My Mamod SE3+.

[Stilldrillin]

This is the still developing story of my 3 cylinder toy steam engine.

It started life as a standard, twin cylinder Mamod SE3 steam engine.

Probably one of these......
 




I do seem to have amassed quite a lot of other SE3 components! 





I wanted to develop a toy engine which didn`t rattle & clonk, or only sit there in a blurr of revs.

I was intrigued by Roly Williams triple. 

http://uk.geocities.com/rolywilliams/three_cylinder_mamod.html

But, I didn`t like the overlapped, stepped base giving crank alignment problems.....
I hoped my local car body repair shop could butt weld 2 decks together....... Not interested!

Sooo........ I had to compress the engine to fit onto the standard Mamod deck!

This is the first incarnation.






Various problems, including the 50% extra condensate trickling down the boiler, into the burner, and  a melted steampipe joint required a rethink / rebuild..... 

I rebuilt the inlet & exhaust systems, with a condensate collector at the rear of the cylinders.





Then I straightened and aligned everything, (as best I could with a toy) & bushed the big end bearings to give "nil" clearance. It still clonked!

I made a better fitting centre throw crankpin, which helped, but didn`t cure.....

This is the second incarnation.......





The condensate collector overflowed after only a few minutes running!
And it still clonked! 

Hmmmm........


Untouched since May `08, I started another rebuild this winter.......

The first alteration was a different design of exhaust system. Which cost me the price of a milling machine, and tooling......





Made up a more robust centre crankpin.
One end held by 4ba grubscrew, for dismantling purposes. The other end loctited into the crank.





I line drilled the cylinder pivots 9/64" & bushed them to "nil" clearance.





Lapped the cylinder & valve block faces to each other.

I couldn`t think of much else to do, to improve matters. 

THEN, someone mentioned plastic pistons....... 

[bogstandard]

David,

I remember many moons ago, having a little discussion with you about the collector tank. I should have realised then that you would have had trouble with it, by turning itself into a nice condenser tank, with no place for the water to go. 

But you have happily progressed a lot since then, and of course you have learned a lot on your journey, so all the different mods were not wasted, they should be classed as lessons in how not to do it.

Now that you have it running so well, have you given any thought about how you are going to take it to the next stage, if of course, there is a next stage to go to. Or are you now going to make something that will give it a bit of work to do?   

John

[sbwhart]

David

I take it then that a triple is not a normal Mamod engine,

It's very interesting what you've done with it and the interations you've gone through, for the next step have you considered fitting a steam valve linked to a governor, I'm sure that would be quite novel. 

Have fun

 

Stew

[sbwhart]

You could also try reversing the engine this could be done with four way valves I think 

I bet John would know how to do it.

Stew

[Darren]

I bet John would know how to do it.

Well I wouldn't join you in that bet, I'd be poorer 

[bogstandard]

John wouldn't.

Because they are only single acting, you can't control the steam to push them into reverse. But the engines should run backwards if you flick them that way in the first place, but that is assuming the ports are sighted correctly, which I don't doubt they are.

Bogs

[sbwhart]

Sorry John

Didn't mean to put you on the spot.

There's more to these little engines than meets the eye.

Cheers
 
Stew

[bogstandard]

Not putting me on the spot at all Stew.

You are quite right, all types of steam engines operate in different ways.

To make a single acting oscillator engine into a double acting one isn't as easy as it looks. All the port faces have to be redesigned and galleries have to be drilled to join everything up in the correct order, then you have to make the control valve. Of course you have to seal off the other end of the cylinder and put a stuffing gland in there, and because of the length of the stuffing gland, the length of the engine has to be increased, as well as the piston rod.

So maybe about four times the work of a single acting one.

John

[HS93]

As your a fan of mamod are the train piston units double acting, if so how about a conversion to them , that would be different and reverse and a bit more power, and still Mamod

Peter

[Stilldrillin]

By `ek you lot. Steady on! 

The original aim of the project was to make something the same, but different...... Better, smoother, quieter. 

There is a little more to come re this engine, when I get the time to write it. 

I`ve now got a long term aim of 4 engines. Single, double, triple, quobble. All recogniseably SE3 Mamod.

The 4 has been mocked up, but no further.......






David D

[Darren]

By ek David, you're really going for it there, that looks great, any chance of some pics of that manifold? 

[Stilldrillin]

There you go, Darren!

Just added a couple of 1/4" rods for a bit of weight.....



David D

[Darren]

Thanks David, I was wondering what the bars where for....

[John Hill]

Nice work David

It is a pity about the condensate and I realise it would not be a good idea to build an injector to put that oil contaminated water back in the boiler, so scrub that idea.

But how about reheating the steam/water before sending it out the funnel?  I am thinking there may be room to route the exhaust pipes through the 'firebox'?

[NickG]

Yes, it would be a tricky to make it run in reverse. Flicking it backwards won't work, you would need some sort of valve that would swap the inlet and exhaust port on all 3 cylinders! On the Mamod traction engines they have a lever and 3 ports instead of two. The lever sort of shifts the whole cylinder up to become aligned with either the middle and bottom or middle and top ports for each direction. So the middle port is a sort of common exhaust port! Not sure exactly how it moves the cylinder whilst keeping the pivot bearing still, it must be some sort of primitive cam arrangement I think.

To make it double acting would require a full redesign as John said! In fact, you might as well start from scratch as the port faces don't go down to the bottom of the cylinder etc.  You might be able to keep the flywheel, cranks and main bearings, but unless you were going to have a very short stroke, bin the rest and start again!

[Stilldrillin]

Nice work David

It is a pity about the condensate and I realise it would not be a good idea to build an injector to put that oil contaminated water back in the boiler, so scrub that idea.

But how about reheating the steam/water before sending it out the funnel?  I am thinking there may be room to route the exhaust pipes through the 'firebox'?

John,
The condensate now drains out of the collector in the chimney base, into a collector tank.

Since installing the plastic pistons, it is clean enough to pour back into my boiler water bottle & re use again! 

More to follow........

David D

[John Hill]

John,
The condensate now drains out of the collector in the chimney base, into a collector tank.

Errr, that would be me again not paying attention in class!

[Bernd]

David,

Did I see a compressor from a refrigirator as an air supply to the engine?

They do make nice little quite compressors and vaccum pumps.

Bernd

[Stilldrillin]

David,

Did I see a compressor from a refrigirator as an air supply to the engine?

They do make nice little quite compressors and vaccum pumps.

Bernd

Yes Bernd,

That one is from a small  home dehumidifier.

It test runs all my engines, no problem. Usually.......

At first assembly of this present build, it couldn`t turn the engine over. 

Now it fairly flies! Proving the efficiency of each one of the improvements. 

David D

[shoey51]

I must have been sleeping to miss this thread
great job there David and beeing one that has actually seen your first engine I was mightily impressed.
 wont miss any more of these goings on thats for sure

cheers Graham

[Stilldrillin]

I must have been sleeping to miss this thread
great job there David and beeing one that has actually seen your first engine I was mightily impressed.
 wont miss any more of these goings on thats for sure

cheers Graham

Heyup Graham!

Thanks for that..... 

Looking forward to seeing you and Jilly, seeing it again....... 

David D

[Stilldrillin]

Continuing.......

As mentioned, I made up a set of plastic pistons..... You all know about them....... 

But, as I was installing them & reassembling the crankshaft, I noticed the loctite had let go in the centre crank. 

Hmmmmm......

Cleaned up, restuck, rebuilt, reset......




4 hours running at Lincoln..... Bit of a clonk, again! Whenever no1 cylinder "fires".
The loctite`s gone again! 

Holding onto no1 & no3, the crank will twist!

Also the centre crank can be moved up / down. Too much bearing play..... But, it is only a toy!

Nowt for it, but to rebush the mains..... 

I line drilled the first 3 bearings 13/64", but the drill was too short to reach no4......




Sooo..... I drilled a hole through a bolt & locknutted it to the drill, allowing me to hand drill through no4.




Turned some brass bushes .1" long & loctited into place.




All nicely in line. 




The top piece of crankshaft is original, & worn.
I was surprised at the wear on the other 1/2 crankshaft, a piece of silver steel installed last year, worn -.003" or so! 




Nice shiney new silver steel shafts.




Running in..... No wobble..... No clonk..... Fingers crossed.....



Well I`ve ONLY got to sort the burner now......... 


Incidentally....... I`ve had another idea about those pistons! 

To be continued......

[sbwhart]

Nice fix David look forward to next instalment

Stew

[bogstandard]

David,

I think I mentioned to you that the pistons needed to be threaded onto the rod before being stuck with Loctite. PTFE is too slick to be held in a hole by itself.

John

[Stilldrillin]

David,

I think I mentioned to you that the pistons needed to be threaded onto the rod before being stuck with Loctite. PTFE is too slick to be held in a hole by itself.

John

Sorry John,

I missed posting this pic on "Stainless Pistons".....




Finished at 5/16" dia o/d. They are screwed 1/8"bsw & loctited......

My present thoughts are to screw the original brass piston 1/4bsw.

Less volume of ptfe. Less expansion......

David D