Member postings for John Bramwell

Yes! There was just enough tread protruding to turn it out. Then repaired cylinder end gasket and valve chest gasket and she ran with air from an old fridge compressor. But only when the air hose was connected to the cyclinder not the boiler. then I connected the boiler and fired it up with the spirits and it started to run but dithered backward and forwards. It seemed to have enought power but maybe steam was escaping past the piston or to both ports at the same time and then forcing it to go change direction. Is this common?.

Well, as Howard said" things may not be as bad as i feared". I connected an old fridge compressor to the bock when removed from the loco to see it better. It run nicely although there were serious leaks from the end of cylinder gasket and joiint between the vslve chest and block. The cylindrer end cover has one of it two screws sheared off. But there is spce to drill 2 more. Im optimisti now. Where do members buy 1/16" screws and a tap? .

Thanks Howard and Nigel, that most encouraging. I do have an old Lorche and Schmidt lathe so i really should break the ice. Nothing to loose really as i woulc be ma!ing new parts not altering the old ones.

well the glands dont leak but i think the problem is the valve and the piston is worn out. Also the loco has done some miles as the crank/big end and eccentric have play in them probably enough to effect the timing. Do you know anyone who offers an overhaul service? It appears to be well made so worth reconditioning.

Thanks Jeoff and Jason. I guess it also depends on the rate at which the boiler can produce the steam.

Hello

I have draw a twin cylinder double acting oscillating engine to pull a toy train on the flat. With a 2mm ports positioned so that they fully coincide at mid stroke (90 deg) there is a 33 deg delay before commencement of opening. Should that be reduced by elongating the cylinder port? I built one without such elongation but that did not have any load and had a heavy flywheel. (FYI 8mm bores 20mm strokes). cheers John

That sounds do-able. What about the stuff that looks like horse hair? Good for threaded maleable iron but might expand too much and impead the shaft.

You are correct, it is a knurled spigot with the glan in side. better photo to come. thanks.

Please look at this photo of an engine out of my Archangel Snowdon Ranger whi h wont run. It just leaks the steam out the rods. There are threaded faucets so i think there should be glands there. Can you tell me where i can get some or what thread it might be? The outside diameter is about 4.85mm and it looks like 5 threads in 1/10" .

Nigel has dubbed my timing wheel "the Bramwell gear" which is quite a coincidence because i have a book entitled Railways and Locomotives, lectures selivered at the school of military engineering at chatham in 1877 by John Wolf Barry and Frederick J Bramwell.! In it there are many beatifully drawings including three types of valve linkage; ordinary, reverse radial and straight. Here is a photo of the ordinary linkage

Nigel. The LBSC Juliet might be good for me, It has the main cylinder on the outside of one continuous frame member and the valves on the inside. I can fit my cylinders on the inside and valves on the outside for ease of access but the cranks and arms underneath might make fitting the burners tricky.

Hello Duncan

Yes 33 was an error. But on that, should the wheel sit square on the track with a the flange on the inside?

Could you explain why i need two shafts from the axle to the layshaft? is that to put the two engines ot of phase?

Love your chain driven layshaft and i can imagine the reaction to it. I had a 1970 BMW SOHC with a cam drive chain and oil pressure tenioner. No changing belts. Did you make the sprokets?

My goal is not to build a mini version of an actual loco or to design an engine that is different for the sake of it, but to design an engine that is simple and easy to make to entain the kids. john

I have added colour for some clarity. There is also a layout. The two blocks are close together so should i combine them?

Nigel. many thanks, i would go with the potmill but except that i want the valve chamber above the main chamber to save space so i can have this on bothsides of the loco. Ive got O gauge track.

I said that my timing wheel 2 reduces the main piston stroke length to valve stroke length

You say "'2) With respect I am puzzled by that. The valve travel is usually less than the (power) piston stroke.

But if you look at the drawing, the valve arm pivot is closer to the centre than the driving pivot so there is no puzzel. main piston stroke 19mm valve 10mm. the crank piece is above the driving arm pivot and the valve arm piivot is on top of the crank piece.

What is a good bore and stroke for an O gauge loco on flat track? Do slide valve leak less than piston valves made to the same tolerances?

It might help if i give you the loco layout as im sure there will be more trap for young players.

Cheers John

Dave, you mean lime this? See revised plan. John

Thanks Redsetter for you promt comments. You may not have been able to read the note under the timing wheel "crank sits 10mm out from wheel"That allows the driving arm to go under the the crank and not hit it. The pivot for the valve arm is above the crank. Another clarification the crank is one piece with the drive pin.to keep the valve arm pivot concentric

The "future'' fine tuning I refered to consists an outer disc which can rotate wrt the back disc. The front disc would be screwed to the back through slots. Bit like the Bosch VE injection pump on my car. But ill redo it with an eccentric and see how it looks The driving arm would go over the top of it. Stay tuned for revision..

Gentlemen

Ive replaced that silly pendulum with z timing wheel driven by the flywheel This does 4 things 1. Puts horozontal movement in line with valve chamber, 2 reduces main piston stroke length to valve stroke length. 3 phases the timing to open a TDC. 4 Alows for future fine tuning of timing. I didnt copy the Caladonian becausd i like needle rollers over slots and eccentrics. Your comments please and many thanks for previos help.

Brian et al

Didnt have much luck with Dockstader but found J,Y Jins computor simulations (https://www.youtube.com/watch?v=ed3vMFQNzCc) Timing realtionship between valve sheet and main piston of a steam. And his cylinder is the same as mine so this supports Redsitters advice. Please have a look at this and tell me what you think. I still think my design will run because the steam will push the piston in the right directiion which is the absolute basics. And if i build it and it doesnt work then it is not too hard to change it to put a crank in the wheel axle at 90 deg to drive an adjustable eccentric.

Ok. Here is the basic design of the pendulum vale actuator. Some of you thought that there was no lead but as you can see it has a modified valve piston and cylinder which is full open at TDC. So cracks open at 90 deg BTDC. The valve chamber bolts onto the power chamber. The shafts are conneted to the pendulum by slots to allow for vertiacal displacement. Will it work? John