Hot air and stirling engines

[Gordon WParticipant @gordonw]

Hi, Ian- Flywheels, my problems are 1) can’t get much in way of material except scrap, can’t afford it anyway. 2) Lath will only turn 8″ dia. max. truing up usually done with my favourit tool, the angle grinder. Should be OK for low revs.

[Ian S CParticipant @iansc]

Gordon you’v just got to use what you can,my first large one is a hand wheel from an old sewing machine.Mark last time I was in Smiths they had Model Engineer mainly 50s & 60s,I bought up a little pile of them a few yrs ago.

[Mark Smith 3Participant @marksmith3]

Thanks Ian I will look at Smiths.

I have a tube of stainless steel that has a welded seam. I want to use it for my Beta pressurised engine. The bore is 35mm but the seam was a prob;lem as I didn’t want to bore it with a tool because of the tool marks that need to be honed out. How I solved the problem was to set it up true in the three jaw and the steady. Then I fitted a high speed air grinder on the tool post. After fifteen passes or there abouts and with the lathe running at max speed for this machine, the seam has gone leaving a near perfect surface that will just need a light honing to finish. I don’t know if good engineers would approve but it seems to have done the trick..

I will see you on Sunday, What time?

[Ian S CParticipant @iansc]

The tube sounds ok,I even do that with water pipe,although once after I had taken the weld ridge off the inside the pipe popped open and I had to clamp it up and weld it down the outside,its still in use as a power cylinder.The 35mm stainless tube i’v got needs an end fitted and a thread on the other end.Looks like a good forecast for Sunday,I want plenty of rain between now and then,give use water in the dam to run the turbine,we run it two or three times for about 5 miniuts a time depending on the water supply,It might only be about 8hp,but it uses water at a prodigious rate.Think the forecast is NW,at Homebush thats good,its sheltered from that,see you any time from 10am,I’ll probablly be there 9-9.30,got to oil the machinery,I was supposed to do it on tues but something else came up.Oh well theres a bit of sleet now,its been raining a few hrs,it must be bed time.IAN S C Hi circlip see your on tonight,yep Im wandering again!

Edited By Ian S C on 28/10/2009 12:38:31

[Mark Smith 3Participant @marksmith3]

Thanks Ian for  agreat day at Homebush. My grandson and I had a great day. My engine ran reliably all day as did yours. I was impressed with your engineering showing I have a long way to go. I was very impressed with the hacksaw driven from the large gas fired engine you built. I have come away with “ideas” and a renewed enthusiasim to complete my projects and start some others. I will put up a couple of pics of the day.

Edited By Mark Smith 3 on 01/11/2009 06:10:22

Edited By Mark Smith 3 on 01/11/2009 06:18:23

[Mark Smith 3Participant @marksmith3]

Sorry Ian I tried to upload a pic of your engine but it refuses to go in to the thread. Any one who wants to see it, have a look at my Home bush album

[Ian S CParticipant @iansc]

No worry,picture looks ok were it is,at that stage it was generating 6.45v and powering the fan behind the radiator,a radio,and one of the lights on the control panel(out of 8),later I had my little power hacksaw on it,but didn’t have the correct pullies,it didn’t get through the 1/2″dia steel bar for some reason,usually only takes 15-20 min,try again on the 15th.The turbine was installed in 1881,I think the order for it went out about 1878,it came from Dayton Ohio in USA,and comunication was by sailing ship,so if you wanted a reply tro a letter it would be 6 months or so,then after it got to NZ it would be brought the 50km from Christchurch by bullock waggon,today-send E-mail load into container,3wks at sea,on to truck at the port,an hour later its arrived,then again it would proberbly be built here anyway,and produce more than the estimated 8hp.Well our engines had a good run,and created a bit of interest,there is always someone curious,wanting to know how they work,occasionly i’v had people who know a lot more than I,Canterbury university is a center of study for hot air power,also in the past we’v had visits from some that work for Whisper Tech.IAN S C

[Ian S CParticipant @iansc]

Mark if you see this have a look at your E-mail,I’v tried sending a bit about the motors that were there on Sunday,your mail got through ok.IAN S C

[Ian S CParticipant @iansc]

Mark if you do come up to Homebush on the 15th I ‘ll be taking a vacuum/flame gulper up,I think I’ll leave the free piston motor at home because I need to redo the springs on the power piston,it seems to have found more power,and needs more restraint.It will be the motor in the drawing I gave you,its going well on meths,even better on gas meths combined,the meths stops the gas getting blown out.I ran it tonight in the dark,it was quite interesting watching the flame being exhausted.IAN S C

[Ian S CParticipant @iansc]

Hi folks,just in from the workshop,I’v just built a wooden mock up of a Ross Drive hot air motor,I’m not sure if I’v got the bellcrank dimentions correct,some diagrams it appears to be a equilateral triangle,My one is 60mm and 35/35,crankshaft 1/2″ throw,the piston stroke is 13/16″,seems ok by me,this is a model of the next design that I would like to make,I intend to make it with about a 35mm bore.IAN S C

[Mark Smith 3Participant @marksmith3]

I like that drive, when I finish this current engine I will attempt it. Speaking of my engine I have been boring out the displacer end of the cylinder without much success until I reduced the lathe speed to its lowest but not back gear, stoned the edges of the tool each pass and it worked. The displacer itself is cut from a vacuum cleaner tube which is stainless and very thin walled; I’ll bring a length for you when I come out on Sunday.

Mark

[Ian S CParticipant @iansc]

I’ll bring the wooden Ross linkage model,and one or two other bits and pieces.I think I can fit the new engine into a space of about 6 1/2″(165mm)x 5″(130mm)x2″(50mm),and I think it would be easy enough to pressurise the motor.The way I make hot caps,I take a piece of steel the dia of the flange at the cold end,and a wee bit longer than final length,place in chuck,drill to depth as near to size as I have a drill,bore to size and square the bottom inside.On my hot caps the cold end has a thread cut internally to screw onto the cold end(I use 32 tpi on all my engines),then remove from the chuck.Mount up a steel bar and make a mandrel that includes a threaded part,drill a hole through the center(to let the air out),without removing the mandrel from the lathe place the bored out hot cap on the mandrel and turn the outer dia to size-whether this is the correct way or not I don’t know,but it works for me,when you teach yourself–well!IAN S C

[Mark Smith 3Participant @marksmith3]

Happy to report that my pressurised engine is now running – not  very well or fast but running. There is still a slight tight spot and the displacer is scraping along the cylinder. I will correct these problems before adding pressure in stages.

Has anyone knowledge of injecting live superheated steam into the compressed air in  the cylinder, it strikes me that it could be a way to introduce several hundred degrees of temperature and quantity of heat directly into the working medium plus the expansive properties of the steam itself. Interesting idea or waffle?

Mark

[Ian S CParticipant @iansc]

Hi Mark,that vacuum cleaner tube might work on my new engine,it gives me just over 2mm clearance over the stainless tube from the garden lights that I want to use for the hot cap.This evening I flanged over a disc of stainless to fit in the end of the vacuum cleaner tube,I want to get it TIG welded,the tube and end piece are about .5mm thick do you think this would weld OK?Sunday at homebush we had 510 people through over twice the number of the first weekend,thought it was a bit busier,at least there was quite a bit of interest in our engines.Good hear that the pressurised engine is running,shouldn’t be too difficult to sort out.Can’t help with your steam idea,maybe waffle don’t know.IAN S C

[Ian S CParticipant @iansc]

Hi Mark,got an end welded into the vacuum cleaner tube this afternoon,we’v got a stainles fabricator(Four Star Sheetmetal ltd)the boss is a wiz with the TIG,I also had a word with another of our local engineers,Chris Charles,brother of a certain LH golfer(Bob),he’s got a little hot air engine with a parabolic reflector.He was into things with a bit more than hot air engines,ie McLaren formular 1 motor racing,his hobby now is building racing Minnis.I took the tube in to ask him if I had the right set up,I was’nt sure if .5mm was weldable,thought I’d ask him so I didn’t make a joe of myself when I went to the welder,thier workshops are almost next to one another.IAN S C If the hot cap does’nt go together the way I want I found something else to use,the case from a D size Ni Cad battery is almost identical in dia to the tube from the garden light although maybe a little heavyer.

Edited By Ian S C on 18/11/2009 11:37:34

[Mark Smith 3Participant @marksmith3]

Good stuff,Ian. My engine is being stubborn at the moment but I will prevail I hope. Garden lights are about  $19 at the warehouse might be worth getting one.

Edited By Mark Smith 3 on 20/11/2009 09:50:14

[Ian S CParticipant @iansc]

Got my light out of the rubbish.The hot cap is in the citric acid,I think it needs reheating,think I missed a bit.Found something interesting,I was running the vacuum engine today,while making a wind gaurd,and found that if I placed a piece of sheet metal about 30mm directly behind the intake/exhaust hole the speed almost doubled-move it back and the speed drops off,perhaps the hot air from the exhaust is being recycled-supercharged vacuum engine.If the weather looks OK in the morning I’ll go down to Kirwee to the A&P show some of the vintage machinery blokes will be there.If theres too much NW wind forecast for the afternoon I won’t bother,10k on the bike into that aint worth it.I’v got the trailer on the bike and packed the little Tapper type engine and the Vacuum engine.Last year took the large engine(dyna)and gas bottle.

[CirclipParticipant @circlip]

Nurture the Tig specialist Ian.

 

  When trying to make another type of hot air “Engine” (a “Brauner design pulse-jet) I got my most experianced tigger to weld the longitudinal seam on a rolled up piece of 321 sheet. It still came out with a banana bend in it that no amount of planishing would remove.

 

  Stainless garden light stems? almost makes me think of having another go, flamin Chinese.

 

  And as a noted “Recycler” you know that Tig electrodes make super scribers and bits fastened into an appropriate holder are good for  groove turning and slotting tools??

 

  Regards  Ian.

Edited By Circlip on 20/11/2009 12:40:17

[Ian S CParticipant @iansc]

THanks for the tips on TIG electrodes(got one),The sections of garden light stem are nigh perfect size for a displacer ie 30mm dia x 97 long,nominal three to one ratio is about right,and if you use the extra 7mm thats OK,and they are about .oo5″ thick.I immagine that there is quiet an art in welding a seam like the one you got done.I imagine it was thinner steel than off the shelf stuff,did you get the engine running?Mark,I went down to the show today and joined up with the vintage machinery group,they had a dozen engines there.The wind was rather frisky,but I got the little tapper going,there was plenty of interest in it,and I used 200ml of meths.Quite a bit of machinery there including two traction engines.IAN S C

[Mark Smith 3Participant @marksmith3]

I feel guilty should have gone to that, need to look at the calendar of events a bit more. As Circlip says look after that tig guy, I am i bit lucky my son who works with me is a superb tigger and I get it done for free.

Did you guys ever wonder about the anomaly between dead space and moving regenerators such as Robinson motors and experiments done by David Urwick who used wire gauze regenerators? These regenerators must introduce massive dead space. According to ancient wisdom they shouldn’t work at all should they? Or is there something we’re missing.

[Ian S CParticipant @iansc]

Hi mark,was at $2 shop south city,found a cylindrical thing with a flower in it and a candle on top,the main body is clear plastic,but the bottom is a thin walled stainless steel cylinder 31/32″dia 50mm x 3 7/8″ long 100mm,it has a bottom but I think itts just pressed in-$3 bought one now to see if I’v got a use for it.Must look up the artical on dead space,its in one of my older copies.Theres also the laminar flow engine to think of.I seem to remember reading somewear about this question.Are you looking for welding rods,The Tool Shed in Montreal st has 5kg packs of 2mm rods for $9.50(usualy$48),when I head off home with my sister Anne tomorrow I’m going to pick up 2 packs.While I was in there today I got new bandsaw blades,sick of brazing the old ones,and I’m cutting up some scrap to make he crankcase for the new engine.I,m going to try attaching the hot cap to its flange with loktite.

[Mark Smith 3Participant @marksmith3]

With regard to piston/displacer engines, nothing demonstrates that these small engines operate above and below atmospheric than when you remove the flywheel, give the shaft a flick and it runs at amazing speed – all be it with very little torque. I did this with my grandson’s engine just to see what would happen as you did with yours, Ian. But this is not the case with high tech engines that are sealed from the atmosphere; they must operate on variations of positive pressure.

 

I am keen to investigate the dead space issue because, if you look at the Robinson engine with its huge dead space between the power cylinder and the working cylinder then couple that with the relatively empty space in the moving regenerator it should not work according to common wisdom, but it does and quite successfully by all accounts. In the case of this engine maybe the displacer is less a regenerator and more a heat transfer device – there is a difference here. What I am thinking is that when the displacer is in the top of its cylinder the regenerative material absorbs heat and then on descending,dumps that heat into the incoming cool air which, once heated does work by expanding and therefore cooling while pushing on the cool air in the working cylinder. Maybe there are three layers of  working air:  

 

That which is hot all the time,

 

A middle third that absorbs and dumps heat

 

And the third that is just a cool medium that pushes the piston out.

 

So, according to this logic, it is only the middle third that is effected by temperature changes. I suspect the same is true for standard displacer engines.

 

Looking at the very successful Phillips “Model ten engine”, it has a seal at the bottom of the displacer that forces the air out and down the external heat exchangers and regenerator. When you think about it, the air is heated twice: incoming and outgoing which is a waste of energy, whereas if you consider the Rider with the air transfer between the working piston extension and the piston itself, it is only heated once. Also in a Beta or Gamma design there is only about a third of the piston travel that is felt by the expanded air but in the rider, both pistons feel that pressure and so the ratio is doubled; so it is not surprising that a Rider is more powerful, as demonstrated by Andy Ross with his 35 cc engine that developed 44 watts unpressurised according to legend. Most usual displacer/piston engines can manage just 3 to 5 watts of the same capacity. I think we have a lot to learn about these incredibles machines, many secrets have yet to reveal themselves.

Edited By Mark Smith 3 on 23/11/2009 10:29:04

[MikeParticipant @mike89748]

You guys are always looking for sources of stainless steel tube – preferably free! Well, the other day my stainless steel thermos flask finally gave up the ghost after 30 years so, out of curiosity, I sawed the bottom off. This leaves me with a length of stainless tube 160mm long, 96mm in diameter, and with a wall thickness of approx 1.1mm. The internal vessel (the bit that holds the coffee) is about 10mm less in diameter, and has a domed end. Don’t know any more details because I haven’t got around to sawing the neck off yet.

If you do find such a flask, be careful when you attack it with a hacksaw. It contains insulating material in the form of a fine, black powder which I believe to be either carbon or graphite.

Thought this might be a bit of useful info…

[CirclipParticipant @circlip]

Having a “Home Tigger” is CHEATING ( Lucky S*d), No Ian the project was shelved due to the Banana. Pulse jets are red hot within seconds of starting and having a localised hot spot due to the shape of the tailpipe (Aforesaid Banana) would have been pushing safety a bit TOO far, b*gger off  Stan ‘n’ Ollie.

 

  Besides, Pulse jets were Illegal over here at the time    

[Ian S CParticipant @iansc]

Circlip you could have had fun with an aeroplane flying in circles(control line without the control lines)it would proberblyfly in ever deminishing circles until it disapeared up its own tail pipe.Teres a bloke here in NZ who has made them quite large,thinks they could power a cheap cruise missile,I think there is a site that shows a jet powered go-cart.Found another stainless container today at an Indian food shop at south city mall,I think it will be just right for a new hot end for my 2 1/4″ bore motor,the old mild steel hot end has got a great bulge in the end ie the bottom.Cost $3 99.Mike graphite is carbon.Did your thermos not have a glass vacuum flask inside the stainless outer casing?Mark I think it will make little difference running pressurised or unpressurised running without flywheel because there is the same ratio of pressure above and below the piston.

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