Scott Vacuum Engine......

[vtsteam]

Nice work David! 

[Stilldrillin]

Very nice. Good work.
Just as a thought if you ever need to do another is seamless pipe. I used some sch10 316L when making an exhaust manifold. It's a bit more expensive but has no seam to worry about.

Thanks Lee.
That's good to know. If I ever have to do another....... 

Nice work David!   

Thanks Steve.
It's good to see you back among us, again...... 

David D

[krv3000]

 

[Stilldrillin]

Thanks Bob.
Any/ all encouragement, gratefully accepted.   

Now, waiting for my pal Dave, who's a whiz with a bore grinder.

Here we go...... Arrived, this evening.   

Lovely bore........




Thanks Dave! Yer a gem! 

David D

[Stilldrillin]

Time to tackle the cylinder head.
From a piece of 8mm stainless plate, 100mm square. (Room for a spare. If it all goes pear shaped).   

It was at, (only), this point, I realised I am not as young as I would like to be........




Several rests, and the following day. It was free.......




I usually knock the corners off, by friction turning. In my mini lathe....... No chance! 

So, I mounted it in the r/t. And milled it roughly, round.........




Normal lathework followed. Finally finishing the o/d between blocks.......




The new head fits as a cap, over the cylinder flange. Giving .150" extra headroom, for a thicker graphite piston crown......




Looks rather nice, like this. Seems a pity to go poking holes into it.......




Twin port! Because the new shim blade, was occasionally sucked into the full width original port........




Inside.......




Much shorter inlet passage. Less heat absorbed into the head. Mebbe........




Shouldn't rust in there, now........




Thanks for looking in! 

David D

[vtsteam]

Verrrrry nice David!!

[Will_D]

Quote "Normal lathework followed. Finally finishing the o/d between blocks......."

So you are just using the friction of the two plastic blocks to keep the head centred?

Any extra friction material used?

BTW what is the yellow plastic?

Very nice work

Will

[Stilldrillin]

Verrrrry nice David!!

Thanks, Steve! 

Quote "Normal lathework followed. Finally finishing the o/d between blocks......."

So you are just using the friction of the two plastic blocks to keep the head centred?

Any extra friction material used?

BTW what is the yellow plastic?

Will

Hi Will.

Yes. Just friction.......

On this occasion, the disc is nipped between the two blocks. Trued, while rotating, by a piece of wood, held between toolpost and workpiece. Then full pressure applied by tailstock........

The driving block, is faced with a layer of insulating tape. The tailstock block, is slightly relieved in it's centre area.

Dunno about the plastic!   We used it at work, to make buffer bushes, in our rock drilling hammers. It might be the same as gas supply piping.......

No need for plastic. Wood will do just as well, as the driver. With a metal "saucer", in the live centre.

Very nice work.

Thank you! 

David D

[Stilldrillin]

Steps forward...... Steps backward. But, overall...... 

Mounted the original c/i piston, on a handy piece of curtain pole, and reduced to fit the new bore.

About -5thou from original.......




Assembled. But couldn't get the engine to spin freely. Seems the open end of the bore is a little tight. 

So...... Turned another length of curtain pole, to a sliding fit. (After sanding off the fuzz)........




Coated in fine grinding paste. And oscillated for 30mins, or so.......




Seems Dave has gripped on the end of the cylinder o/d, in his industrial machine, and triangulated it! 

Re assembled, again. Piston/ bore, dry, no oil. shouldn't pick up. Just a quick test run.

Twin temporary burners, this time.......

Now, I'm confident to carry on modding, to finish, as planned. 


Except......

An hour after running. The piston was stuck in the bore. Again!

The dreaded, condensation rust.........




Sheesh........




Pleased, the lap is still mounted in the chuck. I can polish the bore, for the new graphite piston.

Winter's closing in, on old bones. Not much will be happening this week.

Thanks for looking in!

David D

[sbwhart]

"O WOW"   indeed   

Its getting there Dave

 

Stew

[Stilldrillin]

"O WOW"   indeed   

Its getting there Dave

 

Stew

Thanks Stew! 

Considering, it was only loosely lashed together. I was very surprised, how it took off!   

I had three runs, as shown. Each time, (I guess), the condensation slowed, and stopped it.

Will first, heat up with hot air gun, or fill with hot water, in future. 

It's all a learning curve........   

David D

[vtsteam]

My take on vacuum engines:

There's two things happening that make for condensation: one,  the cylinder walls are below the boiling point of water. And two: combustion of conventional fuels produces C02 and water. So that water necessarily gets into the engine when the flame burns inside the cylinder.

Power in a vacuum engine occurs because those gasses are cooled by the cylinder walls and the gas contracts. So one way of increasing power is to cool the heated combustion products more quickly -- in other words a colder cylinder.

But the problem is if the cylinder wall is cooled below the boiling point of water, you get condensation on the cylinder wall, and that acts like a brake. Particularly if the clearance is close, and if there are no rings or grooves in the piston where the moisture can go to clear the bore.

So I'm wondering if grooved pistons would help reduce friction when there is a lot of cooling and a close fitting piston.

The other way of increasing performance is to introduce a hotter gas, and let the cylinder run hotter than the boiling point of water. In that case there should be no condensation, once an engine warms up, and it should run freely. This would require a hot flame, high flame volume, and a lower efficiency cylinder cooler. The cylinder should be as cool as possible, while still somewhat above the boiling point of water. A much higher temperature than that is unnecessary and would just reduce power.

Anyway, just some ideas....

[Stilldrillin]

Thanks for your thoughts, Steve. I like the idea of piston grooves, to hold the initial condensation....... 

The shop temp was only some 8*, if that. And it was only a quick proving run.
The cylinder and piston need to be nearer the 100* mark, at the start of future tests.

Next job, is the graphite piston. When the weather is a bit kinder to me old joints.......

David D

[vtsteam]

David, I thought of grooves only because I thought I remembered the oil scraper ring in an IC engine doing sort of the same thing.

I can't remember whether they might even drill through some IC pistons at the groove to clear oil

[Stilldrillin]

A piece of s/s, 2mm x 75mm square, (£2. Ebay), was made into a piece of 55mm dia. round.

Drilled, to match the cyl head........




Recessed, 25thou deep, for shutter blade........




Window, cut out........




Piston's eye view. The top of the blade can bend outward, to relieve any unwanted pressure........




I assembled, loosely, no oil. Still with the c/i, (now undersize), polished piston.

Had a bit of a surprise, during engine warm up. It runs, on the hot air gun! 

 

Official trial video........

I think the next job, aught to be the twin wick burner. 


Thanks for looking in!

David D

[SwarfnStuff]

Nice work again, as usual David.
 Perhaps you have discovered a technique for drying these little things out to prevent rust? I realise that you have gone with a graphite piston but the bore would benefit from some hot dry air I think.
John B

[vtsteam]

That's a neat discovery that it runs on hot air, David.  And the slide valve is very pretty work!  There is no condensation problem with hot air. One could finish a run with a hot air blower and put it way dry, if rusting materials were still used.

[Stilldrillin]

Nice work again, as usual David.
 Perhaps you have discovered a technique for drying these little things out to prevent rust? I realise that you have gone with a graphite piston but the bore would benefit from some hot dry air I think.
John B

Thanks John! 

I'm sure, the condensation problem was caused by the sheer mass of the cold engine, at English temperature.

Once the castings have been warmed up, by another heat source. There is no problem with the flame doing it's job, of only running the engine.

There's no drying to do, after a full run.

There's no graphite piston made, just yet. I must be sure of the bore's accuracy, before I machine that precious, (rare), piece of graphite.

That's a neat discovery that it runs on hot air, David.  And the slide valve is very pretty work!  There is no condensation problem with hot air. One could finish a run with a hot air blower and put it way dry, if rusting materials were still used.

Steve.
I was surprised! Only cycling the engine, to introduce heat inside the cylinder through the ports. I realised it was trying to run..... 

I'm sure there would be no problem with rusting with the original materials. If a warm start up, and long run could be arranged, every time. 

Thanks for your interest Fellas! 

David D

[awemawson]

David, if the piston goes pear shaped I'm sure that I can find another piece for you, so don't 'turn in fear'

Have a good Christmas

[Stilldrillin]

Thanks Andrew. You're a gem!

I intend to turn a plug gauge. Now that the bore has been lapped again. Still not sure, if the slightly triangular portion is ok...... 

Very best wishes, from Derbyshire.

David D

[fcheslop]

Hi Marra, nice to see her coming on well
I find a large bushy flame the best and I try not to use meths as it has more water and the dye 
Try to get some Shellac thinners also these fuels are hygroscopic so may contain more water if old

[vtsteam]

A carbon monoxide (CO) fueled flame would be best, and would produce no moisture at all since it contains no hydrogen.

But not too good a fuel for other reasons! 

(you'd want complete combustion to CO2.....)   

[Stilldrillin]

Hi Marra, nice to see her coming on well
I find a large bushy flame the best and I try not to use meths as it has more water and the dye 
Try to get some Shellac thinners also these fuels are hygroscopic so may contain more water if old

Heyup Mate. Thanks! 

I've not located any shellac thinners. The few times I've looked.......

I'm using denatured alcohol, these days. Burns cleaner than meths. (Even though Wilkinsons sell it as cleaning, meths)..... 

Wondering, if I can make a wick, "trough", between the two ports. Like a Bowman burner.....

David D

[Stilldrillin]

A carbon monoxide (CO) fueled flame would be best, and would produce no moisture at all since it contains no hydrogen.

But not too good a fuel for other reasons! 

(you'd want complete combustion to CO2.....)   

Steve.

I don't think I'm going to achieve that, using a wick and meths........ 

The condensation moisture problem is now sorted.
And the condensation rusting, will also be sorted when I make the graphite piston. 

Probably!

David D

[lordedmond]

At David D location partner eg Stanton of Stanton And Staveley
We used to burn CO in the main boilers for the alternators about 18 mega watt total , it was the waste product from the blast furnaces ,it was also used the fire the coke ovens to make the coke for the said furnace
Boy was it nasty stuff got your knees first so you could not get away

It was use at David D location to power the gas engines to get the the 2volts doc for the salt cells to get the chlorine gas this was then burnt with H to get hydrochloric acid vapour

Anyway nice work on the engine David and a happy new year to all
Stuart