Hot air and stirling engines

[Trumpet / FlugelParticipant @trumpetflugel]

May I suggest trumpet valve oil as a lubricant? Ready available at most musical instrument shops, a bottle will cost around a fiver. It’s a bit like sewing machine oil but perhaps a bit less viscose.

 

Hope this is of interest.

 

Peter.

[Rob StevensParticipant @robstevens54297]

Gun oil or air tool oil might be possibilities.

 

Rob

[Donhe7Participant @donhe7]

I was told during my teens, (by “oldtimers”) that “kerosene is abrasive, whilst distillate is a lubricant”, a prime example is in the Deisel fuel injection pump, which relies solely on the “deisolene”, “distillate”, (in other words, the non-volatile fuel, sold to power the tractors and trucks in the paddocks and on roads under various brands and names), so if you are able to source this product, it should serve to lubricate a Stirling engine, relatively cheaply

 

donhe7

[Ian S CParticipant @iansc]

Kerosene, or parafin used to come in a number of grades, ie., power kero, or TVO tractor vaporizing oil, and lighting oil, for use in lamps. It is obtained in the same process of distillation as petrol/ gasolene. To run a vehicle on TVO, a petrol tank is required for starting, once the engine has warmed up, the TVO tap is turned on, closing the petrol supply, if you do this before the engine is warm enough there will be a great cloud of white smoke from the exhaust. Power kero was made up untiljet engines needed a higher powered fuel, they then made Avtur, or Jet A1.  The octane rating of power kero is about 50 – 65,  I seem to remember the petrol here back in the 1950s was 72 octane, although I see that war time petrol in UK was 78.  so thats where kero comes from.  Its a bit better as a lubricant than petrol.   Ian S C

Edited By Ian S C on 19/05/2011 13:07:41

[Donhe7Participant @donhe7]

Posted by Ian S C on 19/05/2011 12:48:55:

Kerosene, or parafin used to come in a number of grades, ie., power kero, or TVO tractor vaporizing oil, and lighting oil, for use in lamps. It is obtained in the same process of distillation as petrol/ gasolene. To run a vehicle on TVO, a petrol tank is required for starting, once the engine has warmed up, the TVO tap is turned on, closing the petrol supply, if you do this before the engine is warm enough there will be a great cloud of white smoke from the exhaust. Power kero was made up untiljet engines needed a higher powered fuel, they then made Avtur, or Jet A1. The octane rating of power kero is about 50 – 65, I seem to remember the petrol here back in the 1950s was 72 octane, although I see that war time petrol in UK was 78. so thats where kero comes from. Its a bit better as a lubricant than petrol. Ian S C

Edited By Ian S C on 19/05/2011 13:07:41

You’re talking (Writing) to someone who spent a few years sitting on a tractor which ran on “power kero”, with exactly that system, (an old 1948 Fordson), and am very familiar with the vagaries of the beast.

The one which I was driving had a habit of dripping un-vaporised fuel onto the hot manifold, and then blowing the fumes back over the driver, (no cabins or air conditioning in those days), not a most enjoyable experience!!

Another result of running these engines too cold was the fact that if run too long , too cold, the crankcase could fill up with a mixture of raw fuel and lubricating oil, which did result in another make of tractor stopping, when the mix started to run into the magneto.

Upon draining the crankcase 14 GALLONS of mix were found!!!

All very(historically) amusing, but just a little(!) off thread, I know, but these memories are called to mind when power kero (vapourising oil to the Brits), is mentioned, sorry,

 

donhe7

[Gordon WParticipant @gordonw]

A bit of advice from you old timers, please. My large model, horizontal, engine is drawing closer to finished, one big problem is the displacer piston is too heavy and binds on the tailshaft bushes. It’s about 4″ dia. and 8″ long, made from stainless steel 0.8 mm thick (the best I could get) it’s way to out of round to skim down. Now my idea is to put a bearing in a pocket under the cylinder, just enough to take some strain, as done in some full size engines. Question what would be best, expect temps up to red heat, dirty and oily (not me) Thinking brass wheel on stainless pin, or stainless ball race, any ideas?

[Ian S CParticipant @iansc]

Hi Gordon, apart from the horizontal arrangment of your motorI don’t know much about it, so I’ll say how I might do it. One; keep away from bits rattling around inside the motor.I would drive the displacer with a Scotch drive, and extend the rod past the crankshaft, and into a linear bearing teflon would be good here, but bronze/ brass or cast iron would also work well.

Most of my motors are vertical for this very reason, with a bit of luck gravity keeps things fairly straight. Then it’s just a case of deciding which way up, hot at bottom, easy heating, but the heat rises, usually no problem. Hot end on top, a bit of design work needed for a burner, OK with gas, but NBG for other fuels. Horizontal, a bit more friction on the displacer shaft, but my 2nd and oldest surviving motor(1994) is a vertion of James G. Rizzo’s Dyna, and in its early years ran 2000 hrs until it wore out the bearings, both con rods and the crankshaft. That motor drives a hacksaw with a junior size blade, and that cut the metal for the new parts (slowly). New bits bigger bearings, and proberbly 100 hrssince overhaul, it will last for ever.

Fot high temperatures I’v heard of ceramic bearings, but know nothing of them.

Ian S C

[Gordon WParticipant @gordonw]

Ian, thanks for reply, afraid I didn’t explain very well. My motor (will be) a sort of generic copy of the sort of thing sold in the heyday of hot air engines. I just don’t like the thought of all that heat rising up, and heating the cooling water, just me. The displacer tail shaft is supported by two bushes, one at the displacer, one about5″ behind, shaft will be moved by a sort of trunnion affair, pushing the shaft, in theory should be no sideways load, bushes are brass at the moment with ptfe gland. main prob. is the weight of the displacer, which is why I thought of a support under the displacer. Two alternatives are finding some new material for the displacer, lightweight heatproof foam ?,or change the whole thing to a vertical cyl. ( I’ve seen the pic. of yours with the gas heater). I’m about to start on the final steel base-plate for this so need to make a decision soon.

[Keith LongParticipant @keithlong89920]

Gordon

For a lightweight heatproof foam you could try using Celotex. You can probably cadge an off-cut from a builders merchants or a builder who does work involving insulation. I tried it out with burning petrol on it when I was looking for some impact absorbing material for possible use in a racing car. Changed size a bit but kept all its structural integrity. Might vary from grade to grade but worth a look.

Keith

[Ian S CParticipant @iansc]

My horizontal motor was built before I knew about Scotch yokes, so the only bearing the displacer has is the 1 inch long X 1/4″ diameter teflon bush through the power piston. The only troble the teflon has caused was when I reassembled the motor after the over haul. I had got oil on the bush and it swelled, and I had to ream it out, it seems funny that a bearing can get tighter as it ages.

I think for a larger motor, vertical is best, I have one with a 2 1/4″ bore, and a 1 1/4″ power stroke. Its hot end is mild steel, and just about done for, I hav’nt run it for a year or two. I must get it out one day and take some photos. It is heated with a camp stove burner, and although the hot end has had too much heat, the cooling system keeps good care of the cold end.

Am I right assumming that your motor has two cylinders, one power, and the other the displacer? Ian S C

[Gordon WParticipant @gordonw]

Ian ,yes 2 cylinders, both horizontal. power cyl. is 74mm bore, displacer is 4″ bore. Won’t apologise for mixed dimns. because that’s what they are. Just bought my first digital camera, but wife is off to usa with it. On return will try to make it work and take some pics, then try to download (upload?). Keith, Celotex ? I don’t know this but will try to find some imfo. Sounds like it might be useful , PS I live in Scotland , nothing is cadgeable.

[Keith LongParticipant @keithlong89920]

Hi Gordon

Well if you live in Scotland the builders up there will certainly know about it. Its the yellow insulation board that you see in the diy sheds about £25 for a 2inch thick 8×4 sheet. Usually has ali foil stuck to one side at least. Don’t use the white stuff thats expanded polystyrene, definitely won’t withstand heat. Your best bet might be to keep a weather eye open when you’re passing anywhere that building is going on and there’s a skip parked there. With a bit of luck you could get your off cut that way. It’s worth asking in a builders merchants, the boards are fairly brittle so chunks do get broken off, especially if the fork lift driver is a bit ham fisted.

Keith

[Gordon WParticipant @gordonw]

Keith, if it’s the same stuff as kingspan I have some bits, don’t think it will take the heat but will do tests tomorrow, also have a couple of other ideas which might work. (wife’s away, one of the ideas involves a coffee grinder and microwave). Will report if any good.

[Mark Smith 3Participant @marksmith3]

I have made several engines now most have been horizontal engines. If the displacer is light enough, as it should be, there is no need to place rollers or bearings to support it.. The bailey Engine which had such rollers was a very large engine and could justify such a modification; model engines, on the other hand, do not need it as the shaft of the displacer, if 3/66″, should support the displacer without problems.

Mark

Edited By Mark Smith 3 on 27/06/2011 09:46:37

[Gordon WParticipant @gordonw]

Hello Mark, quite agree shouldn’t need any extra support, but displacer is over heavy, and binds on the bushes. Hence trying to discover lighter materials. my displacer is so far out of round can’t be skimmed thinner, anyway don’t think it would be strong enough. I’m new to this stuff (model making) was quite chuffed with the displacer when it was made.

[Ian S CParticipant @iansc]

Gordon, if your tube for the displacer is still open at both ends, is it possible to force something round through the bore, and if its long enough, and if you put a center in each end you should be able to skim it down quite a way, .015″ to .020″ would be OK, If you can, cut a disc of the same material and get soeone to TIG it in for the hot end, use aluminium for the cold end, high temp glue will hold that in place. Ian S C

[Ian S CParticipant @iansc]

This little motor is based on one built by Justin Jones in 1997, it featured in ME in March that year. It has a bore of .625″ bore and .5″ stroke on the power cylinder, and a stroke of .75″, and bore of .625″ for the displacer. It has a meths burner. It runs a little generator that supplies enough power for a 3 V radio. the capacity of the motor is somewhere about 2.5 cc. This is my 6th motor, and smallest.

Justin’s one was winner in the Gnat power competion. Ian S C

[Mark Smith 3Participant @marksmith3]

Hi Ian that is an interesting motor you have there, bell crank displacer drive I assume from the pic. I haven’t built anything since the quake just couldn’t get interested, but I have begun assembling tubes and other bits for a project that is a Beta design using half a Ross yoke. You just have to extend the rocker arm to match the top of the Ross yoke to drive either the displacer or the piston. I hope to come out for a visit maybe in the spring when things warm up and the earthquakes slow down a bit.

Mark

[Ian S CParticipant @iansc]

Hi Mark, you might be able to get out to the Homebush open days, last years ones went well, the stables were damaged in the September earthquake, but by November were repaired and heavily reinforced. First weekend the house was a pile of rubble, and by the next weekend the rubble was cleared and the ground smoothed. When the worst happens, you just have to get up and get going.

There is two versions of the little motor in ME back in ’98 GAMA , and BETTA, I desided that the GAMA would be the most efficient, with the piston so small the area of the rod going through would be noticable,(also fiddly). The gland for the displacer rod is a carbon impregnated teflon bush (theres a bit in my photo album about that). The bottom bearing for the bell crank is the ball bearing pivot from the tone arm of a record player. The original displacer was the body of a white board marker, the new oneis the shell of a AA size Ni Cad battery, its a bit too heavy, itr needs to be made of .005″ to .o10″ stainless steel. Ian S C

[Engine BuilderParticipant @enginebuilder]

I love this website

Edited By Engine Builder on 02/02/2012 20:24:35

Edited By Engine Builder on 02/02/2012 20:25:49

Edited By Engine Builder on 02/02/2012 20:26:19

[TerrydParticipant @terryd72465]

Posted by Engine Builder on 02/02/2012 20:22:56

I love this website

Hi Engine Builder,

 

I sympathise about this forum, it’s only the interesting and knowledgeable characters that keep me coming here. There are no instructions on how to use it, it’s all suck it and see. I’ve suggested a ‘How To…’ sticky thread but there appears to be no-one listening.

 

To embed a YouTube video:- when copying the embed code from YouTube, click on ‘Share’ beneath the video. Then on ‘Embed’, which I am sure that you have done already, but then select ‘Use old embed code’ on the list at the bottom. This brings up a new code which you can copy and embed here using the ‘YouTube’ insert button on the posting box.

 

At least I think that works! I’ll try below to show a rather nice engine, cross fingers, hold breath (but not for too long) and embed:

 

Stirling Engine

 

Best regards

Terry

Edited By Terryd on 03/02/2012 05:43:27

[Ian S CParticipant @iansc]

A nice looking engine from a collection of rather nice looking engines. Good use of the Ross Yoke. Is that glass that you are using for the base, looks good. Ian S C

[Engine BuilderParticipant @enginebuilder]

Thanks Terry I have followed your instructions, lets see if it works.

Hurray!

If anyone wants the plans for this simple engine please send my an email, address is on the video.

 

Edited By Engine Builder on 03/02/2012 11:18:08

[Ian S CParticipant @iansc]

This is my largest motor, a BETA type with a bore of 2 1/4" and a power stroke of 1 1/4" and adisplacer stroke of 1 3/4". I have not tested its power since I fitted a new stainless steel displacer cylinder, the old cylinder was mild steel, and had bulges in it, and the inside was flaking. Ian S C

Edited By Ian S C on 23/07/2012 15:45:53

[HopperParticipant @hopper]

Anyone know what happened to stirlingengineforum.com the last couple of days?

It seems to no longer exist and the link on the "site no longer available" page leads to nothing.

Would be a shame for it to disappear, there was a wealth of information on that site.

[Author]

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