Stuart? MTB 1M

[DiogenesParticipant @diogenes]

Ha, no, no doubt about the strength, was thinking that the ‘as machined’ finish look pretty good – I was fishing because  I’ve had some hot-rolled that always seemed to be a bit raggy however you cut it: maybe I need to replace tips more often..😊

I think 24T is reassuring say for overhung cranks in sporty CI aero engines where the stresses and strains of a very manly punch are concentrated right on the neck of the crank and the pin..

[JasonB]

On JasonB Said:

On Howard Lewis Said:

 

Another method, for anyone who wants to experiment would be a slide valve operated by a pivoted lever and a face cam on the crankshaft./

 

See my reply above yours and the link to the original No1 MTB with it’s face cam.

Westbury did the Gemini high speed steam engine which had a gear driven rotary valve, Gray Meek did his own designs inspired by the Gemini which use a toothed belt.

ETW used to do a column in ME called ‘Utility Steam Engines’. One of them was a single acting twin with a bevel gear drive to a vertical shaft between the cylinders and a flat rotary valve on top, bit like the 3 cylinder radial whose name escapes me.

Cylindrical rotary valves seem to be the holy grail of steam engines, the Paget  loco built by the Midland Railway, wasn’t all that successful. If you make the clearance twixt valve and sleeve too small it seizes up, too big and it leaks like a sieve. Gray is clearly one of those demi-gods who can achieve such accuracy. I once worked with a chap who had worked for Roland? Cross on rotary valve IC engines. He reckoned when they got the oil consumption lower than the fuel consumption they were doing well.

Bill Hall was working on a vee 4 with semi rotary valve similar to Corliss when he died, somewhat easier to get it to seal.

[JasonBModerator @jasonb]

I’ll have to look that one out but can’t see anything obvious at the moment. The radial was “cygnet Royal”

[JasonBModerator @jasonb]

Unable to find an enclosed twin with any form or Rotary Valve by Westbury.

 

 

I did not take any photos of the valve, its nut or rod as they are nothing special and just like you find on any slide valve steam engine. The Scotch yoke that drives the valve rod was machined onto the end of some round bar, sawn off and then milled down to the final 5mm thickness before drilling and tapping for the valve rod.

As the eccentric drive pin has quite a short throw and would clash with the vertical shaft I chose to turn the pin and disc as one piece and then Loctite the 4mm silver steel shaft into a shallow hole rather than inserting one then trying to drill and ream an overlapping hole.

The photos of original engines seem to all show them assembled with screws so I machined up a batch of Filister nead ones in M3 and M2.5 which completed all the machining save for a couple of plugs for the drain and valve chest oil hole and a capped tube to fill the crankcase with oil. The Aluminium crankcase halves were bead blasted and the “cast” surfaces of the iron parts given a coat of paint.

I only assembled the engine with a couple of drops of oil on the moving parts rather than filling the sump with oil so did not have the splash lubrication for test running. Also with no form of lubricator on the inlet I did not want to push my luck too far. But with a larger diameter inlet tube and 45psi on the regulator I was happy to stop the test at 3000rpm and expect the engine could go faster as I did not have the flow regulator fully open. Sorry the Tacho video did not come out but you should get an idea by the noise at the end of the video.

[KEITH BEAUMONTParticipant @keithbeaumont45476]

Another beautiful piece of work, Jason. Are you doing the bead blasting yourself?

Keith.

[Howard LewisParticipant @howardlewis46836]

As Keith says,

Superb work by Jason.

An interesting mod to use a Scotch Yoke for the valve gear on the twin cylinder Stuart?

Howard

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