Stirling Engine Fan

Good evening,

This afternoon I have been trying to sort out an Indian made Stirling engine fan. When it arrived it was clear there were issues and so far I have sorted the main (?) one which was a bronze bearing was out of place causing binding. Its now pretty free running, I am aware Stirling engines in general can be quite sensitive in this regard. However the engine is not yet running. The flywheel is attached to the crankshaft by a socket grub-screw through its rim but there is no indication as to where on the crankshafts circumference it should be secured. I have photographs showing the crank is in the uppermost position and the flywheel, which I have tried at various points, so I could really do with some advise as to how to align the engine parts in question as this affects the piston position.

I should add that at one point it felt like it wanted to run but did not quite, but backwards. Any help would be much appreciated.

Chris.

Try adjusting 180° out and note the change.

Usually the crankpins are set 90 degrees apart. Looks in your last pic like the displacer crank is at TDC but the power pistons crankpin is at about 4 or 5 o'clock, so a little bit out. Maybe try moving the flywheel so the central displacer crank is at top dead centre and the flywheel crankpin is at 3 o'clock.

From memory - which is vague - the displacer (centre in this case) crank leads the power piston by 90 degrees. So if it runs the wrong way, as Mark says above, move the flywheel 180 degrees to reverse the direction.

Two things stop Stirlings from running mostly: Friction that absorbs the little available power. And leakage around the displacer con rod seal or around the power piston or at some point in the connecting ports etc.tini

The fan looks like a beauty. More pics would be much appreciated. Let us know how you go getting it running.

Edited By Hopper on 25/04/2020 01:27:15

As hopper says 90 deg would be a good starting point and the displacer leads

Is the fan well balanced? I see it has a large flywheel to smooth out the running, but that looks to be a large fan. Even the flywheel may not be too well balanced either. Every little bit helps with Stirling engines.

Thank you Mark, Hopper, Jason & NDIYet, thats most helpful, I will try again today and get back to you.

Hava great day

Chris.

Ok Progress! (-: Thanks again to all so far, especially Hopper for going into detail, as a novice engineer spelling it out to me is what I needed!

This morning I set it at TDC & 3 o'clock and off it went...backwards. Re-set at 9 o'clock it ran forwards for maybe 5 mins...happy as a happy person can be (me, not the fan). I tinkered with the positioning and got a second run of similar time. Then I could not get it going again. Even though there seemed to be a decent flame still I tried putting more meths in and then I got a good run of maybe 15 mins, then it stopped. After lunch I will try with the remaining fuel, if it doesn't start I will refill the burner in case its fuel hungry.

Ok its now after lunch and restarted it ran for 15mins, so it wasn't low on fuel. Inside the vented body there is a funnel which you can adjust up and down, as it was at its lowest I raised it but could not get it to run. So lowered it again and topped up the Meths and it ran for about 45mins.

Seems quite temperamental!

More photos as requested, I took a video but don’t see how I can upload it??

Two more questions, the hexagonal bar horizontal to the power cylinder, any ideas what that is?

As mentioned one of the bronze bearings was out of alignment, when I removed the clamping plate that secures it (does that part have a name?) I noticed that whilst it has an oiling hole cast into it there is no corresponding hole through the bronze bearing.

To my mind there should be, otherwise the oil will mostly only travel down to the outside of the bronze bearing bush, not to the crank. If I should drill the bronze bearings what sort of size hole please?

Chris.

It looks like a sintered bearing (oilite type), so no problem?

Very nice fan you have there, Chris.

I think that the hex. bar is just a plug. Take it out and you would find a hole connecting the power cylinder to the displacer. Unless you are desperate to find out if I'm correct (or not), I would leave it in place, especially now you seem to have it running well.

Dave
The Emerald Isle

As Hopper says, Stirling engines seem to be very sensitive to friction and leakage.

Really, the power is provided by atmospheric pressure acting on the underside of the power piston as the air on the other side cools, so not a huge pressure differential.

If the engine comes to a halt after running fro a time, maybe heat soak is taking place and the temperature differential is decreasing. Although the increasing times suggest that maybe it is running in and friction is decreasing?

Always amuses me to think of applying heat to an engine, in the room, so that it will circulate air to cool the room, or the people in it.. But I have always been a bit odd!

Howard

Thanks Not done it yet & Dave,......My understanding is sintered bronze(?)/ oilite is oil impregnated bronze, so no need to drill through, but still add oil which will seep through the bearings to lubricate the shaft?

Yes its quite the statement at 26" tall. I'm in no rush to remove the 'plug', though the bright metal parts appear to my eyes to be nickle plated and I'd prefer them un-plated, so have considered taking it apart to do this....but as you say now its running albeit temperamentally....

Cheers

Chris.

Hi Howard,

Well not that odd! And don't forget the fumes from the burner too! Before the final run of the day I had opened the workshop door to let the mass for fumes out, then couldnt get the engine to run. Then thought I'd try shutting the door...and it started right away!

Yes hoping it will run itself in, before the fumes do me in that is!

Cheers

Chris.

Chris V says: the bright metal parts appear to my eyes to be nickle plated and I'd prefer them un-plated ...

My experience of modern Nickel plating is that you won't have long to wait. Especially if the atmosphere is moist.

Cheers, Tim

Always amuses me to think of applying heat to an engine, in the room, so that it will circulate air to cool the room, or the people in it.. But I have always been a bit odd!

Not Stirling, but my step son in law has been using his TEG driven fan to circulate warm air throughout his bungalow for several years - and it still keeps running. Their wood burner is at the end of the building and the rooms at the far end of the hall were always cold cool before he bought it.

I wonder if the hex fitting is a speed control that you screw out to let a bit of pressure out of the system to slow it down? If not, then just a plug for the drilled passage as suggested.

Sounds like typical Stirling engine running for a period until the heat from the hot end of the displacer cylinder creeps up and heats up the cool end. The engine runs on the temperature difference between the two ends of that cylinder. So sometimes, the smallest flame possible will run it for the longest becuase it takes longer for the cool end to get overheated. The cone you mentioned may be for the purpose of keeping hot combustion gasses away from the cool end so some adjustment there might help?

She looks like a beauty! Is it an antique or are they still available in India?

I think they work on the principal that in the humid tropics a bit of extra heat from the burner is more than offset by the breeze from the fan that helps the sweat on one's brow evaporate and cool the body.

Edited By Hopper on 26/04/2020 01:07:13

Surely main purpose is to circulate air from a stove? I gave my son (who has 2 woodburners) one of these and it works brilliantly.

As hopper says main use of the fan was in the colonies to get some air movement, why else would one of the popular makes be "Lake Breeze". heat given off by the burner would be no more than it would if you had an extra Tilley lamp or similar going and why would they have had burners if going to be placed on a stove?

Thank you Hopper, I took a look to check this morning at the hex part and although it appears to be screwed in place it doesn't want to move by finger pressure alone so I will leave it as is at least for now. It may well be a plug as suggested but seems to me odd that its so large, and the shape does not suggest to me its a knob as such for adjusting.It continues to the other centre cylinder as far as I can see, but as I say appears to be a separate part ie screwed to the rest of it.
I will look at my album of Sterling's in a bit to see if its there on an original.

Yes this is a reproduction 'Josts' patent fan, (German) cheaply made in India though not so cheap to buy off eBay.Its a fair approximation of the originals which were made exactly for the purpose you mention. When electricity came it killed the idea off right away.
Look for Kerosene fan on eBay and you will find some, though I have to caution the buying experience was not a pleasant one!

John yes I took a look at your link, those are modern versions made for wood stoves and as Jason points out they don't have their own heat source. I'm sure they work well and are ideal for wood stoves.

This mornings questions:

Is there an alternative easily available in the UK to Meths to power it, ie one that dosent give off so much fumes?

Is there a rubber (or alternative) that I can get or make washers from for the sliding side screws to adjust the internal funnel that will withstand heat?

How do I add a link to here with a video?

Thanks

Chris.

I saw some of those types of fans still in use in India and Burma 35 years ago. Better than nothing in the tropics for sure. Back then, there were whole timber mills still running on steam engines. And steam trains as inter-city transport. An engineer's dream holiday.

Video you have to post on YouTube then use the You Tube icon at the top of your forum post to call up a box and then you copy and past the EMBED code from the SHARE option on YouTube. Clear as mud? Good. It's just like living in the 1980s on this site.

Neoprene washers will take a certain amount of heat, as will teflon, but not sure how hot you need. Might need something like phenolic fibre?

Depending on how your engine is made, a fibre washer or gasket between the hot and cool ends of the displacer cylinder might help stop heat transfer and keep it running longer. As might putting an ice cube or two on the top part by the handles there to cool that end off a bit.

Edited By Hopper on 26/04/2020 12:47:50

Edited By Hopper on 26/04/2020 12:53:31

Interesting engine, they're also called Radio Fans.

They seem to burn Kerosene (UK Paraffin) rather than Meths. That might fix the performance problem because there's roughly twice as much heat and a higher flame temperature in paraffin compared with meths. Meths is also likely to stink when used in the wrong sort of burner.

In normal times White Paraffin is easily had from Garden Centres; it smells less than Pink and Blue. The latter used to be dispensed from coin in the slot machines in garages and ironmongers but I haven't seen one for years.

Another thought, the original problem was due to off timing, and your fan may benefit from more tweaking. Most engines are fussy about timing - steam engines won't run if the valve timing is off and petrol engines are picky about spark timing as well as valve timing.

No spark or valves in a Stirling, but the time relationship between the power piston and the displacer may be critical for best results. Although the correct setting will be close to 90° it's worth looking for an optimum within, say, 10° either side. For the engine to turn, air cooled due to the main piston doing work by driving the fan has to be replaced at the right moment by timing the displacer 'just so'. Too early and too late displacer movement will both stop the engine, and there's a sweet spot somewhere in between. The fuel matters as well; an engine designed for paraffin won't take well to meths and vice versa.

The engine could be tuned for maximum power, or maximum efficiency, or maximum torque. They will all be near the same setting. What's wanted is the combination of those 3 that produces reliable starting and running. Note that tuning for maximum power (ie fan whizzing round at top speed) may not be the best setting for reliable running. It can only be found by experimenting.

Tuning is really a matter of patience; the main problem was getting it to run at all. Well done!

Dave