Bengs, Flame Eater. "Nick".........

[Stilldrillin]

Hi Chaps.

Had a frustrating, past few days. Can't quite get my thoughts, around the vague idea I have. For another Stirling. 

The recent grimey weather has kept my creaking joints, out of the shop. 

Then, there's the spring cleaning...... 

Then, the once I actually did get in there. At the door, a plaintive voice began shouting, "I want to play with Grandad!" Game over.......


So...... I had a look in the toy cupboard.

This came to me, around 3 years ago. A Bengs, Flame Eater. "Nick".

It needs a burner.........




Don't like that weird "chimney"........




Only 1 flywheel.......





But...... This one is different to most of my orphans!



It RUNS! Sort of........

David D

[tom osselton]

Well I've never seen anything like that in my cupboards!  where do you find all these?

[Stilldrillin]

Hi Tom.

I have been a member of the Steam Toys forum, for many years...... http://modelsteam.myfreeforum.org/index.php

At one time I had 26 engines in my collection. Then I moved away from steaming, to repairing, interesting engines.

This, and several others, came from members. Also, there's Ebay......

David D

[vtsteam]

That's a beauty, David!  Looking forward to another of your fine jobs on the burner and chimney. 

[fcheslop]

Dont know who has been giving you funny ideas about Stirling engines .Just bash em with a hammer.
Any update on the flame licker
cheers

[Stilldrillin]

Thanks Steve! 

Frazer.
If I could bash wiv an ammer, the way you do. I'd be a clever man........ 

Update? Funny you should ask that!


I finally managed some shop time, this afternoon! 

Started work on the burner.

Silver soldered the top, into 15mm x 40mm copper pipe. Then drilled for  wick holder and filler plug.

Like this.......




Experimented with the smallest dia wick I have, (4mm). To determine the optimum wick height.

Shortening the wick tube, 2mm at a time, until the engine doesn't want to run.

Then, packing under the burner, back up to working height. Will next, make a tube of the correct length.........




I found revs would improve, with a temporary "canopy"........




Think we need something more permanent, above the inlet port.

A few steps in the right direction. At last! 

David D

[Stilldrillin]

Still not finding much enthusiasm, for this refurb. Dunno why........ 

Finally got the burner finished! 

Soldered in, the wick tube and filler bush. Then fluxed, ready to install base.

Rather enthusiastic with the plumber's solder.......




Stand upright. Heat the base, until the solder seeps through.......




Tried two different types of wick medium.

Pipe cleaner......




Fiine copper wires......




Neither were as good as the fibreglass stove rope I usually use.




Next up. I'll have a look at the valve area. If I can find a small enough tubular spanner for the pifflin' nuts.....

David D

[Stilldrillin]

It's all held together with M2 threads, having 3mm a/f nuts. The same as the socket in an M4 caphead. 

Reduced the head diameter as far as sensible. Then drilled 2mm x 1/4" deep, to clear the longer thread.

Couple of locked nuts, for a handle........




Works a treat!

Not happy with the lack of "compression". No head/ cyl seal, won't help! 

The slot for the poppin up n down valve, seems to be a bit deep. At 10thou clearance.......




Gave everything a rub on fine emery. Reducing slot depth, to give 5thou clearance.......




All back together now. Awaiting the chance to give it a run...... 

David D

[vtsteam]

Took a little head scratching to figure out what you were doing, David! 

That big steel bolt was just used as a combination wrench socket and extension -- not an addition to the engine. And by turning down the diameter of the head -- you mean the head of the bolt, not the engine. Sorry, a bit dense here sometimes! 

Is the lack of compression due to a leak or too much head space? It does sound like tightening up the valve clearance will help.

You have got me thinking about the problem of a vacuum engine valving......

[vtsteam]

Isn't the power stroke a vacuum, and not a result of compression on these?

[vtsteam]

To optimize, you'd want a very free exhaust. Big port. Chimney looks like a restriction. A chimney could be big bore, or extractor cone, finned, maybe to rapid cool and act as an extractor.  Fun to think about this stuff. 


How does this open for exhaust? a second one way valve on top? It must be very short timing on exhaust...


Floating disk valve, maybe. Maybe no spring, Does the screw set the clearance, or the spring pressure on the disk. Or is it a flapper? Floating disk would be better. Could be a ball, but more inertia -- slower acting. I'd vote for a disk.

That valve inertia is critical to power output. The faster acting, the more power.

[Stilldrillin]

Took a little head scratching to figure out what you were doing, David! 

That big steel bolt was just used as a combination wrench socket and extension -- not an addition to the engine. And by turning down the diameter of the head -- you mean the head of the bolt, not the engine. Sorry, a bit dense here sometimes! 

Is the lack of compression due to a leak or too much head space? It does sound like tightening up the valve clearance will help.

You have got me thinking about the problem of a vacuum engine valving......

Hi Steve.
Thanks for your interest....... 

Correct. On the "big steel bolt". Which is a pifflin' 4mm dia.
I turned the caphead down, to easier fit on the other nuts, which were holding bearing caps etc.

Lack of "compression". (Note inverted commas). Is down to several little leaks. Aint got no valves. As such.
It should make squarking noises, rotated forward. And, lock solid against vacuum, in reverse.

Isn't the power stroke a vacuum, and not a result of compression on these?

Yes!

To optimize, you'd want a very free exhaust. Big port. Chimney looks like a restriction. A chimney could be big bore, or extractor cone, finned, maybe to rapid cool and act as an extractor.  Fun to think about this stuff. 


How does this open for exhaust? a second one way valve on top? It must be very short timing on exhaust...


Floating disk valve, maybe. Maybe no spring, Does the screw set the clearance, or the spring pressure on the disk. Or is it a flapper? Floating disk would be better. Could be a ball, but more inertia -- slower acting. I'd vote for a disk.

That valve inertia is critical to power output. The faster acting, the more power.

Vacuum..... Therefore no gasses to exhaust.

The piston created vacuum, draws in the flame. Which cools, to draw the piston back to tdc.

The "chimney", houses a 6mm dia rubber ball. A one way valve. To allow any unwanted compression out, during overlap.

The only valve, is the sliding shim. Sealing against the face of the cylinder head, during the vacuum stroke.

David D

[vtsteam]

...The "chimney", houses a 6mm dia rubber ball. A one way valve. To allow any unwanted compression out, during overlap.
David D

That's what I meant by exhaust and exhaust valve.

The vacuum created is only partial and reduces to positive pressure as the piston moves back to the head end.  That pressure is made up of the cooled gasses from the prior combustion. They contracted but didn't disappear.  These must be exhausted as much as possible at TDC before drawing in the next charge of hot gas. They otherwise cool it and reduce the displacement available.

This conversion from vacuum to pressure happens near TDC, so exhaust interval is extremely short. Valve action must therefore be very snappy. That means a low inertia valve, yet one with low spring pressure, since exhaust pressure is low, too.

As a guess, a thin metal disk valve would have faster action than a rubber ball, so might offer the opportunity to increase performance. That's what I was mulling over. I could be wrong, but it makes me want to experiment along those lines. Too bad I'm stuck on the tractor, for the near future. And rain yesterday, today, and a real downpour predicted for tomorrow.

I think your engines are just wonderful to follow, and they make me think a lot.

[Stilldrillin]

Steve.
The one, main thing, about my orphans..... There's lots of scope for thought and experiment! 


Well........
The run didn't go well. Stopping every few seconds. 

I realised, the engine didn't spin over, as it had done previously. Possibly out of alignment, after I had tightened all the loose nuts?   

Time to strip further!

Piston. Scuffed one one side. With what looks like ptfe tape packing.........




That's not original, surely? Made from 16mm bar. Not machined on the o/d.........




Looks like the oiler insert was a bit long. And held fine bits of swarf..........




Better  view. Bore is badly scuffed, on the other side to the oiler........




Time for a rebore.........




And hone........




Sheesh! 

David D

[fcheslop]

Oh dear the joys of hot air engines
That will keep you busy marra.Never seen a piston like that one.
Vac engine principles Jan Ridders has  good animation
http://www.ridders.nu/index.htm
cheers

[Stilldrillin]

Frazer.
The next piston won't look like that one, either!   

Just got to decide, what material to use....... 

Interesting animations and info.     Thanks!

David D

[fcheslop]

See other channel
cast iron if you dont want to get in bother.Iv two graphite bits to make and I hate the filthy stuff but needs must
Wor lass winnet be pleased
cheers

[Stilldrillin]

By 'ek! It's more than two months, since work stopped on this engine! 

From the last line, of the last post. I actually did, "get on with it", at the time.........

Turned a 12mm dia mandrel.......





Then turned/ polished the piston to a nice fit in the cylinder......




Temporary assembly. Losing one of the M2 nuts, in the process.

It still runs!  Now, needing no warm up! 

I now, need to think of an "eyebrow", over the flame/ port area.

And, that's the point where it all stopped........   

David D

[vtsteam]

Runs very nicely, David! I like the solid appearance of that engine, too. The parts look robust, and it gives the impression of power to see masses swinging around -- even if the actual power is low. Excellent little engine!

 

[AussieJimG]

Well done David, it is always a pleasure to follow your re-builds.

Jim

[Stilldrillin]

Steve, Jim. Thanks for your kind comments!


Well..... I'm still here Chaps!

Isn't it amazing, how life gets in the way of progress!   

Modding a handy electrical conduit widget. I fitted the compound slide to my little lathe, and extended the outer taper, at 2.5*.

Then bored the inner taper, at 2* to give a slightly thicker wall, at the head end........




Made a disk, to suit the cylinder head pattern. Recessed to suit the tube.

Silver soldered in place. Tidily. Using minimum flux and wire.......




Milled a 10mm slot, and assembled........




And. It's working even better, now.......   

Can anyone tell, what I'm muttering about? It seemed quite relevant at the time!

The engine's in pieces now. Being smartened up.
I don't do polished n shiny. But it will look a whole lot better when next you see it.   

Thanks for dropping in!

David D

[Stilldrillin]

As I'd got the engine running better, it was time to sort the other niggles.......

I wanted the flywheel, on the other side. So, needed to reverse the crank assy.

Shutter arm sleevelocked. All in line........




Cross pinned.........




Eased, here n there. Just to make sure, there was room to swing an arm.......




Varnished, painted, polished. Bearings tightened. I still didn't like the tractor exhaust........




So, I made a pepper pot muffler. It quacks, now!

Adjusting the screw, alters the pitch........




Alloy pulley. To cover the spare shaft........









Video........

All done! Don't like the burner, much. That's a job, for another day...... Or year! 

Thanks for watching!   

David D

[dawesy]

Lovely little engine and very nicely finished.
Really good videos. Show how much better it runs compared to the beginning.
Top work

[millwright]

Another one nicely ressurected David. Amazing the difference it has made to the running. Top Marks to the man again 

John

[Stilldrillin]

Lee, John.
Thank you, for your kind comments.   

It's a good feeling, when an engine saga comes to a successful ending. Even better, if it's been appreciated.......   

David D