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Hot air and stirling engines
| Mark Smith 3 | 17/10/2009 21:16:59 |
 175 forum posts 36 photos | Sounds like they are similar to stirlings in power output. Good to hear you got your LTD going, it seems quite large for one of these.
I tried to start my new motor but no go. I need to make the ratio of the piston volumn to the displacer volumn bigger, and the displacer was too loose a fit, but I haven't got a tube around of the correct diameter so have tried to split a light stainless tube from a vacuum cleaner and braze a section in. The trouble is I can't seem to braze it without burning the flux and leaving a black mess; tried four times. I have a lot to learn about brazing long lengths. I am going to try using my small forge to bring the job to red heat and introduce the flux and the rod at the same time that way the flame from my blow torch won't interfere with the flux. The torch doesn't seem hot enough and the flame is too broad. sometimes the rod melts then it won't - very frustrating
 . I look at people who build boilers and marvel at their skill, all those joints and not one leak! I'll let you know how I get on. We have a tig welder at work that can handle stainless and aluminium but the thicknesses have to be similar so my son tells me. If all else fails with the displacer I might climb down from my horse and get him to braze the joint with oxy acetylene. |
| Ian S C | 19/10/2009 06:32:52 |
 7468 forum posts 230 photos | Hi mark sound tho you have lpg for brazing like me,years ago I got a carbon arc torch for the stick welder,but I hav'nt had a great deal of success with that either,used to be able to go just a few doors down the road and borrow a mates oxy welder,but he died last year and I think he took it with him(we reccon he was going someware hot).the only welding/brazing I'v been taught was with gas in the RNZAF back in the mid 60s(did ok in the trade tests,think it was 92%).In that test we made a little fire shovel,the handle along sightly conical shape with a gas welded seam up its full length,think it was about 16 swg,some of the blokes had great fun blowing holes and getting distortion.Reccon with a bit of practice I could do 20 g with gas,but I'v seen that done easy with MIG.Looked at some MIG welders in Smith's City today(they'v got a sale)but they still look a bit above my price range.IAN S C |
| Mark Smith 3 | 19/10/2009 08:58:09 |
175 forum posts 36 photos | I have a gas torch but it is not hot enough. I have also got an old fashion kerosene blow torch like plumbers used to use. If I get everything right and prick the jet it can produce an intense heat but with a broad flame. On my fifth attempt to braze the long joint on the displacer I buried it deep in cat litter and packed refractory small pieces around it the brought it up to bright red heat, sprinkled flux and ran the rod along the joint; it worked. But I also pushed pieces of refractory material into the tube to keep the parts together. At my earlier attempts I had noticed the gap get wider as the heat was applied and the rod would not fill that gap. Displacer is now finished and ready to be installed. I had thought about using my forge but it was a bit windy on the weekend. Cat litter makes a good hearth material as it is made of part fired clay like bisque.
You could try Trade Me for a mig. They are not easy to use to start with. I learned on restoring my Kombi and I found that with panel steel short, well spaced tacks and gradually fill in the gaps seems best with the cheaper types. You can, however, weld half inch thick steel with ease but you need to make a couple of passes.
How rude of that chap to drop off and take his gas set with him you just can't explain insensitivity like that can you? |
| Ian S C | 19/10/2009 10:31:00 |
7468 forum posts 230 photos | The blowlamp I'v got is a petrol one,it blew back on me one day about 20yrs ago,and I drop kicked it out the door,then went and got the lpg kit,the old blowlamp was mums fathers,He was foreman plumber at Brown&Poulsons in Paisly Scotland.Got a friend who has a MIG,he's using it to rebuild a Jail Bar Ford van,before he got it he asked me what he should get,and I sugested he should get the biggest he could afford and that I really didn't know that much about MIG,he did just that(big wire reel included)$600 for a machine worth $3500,he uses co2 rather than argon.I must have a go with it,he finds it a dream to use on both pannel steel,and welding up the modifications on the chassis(the vehicle had been hotrodded),Mig would be a good skill for building our little engines,much less messy than stick,although that might improve if I got an electronic mask. |
| Ian S C | 21/10/2009 12:41:11 |
7468 forum posts 230 photos | Started collecting the bits for the next motor,I hope to build one with a ross yoke with a 35mm bore.Found what I think will make a good stainless hot cap,the stainless tube that is the support tube for an LED garden light,32mm dia 97mm long and .3mm wall thickness,I'll cut up another one to get the metal required for the hot end,and I'll make the piston from aluminium,I'll make the cold piston from cast iron if possible,that way I should get fairly near to ballance.I'v got 2 bits of stainless bar to carve out for the displacer cylinder.Now I'v got to work out what I need for a crankcase.I used to have some window weights 1 3/4"dia they had 18 cast on them maybe 18lb,the only ones I have are rough and about 1 1/2"dia and I want to use it to make cylinder liners with 35mm bore and also the power piston,so of hunting. |
| Gordon W | 21/10/2009 15:07:39 |
| 2011 forum posts | Hi ,'m still collecting parts for my new "big" model. Fly wheel- 2 brake discs, one with centre cut out, bolted together and to a flange. Some ideas on welding etc.. Stainless steel is easy to silver solder with correct flux, bad conducter of heat so prop. torch OK. MIG on thin stuff not easy, I do "plug welds" on the 2CV. Have just got some MIG brazing wire, use with argon, I'm still practising but looks good for thin stuff and S/St. N.B not for pressure vessels, before somebody shoots me down. |
| Mark Smith 3 | 22/10/2009 10:00:37 |
175 forum posts 36 photos | Ian, I don't envy you boring out all that material.
Gordon I like the idea of disc brakes for big flywheels, might look out for a couple.
I went into a second hand book store the other day and found a 1970 "Model Engineer" which isn't so interesting except that tucked inside was a 1950 Nov. 23rd ME that had a plan for a hot air engine - not the most sophisticated design but quite large and practical; it used part of a truck chassis as the frame! The article was by R.F.M. Woodforde, if that means anything to anyone. It is a gamma design, fired by town gas and did 250 RPM. (though he thought ity would do twice that if the piston han been "ground and polished". "The displacer chamber", as he terms it, was made from 3" cast iron down pipe, imagine that! This was turned thin with a carbide tool, because as he said the cast iron is "hard and sandy".
I pointed out to the chap selling the mags that there was another one inside he said that it was a bonus and ddin't charge me for it. |
| Ian S C | 22/10/2009 11:59:32 |
7468 forum posts 230 photos | Hi mark,wasn't Smiths by chance,I'v bought quite a few ME,and other books there,including a bound ME vol 1.The rim of one of my flywheels is from the sort of top hat bit on a large disc brake.I was woundering if I flanged the piece to go in the end of the displacer I might use that as an expirement with spot welding by making small overlapping spots,but I think brazing will be the way I go(I havn't built the spot welder yet)Gordon,I'v made quite a few flywheels by using 3 steel discs,the center one is bored to take a hub,and drilled for lightness or spokes cut.Then the other two are bored to the dia of the inside of the rim,all three then clamped up,and drilled and tapped and counter drilled for the heads of the cap screws,I usually use 6 screws,alternating from left to right,I'v got a supply of 160mm dia x 8mm discs.I'v made one 14" dia using 10mm plate,I used 12 1/4" unf cap screws on that one.Oh I forgot I finnish the outside of the rim is done after its all bolted together.Boring out the stainless isn't too bad,although I would prefer a bit more metal on the dia,bore out,put on to a mandril then turn down the outside. |
| Mark Smith 3 | 22/10/2009 19:13:28 |
175 forum posts 36 photos | No, not Smiths but the one in Selwyn St; but I might try Smiths as I am still looking for the article by Andy Ross in an ME from the early 1980s. Tried to see how to get back issues on this site but it isn't very clear how to go about it or I'm thick - mmm maybe that's it  . Going to the VW october Fest in Oamaru this weekend I am going to take my engine to amuse as it sports a couple of VW parts. |
| Gordon W | 23/10/2009 10:36:55 |
| 2011 forum posts | 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 C | 23/10/2009 11:29:27 |
7468 forum posts 230 photos | 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 3 | 28/10/2009 07:31:51 |
175 forum posts 36 photos | 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 C | 28/10/2009 12:30:40 |
7468 forum posts 230 photos | 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 3 | 01/11/2009 05:43:33 |
175 forum posts 36 photos | 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 3 | 01/11/2009 06:21:18 |
175 forum posts 36 photos | 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 C | 01/11/2009 11:33:15 |
7468 forum posts 230 photos | 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 C | 03/11/2009 08:32:39 |
7468 forum posts 230 photos | 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 C | 05/11/2009 10:06:09 |
7468 forum posts 230 photos | 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 C | 09/11/2009 10:05:50 |
7468 forum posts 230 photos | 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 3 | 09/11/2009 18:12:15 |
175 forum posts 36 photos | 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 |
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All Forum Topics > Beginners questions > Hot air and stirling engines