Author Topic: Bog's Paddleduck Engine (Read 99093 times)

Darren · « **Reply #75 on:** May 19, 2009, 06:59:16 PM »

Looking good....

Which reminds me, I must get back to mine......just letting you show me how...

I believe Shred who has just joined us is building one too?

bogstandard · « **Reply #76 on:** May 19, 2009, 08:02:21 PM »

Kirk,

I have got the bits for you, and will get them away next time the wife takes me out.

It is starting to look very impressive and well made. It is a fairly large engine at normal size, but yours will be a monster.

John

kvom · « **Reply #77 on:** May 19, 2009, 08:40:14 PM »

I have two questions about the slots that connect the steam ports in the steam chest and cylinder.

1) There are dire warnings about going over the "line". I know the cylinder ports are close to the top/bottom of the block, but as long as the slot doesn't exceed the bottom edge it doesn't seem there would be a "leak". Am I missing something?

2) Would it not be equivalent to mill slots in the block?

I plan to follow the plans, but am interested in the whys/wherefores from curiosity.

On another topic, I am currently taking an evening course in CNC lathe programming. I will be making an actual part on the Haas SL-1 lathe lather this week as the culmination of the coursework. Over the summer I will be continuing, taking a course that will involve more programming and making more parts. Rather than use the canned exercises, I have the opportunity to design my own class projects, and so will be making the columns during the class. I should be able to come up with simething that would be hard to do manually.

bogstandard · « **Reply #78 on:** May 20, 2009, 12:50:37 AM »

Kirk,

You are quite right, you could cut the slots in the block. You have to visualise how I made this engine. There were no designs or plans for it, it was a matter if making the next bit to fit onto the previous piece made, only going forwards, with very little planned for going back to a previously made piece, hence the slots were put onto the part that was made at the time.

With regards to coming close to the edge. I made this engine to be an easy exercise, so no complicated gaskets to cut, with everything being sealed with a liquid gasket compound, which works much better when no very thin lands are used, so hence, don't go beyond the line as you will start to get into 'blowout' territory.

If you think that by cutting slots into the block would be better for your build, then please do it. Nothing is written in stone, and as I said, I was making it on the run, and as such some things will defy general logic.

You are quite right in querying some of the ways I did things, and proves you are thinking about what you are doing rather than doing a 'lemming' build. But as proved by myself, and other people, the engine will run if built as directed.

I think if I went back to it, and really looked at the design, I suppose I would have done a few things a little differently, but hey!, it works!, so being as lazy as I usually am, I left it as it was.

It was the same when I did the refurb on that Marcher steam engine, I found some glaring mistakes in John Bertinat's plans for it, but the engine works if built from plans, but would run a lot better if some slight modifications were done to his instructions and plans.

John

John

kvom · « **Reply #79 on:** May 20, 2009, 08:06:44 AM »

John,

Thanks for confirming my thoughts. Personally I think the design is really interesting, and I believe I can see how you developed things as you went along. That said, there was obviously a great amount of looking ahead, and certainly your experience in both engines and machining went into the process, whether conscious or not.

It seems to me that the slot in the block will be better/easier/safer. You can start the slot at the height of the steam chest port and use the inlet hole on the block as the "stop point".

One other factor that makes this build enjoyable is the nice mix of milling and turning.

kvom · « **Reply #80 on:** May 21, 2009, 02:43:49 PM »

Today I decided to make the upper plate, as I had limited shop time available. I started with a 4"x4" piece of .25" thick brass plate that had been flycut on one face. After squaring the sides I used a 1/8" endmill to saw the short side, then used an endmill to bring to the final dimensions.

Since all of the holes are or can be referenced from the center, drilling them was an exercise in cranking the handles and watching the DRO. I drilled all of the mounting holes to take 6-32 screws. The large holes for the glands needed to be slightly over 1" in diameter. I used a 3/4" end mill (my largest) to make the initial hole, and then the boring head enlarged them to ~1.05 (loose fit arounf the gland).

I didn't make any cutouts as I want to see how the plate looks when mounted before deciding on any blingification.

As I was taking the photo UPS arrived with my 3/8" drill rod, so machining the valves may be the next task.

bogstandard · « **Reply #81 on:** May 21, 2009, 03:42:59 PM »

Quote

One other factor that makes this build enjoyable is the nice mix of milling and turning.

Actually Kirk, the first proviso on the build was that it could be machined completely on a lathe with a vertical slide. Having a mill would be a definite advantage, but not essential. Hence no difficult angular port drilling normally associated with an engine of this type.

On your last post, don't forget to give yourself a bit of 'wobble' clearance on the crosshead support holes. I was a little lax in getting my crosshead holes in the right positions, and needed that adjustment to get the engines to run.

John

kvom · « **Reply #82 on:** May 22, 2009, 09:55:46 PM »

A full afternoon's work in the shop resulted in exactly one useable part:

The two other valves that I started ended up in the scrap bin because of various operator errors. On the positive side I did learn the best way to turn this rod to get a better finish, and I can probably make a valve in less than half an hour if I don't mess up.

I decided that the lathe karma was lacking, and decided to move to the mill for a "simple" piece, the blanking plates. Well I messed up there somehow as the holes didn't end up centered. So I figured it was time to call it a day.

As for wiggle room, I think I need to plan for that on the steam chest/blanking plates. I drilled the holes with a #20, which is a close fit for an 8-32 screw. Using the DRO to drill the holes for the plate, I found that the screws would "just" go through the plate and the steam chest. I plan to enlarge these holes by a couple of thousands so that when attached to the block I will be able to wiggle them slightly in case the bores on the block and steam chest are not perfectly aligned.

bogstandard · « **Reply #83 on:** May 22, 2009, 11:22:43 PM »

Kirk,

There is no shame in making wiggly holes, as long as they are not seen in the finished article.

You can sometimes strive too much for precision fits. On mundane items like mounting holes, give yourself a break.

John

kvom · « **Reply #84 on:** May 23, 2009, 04:14:45 PM »

Here's the summary pic of today's progress:

Got the other valve made, although it took longer than the hour I estimated yesterday. I also reamed the steam chest bore to .375" to match the valves. Of course now it's a press fit at best, so some lapping is due there.

The same is true for the block, where I re-reamed the bores to .5" to remove the burrs caused by drilling the steam holes. I then drilled the holes on each end for attaching the steam chests. The afternoon finished with turning the pistons, which are likewise a press fit and require lapping.

kvom · « **Reply #85 on:** May 26, 2009, 09:54:20 PM »

I had a couple of "days off": Sunday my daughter had invited 15 or so of her closest friends to have a party to celebrate the end of the school year, as well as to inaugurate the playroom upstairs from the stop. Dad was "politely" asked not to run any noisy machines during that event. Monday we had a long afternoon invite with some friends. But today I had most of the afternoon to play in the shop.

The first task was to turn the top caps, after which I drilled and tapped both them and the block. I also tapped the mounting holes for the upper plate, allowing a test fit:

I then made a pair of blanking plates and tapped the mounting holes in the block. The DRO did manage to get the holes in all three parts to line up, so I was able to screw them all together. The only "glitch" is that one of the valve holes is slightly obstructed by the plate, but taking apporx .01" off that end should solve that.

Since I had the top section chunks lashed together, I was interested to see how it would look connected to the bottom. I'm going to make the columns during the summer CNC lathe class, so I decided to quickly make a set of plain columns from some 3/4" Al round I had previously scavenged. I had only enough time to finish two of them:

The soda can is included as a size reference.

Now it's time to get cranking on the crankshaft.

bogstandard · « **Reply #86 on:** May 26, 2009, 10:41:15 PM »

That is going to be a monster of an engine Kirk.

I personally would leave things like decorative columns etc until you have proved it will run. No use going to a lot of trouble if one of your calculations is a bit far out and stops it running.

But don't think negative as I am doing, just carry on and I am sure you will have a great runner.

John

kvom · « **Reply #87 on:** May 27, 2009, 08:51:00 AM »

My thoughts are to make the columns a bit longer than spec, so that it is easy to shave off a bit where necessary. These temporary ones are .1" longer than the plan would indicate, but since the thickness of the top plate isn't given I can't be sure what the optimum length will be. I can also mill the top plate thinner as well.

bogstandard · « **Reply #88 on:** May 27, 2009, 09:12:03 AM »

Both top and bottom plates are the same thickness.

John

kvom · « **Reply #89 on:** May 27, 2009, 11:10:15 AM »

Quote from: bogstandard on May 27, 2009, 09:12:03 AM

Both top and bottom plates are the same thickness.

John

They are on mine as well. Hiowever the thickness of the bottom plate has no effect on the mechanism. As I understand it, I can adjust the travel of the valves and piston via the threaded connections, but if the plate is too thick or the columns too long then you run out of adjustment room and must reduce the height. Correct?

bogstandard · « **Reply #90 on:** May 27, 2009, 12:27:51 PM »

Sorry Kirk,

You are perfectly correct, but not a lot. About 0.050", it is there mainly for final tweaks to adjust for for piston and rod length mismatches.

John

kvom · « **Reply #91 on:** May 27, 2009, 12:49:54 PM »

Very soon I will be needing to get all the sliding fits working, and there are a lot of them (valves, pistons, bearings, conrods, piston rods, crossheads). I don't have over/under reamers, so all the holes for these parts have been reamed to same size as the part that slides through them. On my previous engine I had only one valve and one piston/piston rod. My "technique" was to use emery cloth on the sliding part until it could enter (albeit tight), and then use toothpaste to lap it to fit. So far I have done that somewhat with the bearings using some short pieces of drill rod. Is there a better approach?

Also I am wondering if reaming out the crosshead bores to the next drill size would be OK, as opposed to lapping?

bogstandard · « **Reply #92 on:** May 27, 2009, 02:37:55 PM »

Kirk,

Remember, this engine was designed for beginners, and as such, if the fits aren't very good, it will still run perfectly satisfactory. Just get it fitting to the best of your ability. Reaming to size for the matching rod will be perfectly acceptable.

In fact it is only on engines like flame lickers and sterlings that very fine tolerances have to be adhered to, purely because they have so little power, waste one tiny bit thru leakage, and they just won't run.

If you can get nice sliding fits on all parts, that will do. By the time the engine has a few hours on it, all those superfine fits will be lost anyway. If you can get the bits to fit together and turning without rattling or wobbling, you are onto a winner.

For the bores, if the piston will enter from both ends, and with a bit of oil in there, seal over one end of the bore, and pull the piston out of the hole. If it comes out with a pop, it will be just fine.

The only critical parts are the piston valves, they need to be lapped with a bit of brasso or toothpaste, but I have also seen engines running perfectly well with steam coming out of the top and bottom of the piston valves from new. The Wilesco range is a very good example, like they were made by cavemen with stone tools, but they still run OK. A tight fit on those engines would be about 0.002" clearance between the parts.

John

kvom · « **Reply #93 on:** May 27, 2009, 06:44:10 PM »

I finished the other two temporary columns this afternoon, and started on getting the sliding pieces to fit. First up were the bearings. Here's my alignment/lapping setup:

I ran it about a half hour with the toothpaste, cleaned it up and oiled it. The drill rod turns pretty smoothly now. I then did a bit of catchup by drilling and tapping the holes for the setscrews on the eccentrics. Next I lapped the bores of the crossheads in the same manner as the bearings. I discovered that one of my crosshead guide bars was slightly bent, so that's a job for another day.

kvom · « **Reply #94 on:** May 28, 2009, 12:41:16 PM »

John's shipment of solder arrived today. Thanks very much. Now I need to get on the ball and get the other necessary items.

bogstandard · « **Reply #95 on:** May 28, 2009, 02:38:16 PM »

Half to practice with Kirk.

The other half to do the job.

John

kvom · « **Reply #96 on:** May 28, 2009, 10:15:12 PM »

Other than making the other three crosshead guides this morning, I made no engine progress.

I spent most of the day helping a friend move his machine shop gear. He gave me his shop press, all but the hydraulic jack, and it's sitting on my trailer in my driveway right now. He also has a shaper attachment for a BP mill that I can have. I have no idea how to run it, and it's heavy. I believe it mounts on the opposite end of the ram from the head and will cut slots and the like.

kvom · « **Reply #97 on:** May 31, 2009, 07:32:05 PM »

I had the afternoon to play in the shop, and worked on getting the crankshaft and its attachments done.

The assembly does turn without binding, although I don't have the bearing blocks clamped down really tight. I discovered that I need to enlarge the central baseplate opening slightly, probably .01", as one of the crankwebs is hitting the corner.

If I can get the conrods finished next I can connect up the crossheads and get them lapped in.

DeereGuy · « **Reply #98 on:** May 31, 2009, 09:09:20 PM »

Kvom, your doing a bang up job on this engine and I can't wait to see more progress. I told John the other night that this engine is on my short list. I just may give this a go after I finish the Webster.

Bernd · « **Reply #99 on:** May 31, 2009, 10:04:43 PM »

Lookin' good there kvom.

Bernd

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Author Topic: Bog's Paddleduck Engine (Read 99093 times)

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