Scotch Egg

[paul]

Here's a pic of progress so far on my Scotch yoke / rotary valve engine. I thought 'tiny twin' was small but it looks rather beefy towering over this daft little engine! (Witness the 5 x 6 x 1.5mm brass sliding block in the yoke)



Not really much left to do:

• Make the crankshaft - the tricky bit - and web
  
• Make the flywheel - anything will do
  
• Shape the bracket (might not bother)
  
• Make the base
  
• Clean off the superglue splodges
  

Despite it's 8mm bore the piston has got a right suck on it! First time I've used cast iron (for the cylinder) since I bug****ed up the cylinder/port block for my 'long term' project. Seemed to come out ok.

If this one works on the aquarium pump I'm going to make a seriously beefed up version for a laugh.

;D

[baggo]

Hey Paul,

if you go any smaller we'll all need magnifying glasses! ;D

John

[paul]

Haha, I didn't realise it was quite so small until I made the first bit and it was too late to turn back then as I'd have wasted 20p worth of steel!

[jgb7573]

Good to see you plugging away and having fun Paul. Keep up the good work and keep entertaining those of us who haven't got the workshop back together after a house move yet! Jolly good fun!

[paul]

Cheers John, this one is fun.... mostly because there are only about a dozen parts to it!!

[steam4ian]

G'day Paul.

Is your "scotch egg" an Elmer design? I think Elmer was a frustrated watch maker judging by pictures of him peering through the bottoms of "coke" bottles and the size of his models.

Is the steam/exhaust controlled by a rotary valve on the crank shaft?

BTW, I got my double acting oscillator running at the weekend. It uses only a puff of air, the gauge doesn't move off the stop, but more than I can blow. Must post a picture, I have pictures of the components, you've shown me yours......

Regards,
Ian

[paul]

Ian, yes it's the Elmer Scotch yoke with rotary valve/crankshaft (what a neat idea!!). I plan to build either a double or triple scale version if this one runs or maybe 'double scotch' (the opposed twin version). Actually I've also been trying to come up with a double acting version but it makes my head hurt!

Anyway, let's see your parts (so to speak!) - I'm sure all of us mini-engine builders on here would appreciate it. Don't be shy

[paul]

Latest progress and not far off done now; just need a flywheel, a crankpin and to drill/file the crankshaft/valve. Oh and maybe tart up the bracket

[havoc]

Nice job. I love the techy square look.

[paul]

Thanks mate - it's only like that because I couldn't be bothered to do the fancy bits on this 'experimental' project

[paul]

Nearly there.....

Crank all done, flywheel mostly done, bracket...er....
Ohe just remembered need to make a slot in the yoke to let the steam (or air) out (the sharp-sighted may see the steam 'ole in the end of the crank)

[paul]

Even closer... still just that damned bracket to file. Maybe ;D

Stuck it on the aquarium pump tonight and was very pleasantly surprised to find it turning a few revs by itself at first assembly, despite the fact that the end hole (used for drilling steam passage) hasn't been properly sealed yet.

[jgb7573]

Smashing!

[circlip]

Are you going for the French one from the other site next Paul?

[paul]

What French one mate?

[circlip]

French steam engine - Jagwinn - plans - hmem?

[paul]

Oh, I haven't seen that one - I was eyeing up Elmer's 'Beam' ;D

EDIT: I lied I downloaded that from elsewhere ages ago... a bit too much for me at present, I'm sticking to the small & simple variety for now ;D

[paul]

Can't get this one going on air - there's just too poor a seal between the flywheel and the bearing I think. Need to get the boiler done pronto so I can give it a blast, I'm sure it'll run with 40 or 50 psi of steam up it's back end

[paul]

Connected it up to the new boiler ce soir and it didn't want to run; I think I might need some proper steam oil. It's smooth as silk when turned by hand but felt 'crunchy' when I tweaked the flywheel when under steam... the whole thing also got incredibly hot. Pah!

Well at least the new boiler doesn't leak!

[dickdastardly40]

How much allowance for expansion did you design in mate?

Also ensure you warm it through and purge any water as that won't help either