Gas Firing the Scott Vacuum Engine..........

[Stilldrillin]

Many of you, will remember my Scott build.
 For those who don't, but have plenty of time. It's here...... http://madmodder.net/index.php/topic,10164.0.html





It has run, faultlessly, (so far), "straight out of the box". Two shows, at some 6 hours each. Plus, my own pleasure runs.

The only bugbear, has been refilling the meths burner, every 25 mins. The paint, doesn't like meths.......

Time to go, gas fired!

Bought a tank, from Forest Classics, at the last show.
 Mounted on 3mm thick aluminium x 50mm wide.
The wooden bearers are 47mm apart. I milled a rebate along the inner corners, allowing the alloy strip to slide underneath, like a drawer. The weight of the engine will, (probably), hold it in position.




It needs twin flames. So, it needs a T piece, as the burner base.

1/2" brass bar, with 5mm, (M6 tapping size), through holes. Slot drilled, to centre line......




Flux, only where it's needed. Silver solder........




Mount like so. Apply heat.......




Happy, with that........




The burner's main components.......




Further progress. As, and when.......

Thanks for looking in! 

David.

[Manxmodder]

Hello David.
Glad to see you back on here doing a bit more tinkering,and I can see why you're very happy with that silver soldered Tee piece  Turned really nicely.

Last night I was browsing your thread about the 3 cylinder Mamod steam engine refurb on Model Engine Maker.

Very tidy engine she is too

Look forward to your next instalment.......OZ.

[SwarfnStuff]

I, like many others on this forum, recall following your first thread on Scotty, one of your several orphan engines with interest. So, it will be with interest again that I follow the Gas firing of Scotty.  Looking again at the previous thread and thinking a tad more I wonder if two burners are really needed or if you could create a wider flame face with a tee at the burner tip? BUT, hey, you have started already and will create another great modification. I await the next installment. Your post are always worth a coffee and read. 
John B

[Stilldrillin]

OZ, John.
 Aww..... Thank you! It's good to know my fumblings are appreciated. (Please have a quiet word, with Mrs. Drillin). 


Today's instalment.

Assembled, and gas turned up. We've got twin bunsen burners.......




Add a couple of caps.......




Already, it's a rapid runner. I've now found the revs are limited, by the follower coming off the cam........




The uprights are too high, at the moment. I will experiment with packing under the engine, before reducing their height to suit.

I'm thinking of installing a small pilot light. As the engine still insists on blowing out the flame, when it's too close to the port.
 But, that might change, with a lower burner height.

David.

[John Rudd]

Burner certainly looks impresseive David...l

What number jet are you using?

[Stilldrillin]

Burner certainly looks impresseive David...l

What number jet are you using?

Thanks John.
 It's a No5. Cos' I can't find a No3, anywhere....... 

"My", type of engines, need very little gas. Compared to the available equipment, which is set up for steaming boilers.
 I have to Mod the tank's needle valve, to give a slower taper. Even then, ¼ turn open is too much!

Phil, of Forest Classics, says no-one has any No3 jets in stock. His supplier, will make him, 2,000..... Minimum. 

Does anyone know where I can buy/ beg/ borrow/ steal, a No3 jet?...... Please!

David.

[SwarfnStuff]

As usual, Brilliant work.  Love the burner flames. Now just need to see the video. Congrats,

Bloomin Marvelous.
  

[philf]

Does anyone know where I can buy/ beg/ borrow/ steal, a No3 jet?...... Please!

David.

David,

Plenty of people seem to make their own jets using clock bushes. You then only have to drill a reasonable sized hole and press the bush in. I found reference to a number three jet having a 0.15 mm hole. You can get bushes very cheaply in 0.14 or 0.16mm hole sizes.

I just found a supplier in Northern Ireland who does them for £0.75/10 + postage. Unfortunately postage seems to be £3 so you'd be better ordering a few sizes. There are probably lots of other suppliers but some have a minimum order value.

http://www.nwcsupplies.com//index.php?main_page=index&cPath=70_1381_1385

I have some 0.16mm bushes but they're watch bushes and are only about 0.5mm thick overall with an oil sink set in so the bore will be very short and may not be suitable.

I've just had a look at my drills and my smallest is 0.24mm otherwise I'd have had a go at making one on my watchmaker's lathe.

Cheers.

Phil.

[awemawson]

Have you tried PCB drills? They come in all sorts of tiny sizes and are cheap as chips on ebay:

http://www.ebay.co.uk/itm/10pcs-Pro-PCB-Print-Circuit-Board-Carbide-Micro-Drill-Bits-Tool-0-1mm-to-2-0-mm-/400950208588?var=&hash=item5d5a7ea84c:m:mVM6zyehgI5kwzP8m0y3QnA

[Stilldrillin]

Love the burner flames. Now just need to see the video. Congrats,

Woa! Steady on, John....... 

There's a lot more faffin' about to do, before another vid.

I was hoping to get two precise flames, pointing straight down the ports. But, the engine is like a daft kid, at the moment. As soon as  it gets going, it blows it's light out! Can't get a gentle flame, close to the port. 

It needs the root of the flame, low down. Out of draught's way.

Which angle of attack is preferable........



I think 45* gives best presentation.......




I will probably make up, a couple of copper pipe, uprights. Mebbe! 

David.

[tom osselton]

Just wondering what size orfice a bic lighter has.

[modeng200023]

I have been looking for clock bushes but they seem to have too large a hole.
However watch bushes might fit the requirement. Here is the link to Cousins site.

https://www.cousinsuk.com/product/watch-bushes-by-size

Hope this is useful

John

[Stilldrillin]

Plenty of people seem to make their own jets using clock bushes.

Phil.
 Yer a GEM! 

I've just ordered a pack of 10off,  at .12mm. This is smaller than No3, as fitted to the Huxtable and Robinson engines. Both of which could stand a further reduction in jet size. 


Thanks, Andrew.
 That's a good thought.......

I hate to think how short a life those little drills would have, in my Mini Lathe.......

We'll see just how tiny, Phil's bushes are. In my fumbly fingers. 

Thanks, again Chaps!

David.
 

[Stilldrillin]

Tom, John.
 Sorry. I was typing as you posted! 

They are good thoughts, if the french clock bushes don't work out...... 

Thanks, Chaps! 

David.

[Manxmodder]

David, I agree with your logic of trying to get the root of the flame below the snuffing effect of the blow out point.
45 degree angle looks a good start to me 

Yer old joints may be getting a bit dicky,but there's nowt wrong with yer logic there lad 

The mention of watch bushings also reminded me that I had considered ordering a pack of these broaching wires a while back.

 Link: http://www.ebay.co.uk/itm/10-WATCH-CLOCK-CUTTING-BROACHES-SET-0-3-0-8mm-FOR-BUSHING-SERVICE-REPAIRS-/400873870784?hash=item5d55f1d5c0:g:cQIAAOSwBLlU8aME

.....OZ.

[SwarfnStuff]

He, he, well I shall just have to have another or two.

     OR, I could do some more messing about with my attempt at Jan Ridder's Coffee Cup Stirling. Blimey they are fiddly, got it to run in a lumpy fashion then fiddled some more to (Improve it) and it refused to go. Next, after a pull down, fiddle, bung it back together and it ran anti clockwise (had timing offset 'tother way round) but also ran lumpy. Being about 1/20th of a mosquito power, friction and balance are the enemy. Taking it to my local Model Engineering club tomorrow to see if the chaps have any idea of what I'm doing wrong.

     I agree with OZ that the 45 deg angle of attack looks good. That said, looking again at the two flames the 90 deg just might be easier to set below the snuff out zone.
John B

[Stilldrillin]

OZ.
 Thanks for the boost to my confidence!
Which has now, just suffered a big knock.    See further down page........

John.
  A few more coffees to come,as yet........
I hope your coffee cup stirling, is now running like a good 'un! 

I wonder why many, start with a coffee cup, or pifflin' tiny engine, with little power?   
 I started with Gold Blend. So big, it had to run! (And, still does).   http://madmodder.net/index.php/topic,5732.0.html


Anyroad!
I've had one of those moments......... An epiphany....... When you realise, you've had it all wrong. For so long........ 

Yesterday's workshop weather, bit me.
 Staying in, today. Chance to test the various burner angles.......

Only place available, is on top of a wardrobe. At forehead level. Mrs. Drillin doesn't complain too much, about gas smells...... 

All the various terminals performed, exactly the same as each other! Always, the blummin light, blew out!!!


Standing where I was. Looking up at the burner. Never observed from this angle before.......





The light's not being blown out....... It's being sucked out!!

Very difficult to photograph. But, obvious to the Mk1 eyeball. The intake velocity is greater than the gas velocity........

Puts a whole new slant on things, don't it? 

Sheesh!

David.

[Manxmodder]

All seems so bleedin' obvious now you've seen the problem first hand 

I'd wager that the solution may not be quite so easy to arrive at. Time for a bit of further  experimentation methinks 

....OZ.

[Stilldrillin]

Thanks OZ. 

You're right! Here we go!


My thoughts, are now running along the lines of a soap bubble. Easily taken from it's ring. Mod the orifice, to make it less ring like.

Milled a 4mm slot, in the 5mm bore terminal.......




Burns well.......




Cam follower bounce, at full blast.......




But. That's not what we're here for! I need it to run reliably at around 150rpm. And, wind up, as necessary. 

Sleeved down, to a 3mm orifice.......




No! ...... Not enough gas! Needs a larger bore terminal.

The one thing this has proved. It works perfectly well, when the burner is outside the shroud. The vacuum kills the flame, when under the shroud.

I'm now steeling myself, to remove the sides, (or all), of the shroud. Without any collateral damage to the polished cyl head...... 

David.

[Manxmodder]

"Cam follower bounce, at full blast"....... 
I guess Desmodromic valve gear is out of the question 


On a sensible note maybe just a couple of holes drilled in the sides of the shroud would be enough....OZ.

[Stilldrillin]

"Cam follower bounce, at full blast"....... 
I guess Desmodromic valve gear is out of the question 


On a sensible note maybe just a couple of holes drilled in the sides of the shroud would be enough....OZ.

Hi OZ.
 Desmo? No chance! For now.......

Your, "couple of holes", gave me pause for thought.........

Then I thought...... Nah! .......




And made this racy little, cut down number.........




Will probably, make some longer horizontals. From stainless steel...... 

David.

[Stilldrillin]

Does anyone know where I can buy/ beg/ borrow/ steal, a No3 jet?...... Please!

David.

David,

Plenty of people seem to make their own jets using clock bushes. You then only have to drill a reasonable sized hole and press the bush in. I found reference to a number three jet having a 0.15 mm hole. You can get bushes very cheaply in 0.14 or 0.16mm hole sizes.

I just found a supplier in Northern Ireland who does them for £0.75/10 + postage. Unfortunately postage seems to be £3 so you'd be better ordering a few sizes. There are probably lots of other suppliers but some have a minimum order value.

http://www.nwcsupplies.com//index.php?main_page=index&cPath=70_1381_1385

I have some 0.16mm bushes but they're watch bushes and are only about 0.5mm thick overall with an oil sink set in so the bore will be very short and may not be suitable.

I've just had a look at my drills and my smallest is 0.24mm otherwise I'd have had a go at making one on my watchmaker's lathe.
Cheers.
Phil.

Hi Phil.
 A little packet from, Rafferty's Hill, County Down. Arrived today........





I was expecting, 10off bushes........ To me, these are 25off, "gear spindles". 6mm oal, .95mm o/d, .35mm x 1mm spigot. 

Until, I donned my BINOMAG........ There's a hole through the middle!!! 

Good job, I've got a few spares....... 

David.

[philf]

Hi David,

Not what I was expecting either!

Is the hole through the whole thing or just the spigot on the end?

I may have some of those somewhere.

I hope you can still use them - if not send me the bill!

Cheers.

Phil.

[Stilldrillin]

Phil.
 I'm pretty sure, it's the right sized hole. All the way through....... 

I just need to find a fine piece of wire, to prove it.

There's a whole lot of "No2" jets here. If I can find a delicate method of parting off......... 

David.

[Stilldrillin]

Heading the right way, I think...... 

Slow running test..........

Going to shorten the verticals by 1/4".

David.