or lemonade, or whatever for the messed up tapping is that it will now be a lot easier to make up a new guide and threaded bushing in the lathe before mounting them in the plate.
Post by: vtsteam on March 05, 2025, 08:33:40 PM
I just received a no-name 1/8" reamer, but I mic'ed it at .1260". I think it will cut larger. I'll have to try it on a test drilling to see if it's worth using. If not I'll make a toolmakers reamer from the pushrod stock. It's .1250"
Post by: vtsteam on March 06, 2025, 06:50:52 PM
I drilled the bushing in the lathe with a #31 drill (.120"), and then used the new reamer to bring the bore to size. Then it was time to thread the outside of the bushing 1/4-28. I don't have a tailstock die holder for my lathe (yet), and it doesn't have screw cutting capability (yet), so I used the expedient of squaring up one of my tool holders to the lathe ways, and using that to press against the back of a hand held die handle -- which kept it square to the workpiece. I rotated the chuck by hand, and wound in the leadscrew at the same time, which kept up square pressure on the die, and the threads came out nicely.
Post by: vtsteam on March 06, 2025, 07:00:11 PM
Post by: vtsteam on March 06, 2025, 07:05:53 PM
Post by: RussellT on March 07, 2025, 05:06:08 AM
I'm following with interest. What's the slot in the guide for? The original version didn't appear to have one.
Russell
Post by: vtsteam on March 07, 2025, 11:30:35 AM
It's just a slot for a screwdriver.
(The original was just one piece brass, silver brazed in place. Now it's threaded and two-piece.)
Post by: RussellT on March 07, 2025, 12:20:49 PM
It's just a slot for a screwdriver. :doh:
Post by: vtsteam on March 07, 2025, 12:40:54 PM
Post by: vtsteam on March 07, 2025, 08:37:27 PM
Total disappointment! I was all set to try out the new changes. But no go is no go.
So of course I tried un-ovaling it in the vise, and went about a thousandth in the opposite direction. Still, it was an improvement. The only course open at that point was to hope that lapping the cylinder would bring it back into round enough to try the engine out again.
It might mean making a new piston too though, since it will result in an overbore. Well, lapping first, and we'll see what we've got.
Post by: vtsteam on March 07, 2025, 08:46:10 PM
First I found an old 3/8" bolt. Cut the head off, and screwed it into a chunk of aluminum scrap.
Post by: vtsteam on March 07, 2025, 10:05:13 PM
Post by: vtsteam on March 07, 2025, 10:07:35 PM
Post by: vtsteam on March 07, 2025, 10:10:07 PM
Post by: vtsteam on March 07, 2025, 10:13:47 PM
Post by: vtsteam on March 09, 2025, 10:53:15 PM
Post by: vtsteam on March 09, 2025, 11:08:42 PM
The bore was eventually cleaned up back to round, with about a thousandth taken off. I reassembled the engine and there was still good compression, so I gave it a run this evening. It struggled to break 900 rpm, and at that speed I could hear some pretty loud clacking sounds.
Upon disassembly and checking parts, these noises turned out to be piston slap. The piston is definitely undersized now despite the good compression, and I could feel a fair amount of slap-stick when I exercised it by hand. Not surprising the engine couldn't run well.
As I figured, time for a new piston.
Unfortunately a couple hour search for the stick of graphite I'd had eighteen years ago when first building the engine turned up nothing. I know I still have it somewhere. Extremely irritating! But finally I gave up. I sent for another which will take about a week to get here. I know it will turn up again, some time after the new one arrives.
Never mind, I'll think about making other improvements in the mean time.
Post by: shipto on March 10, 2025, 01:21:43 PM
Post by: vtsteam on March 10, 2025, 01:40:23 PM
Post by: shipto on March 11, 2025, 01:29:01 PM
Dwayne, what kind of lathe do you have?Old Harrison 14" like https://www.lathes.co.uk/harrison/page18.html although mine is in a bit better condition.
Post by: vtsteam on March 12, 2025, 08:28:29 AM
Post by: shipto on March 12, 2025, 01:39:16 PM
Wow! That's industrial level. Very nice! :dremel: :thumbup:Thank you run by a 2.2kw motor on an inverter can make scrap in no time at all. :lol:
Post by: vtsteam on March 12, 2025, 10:42:23 PM
Post by: vtsteam on March 13, 2025, 03:40:56 PM
Post by: vtsteam on March 13, 2025, 08:42:45 PM
I don't think I like an aluminum lap. The engine had been originally built with a lead lap that I'd cast onto an arbor, then turned to size. It made a great lap, and the abrasive bedded well, and it gave a really nice finish but I don't like working with lead any more. So I decided to try a wood lap.
I had a turned piece of oak that I'd earlier used as an slip fit arbor for thinning one of the displacer cylinders. I turned this down to just undersize -- a tight slip fit really on the power cylinder, and then charged it with abrasive and kerosene (parrafin oil). Here's the lap as used, it took off lots of fine brass:
Post by: vtsteam on March 13, 2025, 10:19:27 PM
I could see a reflection in the finish:
Post by: vtsteam on March 13, 2025, 10:28:39 PM
Post by: vtsteam on March 13, 2025, 10:44:40 PM
Post by: vtsteam on March 14, 2025, 02:40:32 PM
Post by: vtsteam on March 14, 2025, 02:54:47 PM
But, no problem, we'll do it in the drill press.
I centered a chucked drill bit in a vee-block, then clamped a scrap of aluminum as a fence against the block. As long as the vee-block is tight to the fence, it will present its center to the drill bit. But it can slide along that fence. Then I clamped the graphite blank in the vee block, using a bit of cardboard under the clamp to protect the blank.
I checked the height of the piston slot to the drill table at both sides to ensure it was horizontal. Then I marked the top of the piston where I wanted to drill the journal hole the proper distance back from the end.
Then it was just a matter of sliding the Vee block along the fence until the mark was centered under the drill bit, and the hole was drilled.
Post by: vtsteam on March 14, 2025, 03:02:11 PM
Final step was to ream the journal to size and install the con rod.
Post by: vtsteam on March 14, 2025, 07:55:46 PM
Well we're definitely back in business with a good baseline again. I'm going to think about the displacer cylinder change. I think definitely there is more cooling now, and it extends further along the cylinder with the heavy aluminum flange.
I think the problem may be that I've got too much cooling now compared to the amount of heat available, which is relatively low. I don't yet want to add more heat though I will in the future. I think my next change will be to make a displacer cylinder with a thinner flange thickness, and that will be made out of stainless or rather than aluminum. I'm not sure about the copper cap. Probably revert to stainless again just to compare with my earlier cylinder #2 which was that best performing one.
Post by: sorveltaja on March 14, 2025, 08:27:21 PM
Anyways, I can't remember the exact steps I used to hone the cylinder, but on the last stage, I used automotive polishing paste with - perhaps brass or aluminum rod (that's what I had at that time), against brass cylinder.
It was rather tedious process, as I did it manually. I didn't use split rod to lap - it was solid. It used to get stuck in the cylinder, when I went too far, while turning it. Good knock on the working end was enough to release it. Finally, it moved through the cylinder.
Then came the final stage - to fit graphite piston to the cylinder. I used the same procedure as with lapping. Solid graphite rod (part of it was then used as a piston) against lapped brass cylinder (as graphite wears itself relatively easily through the friction, when compared to metals).
That's just one possible way to minimize power piston/cylinder friction.
Post by: vtsteam on March 14, 2025, 10:19:42 PM
Also interesting to hear about your lapping experiences. For me the dowel worked surprisingly well, I really hadn't expected it to do better than the aluminum lap.
I'm thinking that "aluminum" is actually a too general term for me to make judgements about-- aluminum varies a lot in hardness, and so maybe I chose a harder variety out of the scrap box. this time
Pure aluminum is dead soft, and I bet that makes a better lap. I think it's important that the lap get embedded with the abrasive, rather than it moving around between the two surfaces too much. The lead lap I used years ago worked very well, and I know the abrasive embedded deeply there. Same thing for the wood lap this time.
I have a pretty good honing rig for larger cylinders in a larger engine, which I'm hoping to start at some point in the future. It will still need lapping, too as a hot air engine, but it should have a uniform bore after honing, so only will need to be lapped for a good finish. That's my hope anyway.
Post by: vtsteam on March 14, 2025, 10:38:21 PM
It stands to reason that if the rest of the engine had rusted in a damp garage for 8 years that maybe the bearings might have some issues, too. Well, those are easily replaced, and I now have ABEC 9 bearings on hand. The ones in place were ABEC 7.
Another possible contributor is the main shaft. It's 5/16 (.3125") but the bearing takes an 8mm shaft, so there's a little play. I have some 8mm stainless steel now, so I'll make the switch when I change the bearings.
A third issue I noticed: I washed out the power cylinder before reassembling again tonight, and when giving the flywheel a spin, I saw a little moisture from not having dried it completely squeeze out from the edge of the cylinder where it seats in the base plate. This means a leak. Easily sealed with a little bearing compound -- Loctite 620, but good to know. It's probably always leaked, so that should help performance when fixed.
Fun stuff! :dremel:
Post by: vtsteam on March 15, 2025, 09:30:06 PM
I put some marker on the flywheel hub, spun it some more. Taking it apart again, I was able to see the high spot where it had removed the marker. I filed the raised bit down with a small triangular file, and the noise. was gone.
Post by: sorveltaja on March 16, 2025, 07:27:00 PM
Hey sorveltaja! :wave: :beer: Great to hear from you! How is your guitar? That was such an interesting project! :coffee:
Yeah, that guitar is ok, except its tremolo turned out to have a flaw. Tension of the strings has caused string retainer to rotate(something I didn't expect), and therefore it isn't possible to tune it properly.
Post by: vtsteam on March 17, 2025, 10:53:08 PM
re. No. 83, I started on a fourth displacer cylinder today.
It features a thinner steel flange, compared to the last version's thick aluminum, and a reversion to a stainless steel end cap instead of a copper one. I wanted to try go back to the performance of my second cylinder, if possible, by removing some of the added variables.
So far, I've made 4 displacer cylinders, lined up here to show the differences. The first was just stainless steel tubing. Top RPM was around 800. The second had a thinned down wall thickness, and average speed was around 1400 RPM it did hit 1600 rpm on one run. The third cylinder had a changed mounting method. Instead of passing through the aluminum heat sink, it had a flange and mounted outside of it. It ran about 1300 RPM. An improvement in bearings and a sealed leak and removal of a frictional interference produced a max speed of 1440 RPM.
The 4th is a reversion to the second cylinder but with a flange mount.
Post by: vtsteam on March 22, 2025, 07:15:14 PM
I'm really happy to say the new mini electrical heating furnace works really well with the engine. And with less power than I thought it might take.
The engine starts and reaches a steady state at about 960 RPM at 80 watts @ 10.8V. That was on the porch outside my house at an initial test at a 53 degree (F) air temperature, and some fairly strong breezes.
I think it would probably run faster indoors, but I had to do this initial test outdoors to burn off the fumes from a small amount of tape and release agent used in originally making the coil.
Here's the engine running in a test:
Post by: vtsteam on March 22, 2025, 07:29:48 PM
Nevertheless, I did achieve 1050 RPM at about 100 watts and that speed was increasing slowly, but by then I needed to stop and bring everything inside, because it started to rain.
I'm very, very happy that this heater worked out first try with the amount of wire and power estimated. It was a long wait while it dried. I can now really compare modifications in the engine.
The engine is running fairly loud lately -- I think it's worn big end bearings knocking now. I've got definite plans for improvement!
Post by: vtsteam on March 23, 2025, 05:28:59 PM
Yet I'm seeing 2000 views a day on the progress of this little engine. and in the forum statistics on the front page right now, 500 visitors, and only three members signed in.
This is a rather sad state of affairs, and a forum like this will not continue unless others join, sign in, comment and, one hopes, even add interesting projects of their own. Certainly, now, I'm asking myself just who is it I want to communicate projects to? If it's just lurkers, bots, spiders and AI content reapers, then no thanks, I'd rather just work on my own.
Nope I'd rather talk with real people. Are there any out there in that group of 2000 views, or those 500 visitors today? Say something. Say hello. Say anything! Let us all who post here know that we have a reason to do so. Organic Intelligence. :mmr:
Post by: nickle on March 24, 2025, 06:10:54 PM
This is a very interesting project both technically and the back story. I’m really enjoying watching you problem solve and tweak this little engine. It gives me something to aspire to once I have a bit more space in my life again. For the time being though I am enjoying your build.
I’m checking in regularly.
Nick
Post by: vtsteam on March 24, 2025, 06:39:59 PM
I hope people do want to communicate on fora again, I also see the lapse of the last few years, and yes, probably videos have a lot to do with it. But there is no substitute for group conversation. We're humans (mostly), we talk, and we want to be heard.
I know I'm really not writing this stuff for show, I'm here to communicate, and hear from others what they are doing and are interested in. And I really don't care at what level that is, could be expanding an ant farm. Or fixing a trumpet. Great! Bring it on! :lol:
Okay so, I've been working on a side project temporarily, trying to rehabilitate some small cnc equipment I built a long time ago, and which has been attacked by time rust and mice (TRM) in my further shed. Definite hazard around here. And trying to get my head around what to do about the disappearance of the parallel port as a viable means of CNC communication, since both of the now dead old laptops I used for that did so with the contraptions I once built.
That's beside the point of this thread, and so tonight, not to seem to have become sidetracked completely, I ran No.83 on electric power for two trials, one with displacer cylinder #3, and one with displacer cylinder #4, both at 100 watts heat exactly.
The #3 cylinder (thicker aluminum base) was slower to heat and run up to speed, but ultimately edged out the #4 cylinder at top speed by about only 10 more RPM. In both cases the rod ends were annoyingly noisy, and I really want to replace the whole set ASAP with what I hope will be a big improvement all around. I think the #3 cylinder possibly peaked at RPM because of this mechanical mayhem, rather than actually reaching potential.
BTW the CNC machines are, I hope, going to give me a lost foam casting pattern for the heat exchangers cum base plates (hollow and water filled this time) for a high speed vertical shaft Rider variation on this engine -- using otherwise the same specs sizes and construction as No 83, for comparison testing.
It will be called No 84, of course.
Well okay one more thing -- I'm trying to rehabilitate my small melting furnace, too, after it got buried in snow this winter and spoiled the lining. So, that's four projects I'm doing at the same time right now. But that's a happy state of affairs for me...disorganization is life.
Post by: tom osselton on March 24, 2025, 06:52:37 PM
Post by: shipto on March 24, 2025, 07:08:35 PM
Post by: nickle on March 24, 2025, 11:18:46 PM
I need to get going on refurbishing my foundry too. Just gotta keep bringing up the kids and earning the cash for a while longer.
Keep posting your work. It’s great
Post by: awemawson on March 25, 2025, 04:00:46 AM
Not sure if it was changing forum software constraints or a choice by the team ?
Post by: vtsteam on March 25, 2025, 10:36:29 AM
Dwayne, Andrew, Tom, funny, I never used the "Like" feature when it was here because it required allowing online tracking scripts to run in my browser that I normally block. As a result I did not either see the likes (my own or anybody else's) or have available a "Like" button. Also, the best most lively time here was the time before likes. I think they ushered in the decline, it wasn't their removal that caused it.
But from a larger perspective, When I participate as a forum member, I don't want personal votes (which is what a Like is) I want conversations. To me, Likes are just one more way of automating communication. It doesn't take effort, and it doesn't do anything except kind of indicate popularity. You can look at hits on a topic to judge that, anyway.
I see a forum like a pub. A place where people talk. If they're not talking and just pushing buttons, there's no point to the forum. A forum's great strength compared to a video, is that it is an active form of communication, instead of passive. You can discuss things at length. You can ask questions. You can co-create projects. And it's focused on an area of interest, and presents things in a very readable way. Like articles in a collaborative magazine.
This combination is very different to anything else, and I'd hate to see this forum in particular disappear. It has a very egalitarian feel compared to others I've participated in. It has never been filled with "experts and dunces" or, "the right way and the wrong way." Rather there was always a deep respect for individuality and experimentation -- and that also is rare these days. This thread itself would not exist if I felt otherwise. This is the place for me.
Oh, one other thing about "Likes," you have to be a member, and signed in to push the button. There were 500 anonymous visitors the other day when I looked, and 3 members signed in -- one of which was me. I don't think likes are going to make a dent in that. I think good conversations and good will is.
People want to be around other people with shared interests.
Post by: Country Bubba on March 29, 2025, 09:22:43 AM
But being in my 80s, the number and type of projects is diminishing for various reasons.
BUT I do enjoy seeing how other people doing things and trying to learn in case I might ever need that type of info.
One great example is your other thread on the cnc controller!
Always enjoy your posts over the years!
Country Bubba
Post by: vtsteam on March 30, 2025, 12:16:37 PM
I have been down a rabbit hole of CNC and old computers so deep this last week, I was wondering if I would ever find my way out! :bang: :bang: :bang: :lol:
What a waste of time. Absolutely for sure I could have made by hand a hundred samples of what I want to make one of via CNC during this time. But I get stubbornly stuck on solving a problem, and I can't stop un til I eventually decide it isn't solvable, or I beat it.
I'm sorry I haven't continued with No. 83 in the meantime, but like I said, I was stuck on this nearly pointless set of CNC problems.
Ultimately, the problem turned out to be two bad driver laptop computers -- one with a bad keyboard and (after replacement) a bad system board, the other with a bad single memory location in low (soldered) memory on the system board, some messed up hard drives, and old programs. The problems which confounded those were the need for parallel ports by the driver boards, and Microsoft XP for one of the hot wire foam cutting programs. Finally, none of my existing foam cutting driver programs will cut the shape I want, since they are primarily geared toward cutting wings.
Okay, I've given up, trashed the two bad laptops, and written off the foam cutting programs. I'll either write my own, or (probably) just write G-code directly to do what I want to do -- which is basically simple shapes. I also might just make up a simple(er) and smaller hot wire foam cutter than the one I have since I am NOT planning to cut wings in the future.
Anyway, explanation above of why I am momentarily away. Back at this engine shortly again.....
Post by: Country Bubba on April 05, 2025, 09:06:42 AM
Some people call it progress, but I call it planned obsolescence and a few other censored words! :jaw:
There is a lot to be said when you build something from the ground up and know HOW it works so most of the time you can fix it.
Have a great day
Post by: vtsteam on April 05, 2025, 11:11:32 AM
Yes, I used TurboCNC for a long time, too. Shows you how simple CNC needs to be DOS and a few megabytes of code will do it.
I did finally get my foam cutter working with an old Thinkpad T43 with a parallel port. It runs Jedicut, for foam cutting under windows XP.
That laptop will probably run TurboCNC, too, for my gantry mill. I was mainly using LinuxCNC when the Thinkpad 600Es died. The T43 technically shouldn't run LinuxCNC because of a latency issue, but there is a possible workaround for that I may try.
Presently trying to convert the mill to arduino/grbl as detailed elsewhere on the forum. Hope to be finally off of this irritating CNC stuff and back onto No 83 again shortly.
Manual control, organic intelligence, forever! :lol:
Post by: vtsteam on April 08, 2025, 07:11:39 PM
If you could call it big. It's a 3mm bearing. I will have to re-pin the flywheel, since the former bearing was 1/8". I don't have any 3mm rod, so I'll have to turn down some 1/8". Well maybe grind it down with the lathe's milling attachment.
Post by: vtsteam on April 09, 2025, 08:10:14 PM
The old flywheel was steel, and possibly heavier than needed. I did like the way it looked, though, so rather then making a smaller flywheel, I switched materials to aluminum. That should reduce the weight by two thirds, yet still look the part. I hope this new wheel will have enough inertia.
Guess we'll find out! :ddb:
Post by: vtsteam on April 10, 2025, 03:53:02 PM
And that one also turned out to be a problem because the displacer just "ticked" the end of its cylinder. If I tried to adjust, it would tick at either the hot end, or the cold end. But never missing both. So that means the throw (and pin spacing) is just a tiny bit to large. I'll have to make another. :wack:
Heading out to the shop again right now. I want to have the engine running this evening. :loco:
Two down, one more to go:
Post by: vtsteam on April 10, 2025, 07:22:03 PM
The engine is much quieter and smoother. It starts running with the new lighter flywheel after 4 minutes of warmup (the electric heater at 100 watts is somewhat slower than Sterno was, I believe) and starts at about 700 rpm, gradually increasing as the furnace heats up.
There seem to be stages of steady rpm, then increases to higher levels, where again it stays relatively consistent for a time before increasing. Maybe its some set of resonance levels. There's a fair amount of vibration (for a small engine) and I notice that if I place my hand on it to steady, I can sometimes get an increase in RPM.
I think balancing the crankshaft might help top speed, but not sure how to do that with an inline twin with a 90 degree phase difference.
Anyway, here it is with new flywheel, new power piston conrod (ball bearing big end), and new crank arm:
Post by: nickle on April 10, 2025, 08:42:08 PM
Post by: vtsteam on April 10, 2025, 10:04:21 PM
I'm reading up on balancing now. Lots of theories -- mostly similar for singles -- a certain percentage of the reciprocating weights plus the rotating weights added to a flywheel. What they don't say is how big is the flywheel and how far out the weights -- in other words, no mention of the arm.
I have a 600 pound Listeroid diesel single with two 24" flywheels powering a generator for emergency outages. Believe me, that is vibration! Yet I balanced it to the point where I don't think it is going to tear down the shed it is housed in any more. It seems quite tame actually. No math involved.
To balance, I set it on railroad ties atop a 2" rubber horse stall mat, then filled in around the ties up to level with gravel. That's like a spring and shock absorber in a car sort of. That's not balancing, but it allowed me to begin after steadying it that way so it wasn't walking around. How I balanced it was just holding a piece of chalk close to one of the flywheels near the top so that it just contacted the chalk during a major excursion. This marked the flywheel at the point of major unbalanced thrust in that direction.
Then while the engine was stopped, I picked a point 180 degrees opposite on the flywheel and added modeling clay there. I started the engine again and checked with chalk again. Less movement, but still some. It was marked in the same place, so I added more clay opposite. Eventually the excursion was nearly gone, and I called it done. I checked the other flywheel the same way. I epoxy glued on equivalent weights to the clay for a more permanent solution.
Post by: vtsteam on April 10, 2025, 10:24:09 PM
Post by: awemawson on April 11, 2025, 02:41:27 AM
Post by: vtsteam on April 11, 2025, 09:57:38 AM
If there was a one day project already posted by someone else, cheap, I'd build it!
If you're in the mood to take on an electronics challenge......?
(Probably no time, I'm guessing, due to landscape, livestock, and guest, infrastructure support :whip: )
Post by: vtsteam on April 11, 2025, 10:24:16 AM
Thus portable between engines.
Apply in the direction of the axis of interest.
Anybody out there up for that as a project to post here on Madmodder? Come on, you know you can do it! Think of the glory! :lol:
Post by: awemawson on April 11, 2025, 10:26:20 AM
Post by: vtsteam on April 11, 2025, 10:28:30 AM
Post by: vtsteam on April 11, 2025, 11:11:39 AM
Performance appears to be 300 RPM better than it had been before the changes to flywheel, con rod and crank link, when tested at 100 watts.
I'm going to let it cool down and change displacer cylinders to the one with the thinner steel flange and copper end, and test again. :coffee:
Post by: vtsteam on April 11, 2025, 12:22:18 PM
Unfortunately, due to double variables (flange difference, end material difference), there is no way of telling specifically why this cylinder is better. Just that it is better, by close to 100 RPM, than the other. Tch tch, mixing variables. :wack:
Oh, also, it did the same thing -- ramped up at "rpm levels" and responded to a steadying hand pressure by increasing revs.
Post by: vtsteam on April 11, 2025, 06:46:20 PM
Post by: RussellT on April 12, 2025, 05:01:05 AM
steadying hand pressure by increasing revs.
Have you tried clamping it down to the bench?
Russell
Post by: raynerd on April 13, 2025, 04:17:09 AM
Well it's kind of disappointing to see the very small amount of interest most visitors to the site pay to people posting here. Other than a welcome few comments from old friends, it's as if we were alone.
Yet I'm seeing 2000 views a day on the progress of this little engine. and in the forum statistics on the front page right now, 500 visitors, and only three members signed in.
This is a rather sad state of affairs, and a forum like this will not continue unless others join, sign in, comment and, one hopes, even add interesting projects of their own. Certainly, now, I'm asking myself just who is it I want to communicate projects to? If it's just lurkers, bots, spiders and AI content reapers, then no thanks, I'd rather just work on my own.
Nope I'd rather talk with real people. Are there any out there in that group of 2000 views, or those 500 visitors today? Say something. Say hello. Say anything! Let us all who post here know that we have a reason to do so. Organic Intelligence. :mmr:
It is a really sad fact. It seems everywhere is quiet. I thought people may have moved to facebook groups but there is sod all on those as well. I remember back in 2009-2011, you could post a picture at 9am in the morning and you`d have a hand full of replies and comments by midday. I don`t know what has happened. I think it is quite self for filling as well- the less people contribute, the less it makes me contribute. I`m not very skilled and learnt everything from this forum and its users when I was really getting into engineering. I use to comment on the comments based on something interesting someone had said, as much as replying to the poster. Discussions spiralled. It is why I started making my little videos but it is all because I enjoy doing it, feedback is minimum.
Hopefully it`ll come back around and people will start posting more.
Your engine is looking great and I`ve enjoyed the pictures :D :mmr:
Post by: vtsteam on April 13, 2025, 11:55:26 AM
I also learned a great deal of what I now can do participating here over the years. When I started on madmodder I got a lot of help from the late Rob Wilson, and tons of encouragement from the late Dsquire. The loss of some of us due to attrition might be a factor, too, sadly.
I think during the last five years or so, YouTube has substituted for fora, and I have a few videos there myself. But it's a very different experience there -- basically passive and disconnected other than brief comments and likes. A forum is a very different animal. It is communication, and a group atmosphere. Shared progress through projects. Frankly, it's more fun -- at least to me.
Anyway, on the positive side of things, I'm seeing more new member requests, and a fair number of views here, so let's keep talking and going! :nrocks: :headbang: :coffee:
Post by: vtsteam on April 13, 2025, 11:57:16 AM
steadying hand pressure by increasing revs.
Have you tried clamping it down to the bench?
Russell
Heh, nope, Russell! :lol:
Post by: vtsteam on April 13, 2025, 08:04:09 PM
Today I started making a little latch for the fire door on the firebox. I also began insulating the firebox. It will be insulated just like my melting furnace, but on a tiny model scale.
Here I've fitted a layer of fiber insulation to start with:
Post by: vtsteam on April 19, 2025, 10:13:18 PM
Back at it shortly.......