Hot air and stirling engines

[Ian S CParticipant @iansc]

Hi Mark, used the Ross Yoke motor, Its slowly comming up in power. I’m starting to prepare it for pressurization. Got to design a seal for the bearing. I want to make a fitting for a pressure gauge, and go to the local tire repare shop for a valve stem and valve, not a lot more than that, although I’ll make a flywheel so it can have its own one.
come on out , tomorrows good, tuesday on I hope to be busy building bale feeder machines (we’v got one on order, hope for more, mabe half a dozen). Ian S C

[Mark Smith 3Participant @marksmith3]

I finally got the Ross yoke engine to go. But not as a complete ross yoke. I combined the cylinder from my pressurised engine to half of the Ross yoke. I made a new rocker arm that extends to the same level as the the upper arm of the Ross yoke to  drive the displacer, ignoring the bottom half. The engine is now a Beta design and runs well on meths and three times as fast on gas. I think that as an alpha or rider engine the capacity of the cylinders was too small to drive that size of yoke. The engine as it is now is 3cm bore and  two cm stroke. Just have to make a proper cooler and heater instead of a pair of wet underwear wrapped around the cylinder and a simple meths burner for the hot end.

When I make some better looking parts I will post some pics.

Mark

Edited By Mark Smith 3 on 05/04/2010 04:49:36

[Ian S CParticipant @iansc]

eThe main Thing Mark , it works, and thats the idea. My engine has a yoke with 2 1/4″ between centers of the cylinders, and a crank throw of 5/8″, giving a stroke of 11/16″, the cylinders are 35mm dia. Never tried the wet undies cooling system, sounds interesting, havn’t hooked up my cooling system yet, it just needs two of rubber tube fitted and some water, but when stored I like it dry, and it’s not easy to empty the water jackets(one each cylinder).
Anytime you want to come out just let me know, my time’s my own- usually. Ian S C

[Mark Smith 3Participant @marksmith3]

Could be this sunday Ian I’ll ring. Still can’t get your email to work otherwise I’d Chit Chat there instead of on the forum, which I doubt is its purpose; perhaps a general chat thread might be an idea??? By the way my first successful engine was cooled with the wifes underwear seemed to work a treat until I put a waterjacket on it; then I gave them back to her

Mark

Edited By Mark Smith 3 on 06/04/2010 06:11:22

[Ian S CParticipant @iansc]

Sundays OK, I’ll be here after 11am. Trying to think of some thing to say about the last bit, but proberbly I should’nt, i’v got to play bowls against/with Louise.
My motor will run for at least 2hrs without a cooling system, and today I lit it up and it started to move on its own, I don’t expect it to move fast enough to start itself. Ian S C

[Ian S CParticipant @iansc]

I,v made a side for the non flywheel side of the crankcase of the Ross Yoke engine(part of the sealing process), when held loosely against the engine when running it clatters against the engine, I wonder if I fitted a snifter valve, would the engine pressurise its self? Ian S C

[Ian S CParticipant @iansc]

Not sure how we’ll do this, but we’v got a wheels and wings event at the local airstrip(DC-3, P-47Mustang, balloons gliders etc., and classic cars ie VW Combi and other classics).Ian S C

[Gordon WParticipant @gordonw]

Ian sc, A “snifter” valve will only let in atm. air if the crankcase pressure is below air pressure, which for a non-pressurised motor it might well be.

[Ian S CParticipant @iansc]

Hi Gordon, I thought that was the case. The motor I’m working on Is being prepared for pressurization, I just need to fit a schrader valve and a pressure gauge. If I fit the side plate on the crank case as is, the motor drops revs and power(not a great amount). With pressure the motor will need to get rid of more heat, at the moment no external cooling is required. Ian S C
Mark I think you may just need a bigger flywheel, once the motor is run in you may get away with a smaller one,we’ll see!

Edited By Ian S C on 08/04/2010 11:06:11

[Mark Smith 3Participant @marksmith3]

Ian, I think the best place for the snifter valve is the top of one of the pistons to ensure quick delivery of pressure from the crankcase to the working cylinders, otherwise the engine will probably stop when you apply any pressure. That may be why your engine slowed down when you fitted the side plate as the piston is now compressing below it like a two stroke.

Can you PM me and print your email address so I can check it against what I have here.

Mark

[Ian S CParticipant @iansc]

You’r right about the snifter valve in the piston, but it will require one in the crankcase too I think, and it should equalise, unless the pistons fit too well, the best way would be to use a cup seal on the cold piston.
Going to have to make a tap to put in a thread for a pressure gauge, should be OK case hardened the fitting will be either brass or aluminium. The thread appears to be 8mm x .75. The gauge is a secondhand cheap Chinese.Ian S C

[Mark Smith 3Participant @marksmith3]

I have a cheap chinese set of taps and one of them is a taper tap that fits the pressure guage I happen to have just need ptfe tape to seal. Emails working fine now.

Mark

Edited By Mark Smith 3 on 10/04/2010 08:34:14

[Ian S CParticipant @iansc]

Just have to keep fingers crossed on the E-mail front.
What size is that tap of your’s, The 8mm x .75mm is much finer than the standard metric fine thread which is 1mm.just asking because if you have one, they must be available. Ian S C

[Clive1958Participant @clive1958]

Hi,

      yes i am still reading this thread, just thought i would mention 8mm x 0.75mm are definitely available as i have one that i acquired in my last job, it was used to tap a hole for water fittings on obara welding guns  which are of japanese origin, hope this helps.

 

Regards

Clive 

[Ian S CParticipant @iansc]

Hi Clive, it seems to be the same thread as the jets for my Primus torch. Called in at the local secondhand shop this morning, and found that they have got 7mm 9mm 10mm 11mm 12mm 14mm x.75, but from what I saw no 8mm, but i’ll have another look. I might buy a few of them as they are only $NZ4(at the moment about ?2).
Hi Mark had a great day out, must have been 20+ planes, and a similar no of cars(one Kombi).It was a bit breasy so no hot air engine run, but a hot air balloonhad a flight in the morning. Ian S C

[Mark Smith 3Participant @marksmith3]

Glad your day was good,  Ian. I am going to use the system Roy Darlington uses for cooler jackets, namely a tube slightly bigger in dia. than the cylinder and sealed at each end with O rings. I have a suitable tube, just need to get a box of O rings to find a suitable size that seals and is reasonably easy to assemble. 

Did you get my emails?

[Ian S CParticipant @iansc]

I’ll be able to make any hot air engine I like, just got an E-Mail from the world bank to say I’v got $US8,000,000-00 and all I need to do is send them $500,HA HA HA.
got e-mail, just replied.
I’v got some O-rings they’r about 1 1/2″. you have to be careful about heat on the O ring on the hot end of the water jacket on the hot cylinder,some types of O-ring become extremely toxic if over heated, as do some plastics.
My latest thoughts are that for a similar engine to the one I’v just built I’d tend to go air cooled,I have run it once with water cooling,and after 2hrs the water temp went up to about 35-40 deg C, I’ll just have to see if more cooling is needed under pressure. Ian S C

[Ian S CParticipant @iansc]

anyone got an idea, had the RossYoke engine running with the junior hacksaw(power hacksaw with junior blade), the engine runs up to 800-900rpm and runs for a few minutes, it then drops to 300-400rpm for about a minute before speeding up again. I will admit that it still is not completely run in and if I put some lubricant on the pistons it makes quite a difference to revs and power. It takes less than one and a half minutes to cut 1/2″x 1/8″ brass with a used blade.Ian S C

[Ian S CParticipant @iansc]

Never tried this before, Tonight I drove the Ross Yoke engine with one of my other engines to see what would happen. After running for 1/2 an hr I got the temperature down to -4.7 deg C, the ambiant temp at the time was 15 deg C, so an interesting experiment. The motor used for driving is the one in one of Marks’ photos, based on James G. Rizzo’s Dyna which was the second engine that I built back in 1994, this engine is much more powerful than it would appear to be from the book, And it managed to turn the other motor at a constant 500rpm.Ian S C

[Mark Smith 3Participant @marksmith3]

In Andy Ross’s book Stirling Engines he describes a demonstration that the Phillips engineers used to do. They connected a small stirling to a motor generator and motored the stirling with the electric motor until liquid air  formed around the hot cylinder. Then they disconnected the power unit and the motor ran the opposite way until the temperature equalised. Next they again coupled up the motor and  drove the engine in the opposite direction to normal until the hot end glowed red; from there under it’ own power, the engine behaved as a stirling until it cooled. Interesting that you drove one stirling with another.

Mark

[Ian S CParticipant @iansc]

Hi Mark, went and tried the Phillips expirement, 45min took the temp down to -7.1deg C, but thats not enough to run the motor although there was indication that there was something there, it would need to go quite a bit colder than that(might need an electric motor), I think -20 would be a target I could try for. On reversing the drive on the slave motor it took about 10 min to get to 40 deg C,it wouldn’t go any higher. I then ran the motor I’d been using as a driver without a load, the max speed I can easily read on my taco is 1500rpm,it was well over 2000rpm, and maybe nearer 3000rpm, and the peak rpm was a miniute after turning the gas off. The displacer started to vibrate, touching the cylinder sides, I don’t think it did any damage but it did scare me a bit, its never gone that fast before(the one in James G. Rizzo’s book did 320rpm). Ian S C

[Mark Smith 3Participant @marksmith3]

How do you explain that? What changed? By just using the “dyna” type motor as a driver of another engine and then you uncoupled it and it started perfoming as never before.That’s amazing.

It might have something to do with that peculiarity that these engine have of being difficult to get started but once they do start they generally get better and better.

Mark

[Gordon WParticipant @gordonw]

Might the improvement in performance be partly due to “running in”? Interesting motoring the engine and getting cold, of course we all know this is supposed to happen, but to experience it must be great. Slightly tongue in cheek question ; I’ve managed to explain to the lads down the pub how a hot air engine works, sort of, but totally failed to explain how they can run in reverse, any ideas?

[Ian S CParticipant @iansc]

I a wee bit puzzled myself, the engine is well run in, it had a rebuild after nearly 2000hrs, it was built in 1994 as my second hot air engine, and up to now has been my best engine. I must admit that I don’t usually let it run unloaded, I don’t think it’s good for its health. This motor started first flick and ran up to 200-300rpm, and going by the book I thought that was it. I fitted a generator to it after a few hrs running, and then started burning out light bulbs as it got more powerful. First light was 3v, the generator was putting out 1.5v, so I left it running over night, in the morningthe generator was putting out 6v-1st dead light, did in 2 more in the next few weeks. Ian S C

[Ian S CParticipant @iansc]

Hi all, I,v had the brake on the Ross yoke motor, and so far its best power is at 625rpm-4.9 watts, that seems OK, I must check my other motors again to compare them, its that long since I did any tests that I’v forgotten the results.Ian S C

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