Scott Vacuum Engine......

[Stilldrillin]

Introducing Scott. Another of my orphan engines.

Arrived a couple of years ago. Been patiently waiting in the cupboard. 

Never run. (I don't think)........




Badly packed, on top of the wad of drawings. Which were penetrated by the crankshaft....... 




The shaft was bent, and flywheel distorted.
Rather proud of myself, at the time. I made a ballrace nudger. Which got it back, to within a couple of thou'. 

As it arrived. It was impossible to screw the valve mechanism together, tight enough........




I dimpled the cross shaft, for the grub screw. Then made a temporary return spring........




No joy! The shutter arrangement is much too light n floppy. Had a few pops, only.

After I'd caught my finger in the guillotine, for the third time. I decided it was time for some mods.......




So......

The engine part is fine. The valve part is 'orrible.

I need some info, as to which is the best system to get the flame safely into the cylinder, at the correct time.

Some systems are eccentric driven, rather than a cam. I guess that is for quicker open/ close action.
But an eccentric will give positive motion, in both directions.

I can visualise a push/pull or twisting rod, along the side. How does it turn the corner, to the port?

Anyone any ideas? Crap o cad/ pics/ vids, gratefully accepted.

David D

[tom osselton]

Here is one by bogstandard
http://www.modelenginemaker.com/index.php?topic=158.0

One site said they made the graphite valve come down so the flame doesn't have to go over it.

[Stilldrillin]

Here is one by bogstandard

Hi Tom. Thanks for the link! 

That particular valve train, is a very unreliable system.
I'm minded to Mod it, the same as my last project. The Bengs, Nick.....  Can't be any worse than it is! 

David D

[Stilldrillin]

Progressing. Slowly........   


Roughed out a slot, in the c/i base...........




Milled a matching slot, and 4 retaining holes, in the hopper........




Matched up, nicely........




It needed a widget...... M3 thread in one end, 3/16" hole in the other, and a 9degree bend in between.

Turned the big end, and tapped m3. Held in the rotary table, at 9*, spot faced and drilled 3/16, down to centre.......




On to a 3/16" mandrel. Turn small dia........




M3 studding. Turn radius........




Couple of flats. Loctited, to the tubular operating arm........




Bottom of stroke.......




Top.........




I'm quite pleased, how it's gone together, so far.

I've (finally), read up the Poppin plans, and think the lightweight valve is the way to go.
Bought some 5thou steel shim. If I can cut it, and keep it flat. I might be in with a chance!

The present return spring is much too stiff. I've made a better action, with a small coil spring, under the cam arm.
But, I don't want to abandon the leaf spring, just yet.

Does anyone know where I can get a sensible length, of 1/4" x .012" spring steel?

Thanks for looking in!   

David D

[PJW]

Hi Dave, I am watching with interest, I know nothing about vacuum engines so its look and learn. It looks like it will be an interesting engine when you have it running.

[Stilldrillin]

Hi Dave, I am watching with interest, I know nothing about vacuum engines so its look and learn. It looks like it will be an interesting engine when you have it running.

Hi Peter.
I don't know enough about these things, either! With me, it's fumble and learn...... 

Did you see my last one? http://madmodder.net/index.php/topic,9661.0.html

David D

[Pete W.]

Hi there, David,

"Does anyone know where I can get a sensible length, of 1/4" x .012" spring steel?"

A bit of feeler gauge stock might do???? 

[Stilldrillin]

A bit of feeler gauge stock might do????

Pete.

You're right! 

Why didn't I think of that?   

David D

[PJW]

Just looked at your last engine Dave, it a little cracker!  well done!
I do like the look of this one though & look forward to seeing it running, keep up the good work.

[Stilldrillin]

Thanks Peter!
Didn't enjoy the fumbling. Much too small n fiddly, for my old fingers. But, I love it now it's doing what it's supposed to do...... 


Feeler gauges....... Hmmm.....   
Not given them a thought, for the past 20 years, or so. No need, for modern vehicles. 

Just been rummaging, in my old toolboxes........




What a nice trip, down memory lane!

The central one. For my first motorbike. Came from the Brighouse branch of Woolworths, 1960. Cost 1s 3d.

The lower one was bought for my brand new, 1965 BSA Lightning.

The top one, when I went metric. Around 1980.

I've got all the spring steel I need...... Thanks for the posts, and pm's Fellas! Much appreciated.   

David D

[PJW]

there is a piece of spring steel in the old VHS tapes, some have a plastic spring but mist have steel,

Peter

[Stilldrillin]

Managed a few workshop minutes, this afternoon. 

Assembled. Then realised, I'd forgotten the leaf spring!   

The little coil spring, saved the day.......




Gave it a flick....... And it stuttered into life!!.......




You know that supreme moment.   
When the blood pressure goes sky high. And, all you want to do, is dance about, for joy.   

It's A RUNNER!!!!   


At that precise moment, SOMEONE, was knocking on the door........ "Grandad"....... Didn't know what to do! I nearly burst!


I had a Little Helper, for the rest of the afternoon.......

I bet Steven Spielberg, never had such a helper.......

Love it!

David D

[Kjelle]

Nice job!! Sounds like your little helper is a ray of sunshine, too!

Kjelle

[Stilldrillin]

Thanks Kjelle.
She's a lovely, little bundle of happiness. Especially, around Grandad......   


So much for the "wonderful" idea, of the original graphite valve, lubricating the piston and bore. No need for other lubrication! 

The vacuum chamber condensation, turned to rust, overnight! 

Another, fun d mental flaw? I seem to get a lot of them, in my rebuilds! Sheesh! 


Anyone know, where I can source 35mm dia graphite in the UK. At sensible cost?   

David D

[Stilldrillin]

Showing the original "Poppin", shim valve arrangement. It's a bit vulnerable........




So, I made a temporary guide arrangement. Shim, loose on the actuating arm.........





No chance, so far, of a piece of graphite. 
I thought this would do the job..... http://www.ebay.co.uk/itm/300839376964?_trksid=p2060778.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Until I ran the mouse over, to zoom. It's made of dried leafmold!   

Guess it will have to be a brass piston. 

The stainless tube has arrived, to sleeve the cylinder. See last pic.

A piece of 8mm stainless plate is on it's way, for the port face.

Progressing. Slowly...... 

David D

[awemawson]

Anyone know, where I can source 35mm dia graphite in the UK. At sensible cost?   

David D

David,

The attached pictures may be of interest - it's Poco brand EDM graphite from my stash of things potentially (Pun intended  ) to make electrodes from. POCO is a very fine grade of graphite for fine details

[Stilldrillin]

By, 'ek, Andy! 

Yer've got me attention, now!   

Switch to pm's, I think....... 

David D

[awemawson]

David,

Tell me how much you want sawed off the (presumably) 2" piece, PM me an address and give Eric a donation in my name to the running of the site for what you think it's worth to you.

I ain't turning it down to 35 mm for you - my lathe is reasonably clean 

[geoff_p]

For smaller lumps of graphite, such as your valve-block, I use carbon-brushes from/for electric motors.  The local motor-repair shop keeps them up to about 1cm-square section by 4cm long, of which the braided wire connector ruins a cm or so.

Am currently using this material for big-end bearings on my experimental 4-T petrol engine, where they take an awful hammering.

[Stilldrillin]

Progressing, steadily.

The runs I managed to film, were the only life I could coax out of this engine!
Days after, it still hadn't run again. 

Condensation left a dragging film, between piston and bore. Couldn't get the engine to spin.
Also, all other internal cast iron areas had a film of rust. 

Seems a pity, to break up this well matched partnership. But, it's time to go, rustless!




Bought a length of 35mm stainless steel exhaust, 1.5mm wall thickness.
The inner seam was some 8thou deep. So, I set it over in the chuck jaws, using a piece of 10 thou steel sheet. To ensure a deeper cut over the seam area.

Clocked parallel to carriage travel........




Cleaned up both ends, leaving a witness........




I could then bore, concentric to each end.......




Then, turn the o/d concentric to bore.......




There you go.......




Open up bore to +.002" on sleeve o/d........




Loctite in place. And skim the ends........




Now, waiting for my pal Dave, who's a whiz with a bore grinder.

Thanks for looking in! 

David D

[awemawson]

Nice work 

I like the trick of off setting the weld 

[Stilldrillin]

Thanks Andrew.

I'm just pleased, I thought of it. Before I started machining! 

David D

[Joules]

Lovely bit of work there David, always fancied one of these engines...  Must pull my finger out one day and make a start on one....................................................................................and finish it 

What mill do you have ?

[Stilldrillin]

Thanks Joules! 

The mini mill, is the one in my avatar.
A Chester Conquest. Modded, with R8 spindle, and belt drive etc. Works for me! 

David D

[dawesy]

Very nice. Good work.
Just as a thought if you ever need to do another is seamless pipe. I used some sch10 316L when making an exhaust manifold. It's a bit more expensive but has no seam to worry about.