Hot air and stirling engines

[Mark Smith 3Participant @marksmith3]

That’s a good result for such a small motor, It’s going to be interesting to see how it performs with a bit of pressure.

I’ve got mine in bits again, It was running well except the bearing on the yoke which came from a line trimmer gudgen pin caused it to wobble under load so I changed it and guess what, no go. Never mind just had to push on and find the cause.

Mark

[Ian S CParticipant @iansc]

I imagine your bearing is a needle roller, about 10mm dia, I used a 6mm needle roller direct on the crank pin, the big end bearings have a 4mm bore, and came out of some electronic equipment as did the main bearings that are 8mm, havn’t managed to stuff them up yet, time will tell.
you only need a slight misalignment/realignment and you have to start all over to get things going, it’s not so bad as first time because you know that it did go. Thats the reason I don’t do a lot of painting on my motors, just the bits I don’t need to pull to bits, although this one hase been in bits a few times,I just have problems lineing up the cylinder head on the hot end, I should have made it more positively located. Ian S C

[Mark Smith 3Participant @marksmith3]

Well, it’s going again, and all I did on reassembly was change the oil to light sewing machine oil; a little heat and wrapped the wet undies for a cooler and away she went. This type of crank, namely a bell crank and a rocker arm give near perfect staight lines to the piston and displacer and not too difficult to build. Now to build the heater, cooler and the engine mounting.

Incidently I put two hard drive magnets that are kidney shaped on the flywheel for balance. I found the best setting was not `absolutely opposite the crank pin but a few degree ahead of it. I will post a pic of it at this stage but remember I am not an engineer and my engines are made of mostly found materials and junk parts, Ala rizzo.

Mark

[Mark Smith 3Participant @marksmith3]

Here it is, in the raw complete with wet undies. The mechanism is a bit hard to explain without pictures in case someone wants to try this crank drive for themselves.

The main advantage is the very low side loads on the con rods.

As you can see the bell crank was originally a Ross yoke for a Rider type engine but for various unknown reasons not to do with the crank it refused to run so I went back to the Beta design and changed it to what you see, and it works.

 

Edited By Mark Smith 3 on 15/05/2010 22:17:13

Edited By Mark Smith 3 on 15/05/2010 22:20:06

[Ian S CParticipant @iansc]

Hi Mark, have you tried holding a coil of wire near the magnets with a meter set on AC volts, with a fiddle around with various coils you might be supprised with the voltage, could be the start of a built in alternator. About the motor, if the frame next to the flywheel is made of steel the magnets could put quite a drag on the motor, I found that with the linear alternator on the Alpha (and before that Gamma)free piston engine. If it’s made of non-magnetic material its OK.
Found one way of running my LTD motor, at lunch time when cooking the veggies, i can sit it on the pot in place of the lid, that really gets it going!
Been reading through some of my old ME mags, and been looking at Andy Ross’s 1981 three part artical Rider stirling 35cc Engine, might just copy it,theres 12 pages, so with my lightening fast gear it will take all afternoon at least, but then it takes longer finding these things in my well organised library(not). Ian S C

[Mark Smith 3Participant @marksmith3]

The frame is aluminium so no problem there. You have already made a copy of those articles, Ian, I have them here. That is if you are talking about the 35cc rider. My engine ran for two hours then suddenlt stoped I think it probably overheated and changed the piston seal, but at least I know it  is a runner.

Mark

[Ian S CParticipant @iansc]

Oh well, I thought after I had started that I may have done them before, never mind I’v got a copy(2copies) also.
Yep you proberbly fried the cup seal, got to keep your knickers wet!
Did some work on my large version of tapper, new bearings, the old ones got nicked for the Ross Yoke engine. The Ringbom engine is going better than it has ever done, the torque was 5 1/2″ oz, but I did’nt take the revs, but they would be about 600rpm which by my calculations =2.4W which is great ’cause up to now it has’nt had enough power to even attempt to test it. Ian S C

[Ian S CParticipant @iansc]

Oh well I’v made some work for myself, Mark you may remember that free piston engine of mine that did’nt work too well at Homebush,got it up and going over the last few days, with a radio attached to it I got the voltage up to 4.25v, and the current to 13ma. Then I lost power so I’ll have to strip it and see whats happened. I suppose if you don’t break it your not trying hard enough. I worked out(might be wrong)the power as .5525watts thats twice as much as its ever done in the past. The power is generated by 2 magnets from a microwave oven, and the stator is 4 little transformers with the ‘I’s removed and the ‘E’s all turnedthe same way, and the secondarieswired in series and fed into a bridge rectifier.Perhaps I should put water in the cooling system! Ian S C

[Mark Smith 3Participant @marksmith3]

Sounds serious, Ian. I have overheated mine too, and it refuses to run now; as you say I have probably fried the seal. I might make a new one today and try again. The bell crank and rocker does work well and just need better engineering to improve it.

Mark

[Ian S CParticipant @iansc]

Found the problem, Took the displacer apart, and found that the displacer piston had collapsed. It was an aluminium aerosol can, I found another one and did the repair, and got it running in about an hour, but I,m now working on the radiator, some of the solder joints are leaking. At least I,v got my emergency radio back. One thing I did notice was that it now starts a lot faster, perhaps the piston has been slowly collapsing over quite some time, this is the first time in about10yrsthat I,v opened the displacer cylinder. The stainless that you gave me for the hot end of the Ross Yoke engine is exactly the right size, but as the cylinder is plain steel, putting a stainless piston inside I thought was a waste of materials.Ian S C

[Mark Smith 3Participant @marksmith3]

Can anyone throw light on this old engine, it seems to have been made from a set of castings probably maybe fifty or more years ago.

Mark

Edited By Mark Smith 3 on 22/06/2010 06:49:11

[Ian S CParticipant @iansc]

Mark, it looks interesting,did you get my e-mail the other day, my computer died about the that time.I sent you an address of someone who might know a bit about it. Be good when I get back on my own machine, but I’m getting some gardening done instead.Ian S C

[Mark Smith 3Participant @marksmith3]

Hi Ian,

I did get an email but there was no message, not sure what happened there.

I was going to take the boys to Mc Lean’s Island to the steam society for a crank up with the vintage machinery club but the weather going to put a stop to that, shame, they have been asking when we go again to run their hot air engines for a crowd. Maybe the weather people will be wrong, we can only hope. 

A friend has the engine above and he has been trying to get it running better, but since he started he has only made it worse; I fear he is going to damage it before he hands it on to me to fix. The main problem that could see was it leaks air at the flanges – no gaskets just gasket goo. There is no friction and it might leak back past the piston which is not a big deal so long it is at a minimum.

I did get it to run when he first brought it around but it took 5 minutes of gas  flame before it started and was ant power. Also it has no cooling system and the heat transfered to the cold cylinder very quickly – maybe some wet undies might help here in the interim, what think ye? This engine should easily run with meths or a mamod tablet.

As for your computer, now I understand why I got no replies. Thought I was in the dog box maybe.

Mark

[Ian S CParticipant @iansc]

You’r not in the ‘dog box’,your mate might be. Its nice and warm in the steam hall at McLeans Island but I don’t suppose they’d let you run things in there.

my computor suffered from a hot air problem, the fan on the power supply seized up, and the the power supply died.

That engine was proberbly made to run on meths. You could add fins, or make a water jacket to slide over the top bit of the displacer cylinder.

What is the little bit sticking out the side at the bottom of the power cylinder?

Think I sent a message on here, have a look.Ian S C

[Mark Smith 3Participant @marksmith3]

The little bit you see is a long allen screw that is supposed to block the end of the transfer tube. I don’t think it was like that originally.  The transfer tube is screwed into the displacer via a brazed boss which is threaded internally. I suspect that is another source of leakage which teflon tape should cure. But the greatest leak seems to be between the flanges below the power piston. A gasket should cure that.

The displacer rod is large for such a small engine 3/16″. Also the gap around the displacer and its cylinder is large, too. I estimate nearly 1/16″; too big according to Rizzo. But the engine does run with enough heat.

Mark

[Ian S CParticipant @iansc]

Hi Mark,I’v got the old windows’95 computor going. Thought the fitting on the power cylinder was either a snifter valve or a bleed to control engine speed. The displacer rod looks more like 5/16″ from what I can see, 3/16″ wouldn’t be too big, I,v used that myself-usually stainless tube. 1/16″ shouldn’t be too bad for the gap. The con-rod on the power piston looks rather solid, that could do with lightening. What bearings has it got, plain or ball? Ian S C

Edited By Ian S C on 26/06/2010 14:54:18

[Mark Smith 3Participant @marksmith3]

They are plain bearings, Ian. Good to see you are back on line. Windows 95, wow, vintage!

Mark

[Ian S CParticipant @iansc]

Yep we’r getting there, hope for an up date soon, this one could just about go to the museum. Is there any room to bore out the old , and fit ball races, even if you’v got to go down a little on shaft size, although a good fitting plain bearing with light lubrication, maybe 3 in 1 oil is not too bad. Ian S C ps don’t know if I can get through on e-mail, I,ll keep trying.

[Mark Smith 3Participant @marksmith3]

There is probably not enough room for ball races, but the plain bearing are free running anyway.

Mark 

[Ian S CParticipant @iansc]

Thats OK, they look as if they are brass or bronze, and if oiled they will be good, and I suppose it should be kept original.
I missed a copy of ME so I sent off for it, and it arrived today(no., 4375), its got a very interesting artical by Ted Pepper, A Look Inside The Stirling Engine, he’s gone a bit more high tech than we have with instruments for pressure testing the engine while it runs, but comes to the same conclusions I have, worth a read. Ian S C

[Ian S CParticipant @iansc]

Here we go again, I’v wrecked the 3rd displacer on the free piston motor, 2nd in 6 wks, I’v replaced it with one made of stainless steel, the aluminium deodorant aerosol cans just don’t stand the heat, they are OK for light duty demo engines.
We can give your motor a name, its basicly a Heinrici type, Theres one similar size in James G. Rizzo’s book “The Stirling Engine Manual” with fins around the top of the displacer cylinder.Ian S C

[Ian S CParticipant @iansc]

Hi all I’m trying to load some photos of my Ross Yoke Engine into an album just to give you some idea what can be built out of junk.Ian S C

[Ian S CParticipant @iansc]

I’v done it! I got some picture

s in an album.

[Gordon WParticipant @gordonw]

Wish I had scrap like that. Whats the rusty bit on top, gas burner? My “big ” motor not coming along very well, due to summer, and having to fix house, garden, car etc. Roll on winter.

[Mark Smith 3Participant @marksmith3]

I never thought I would hear someone yearn for winter, Gordon. I can attest that Ians engine runs very well.

Mark

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