Author Topic: decompressor linking  (Read 421 times)

Online RDfella

  • Wise & Enlightened
  • *
  • Join Date: Aug 2017
  • Posts: 1285
  • Karma: 10
Re: decompressor linking
« Reply #15 on: 01.05. 2021 12:29 »
Recognise that description, Neil. I'd already dismantled the starter, wrapped the parts up and put them in a box. Having previously explored all possibilities I am aware of (sprag clutch, worm drive, crossed helixes, inertia bendix, inertia bevels and many others) before settling on a ratchet, I was convinced I'd reached the end of the road. I don't give up easily, but I also accept sometimes one has to face the fact what one is trying to achive ain't going to work.
And that's where I was until my son came across this American manufacturer of sprag clutches where I, for the first time, learnt that the max revs specified for one-way (sprag) bearings probably didn't apply to this particular usage. And so the reprieve, but we really are in the last chance saloon - if this doesn't work I have no other options. Riding a bike that you know you can't re-start if it stalls kinda puts one off using it, hence my recognising that without a starter it would just become an ornament at the rear of the bike shed.
And so another few weeks delay whilst waiting for parts. I'm using that time beefing up the starter casing where it mounts on the engine. It was flexure there whilst attempting an engine start which caused me to abandon the attempt. And thanks to members whose encouragement has helped keep me going.   
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online Greybeard

  • Jack of all trades; master of none.
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 6996
  • Karma: 38
Re: decompressor linking
« Reply #16 on: 01.05. 2021 16:30 »
What about starting the engine with a shotgun cartridge like those early single cylinder tractors?

https://youtu.be/vb0-br7hTw0

Online RDfella

  • Wise & Enlightened
  • *
  • Join Date: Aug 2017
  • Posts: 1285
  • Karma: 10
Re: decompressor linking
« Reply #17 on: 01.05. 2021 17:23 »
I actually considered that. Used to be used on tractors as well as aircraft.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online Bsareg

  • Valued Contributor
  • ****
  • Join Date: Mar 2016
  • Posts: 329
  • Karma: 2
Re: decompressor linking
« Reply #18 on: 01.05. 2021 19:17 »
If you stalled at lights in a city, just imagine the reaction of old bill when you banged in a cartridge!😁
C11,B40,B44 Victor,A10,RGS,M21,Rocket3,REBSA

Online RDfella

  • Wise & Enlightened
  • *
  • Join Date: Aug 2017
  • Posts: 1285
  • Karma: 10
Re: decompressor linking
« Reply #19 on: 15.05. 2021 20:58 »
Always been fascinated by cartridge starters, but probably not suitable in this instance. Pity. Tap it with a hammer and off you go. But think of the design nightmare - unlike some tractors where they simply discharged into the cylinder, there's quite a bit of engineering to convert an explosion into engagement and rotational energy - even more complex than internal combustion engines.
But the reason for this post is updating.
I have studied varius Vincent forums (being as their engines are similar to mine) and discovered a few interesting facts: firstly, Vincents have one decompression lever, the cable from which  enters the timing chest where it operates both decompressors (by lifting the exhaust cam followers as far as I can see). Secondly, some have tried those stand-alone units which one presses to decompress (and which hopefully return to normal upon engine start). Apparently not very successful as they don't flow enough gas with big cylinders. The cable-operated decompressors such as fitted to Enfields are apparently prone to carboning up.
But I did find an interesting possible solution, where one guy remarked that he used a bicycle lever to operate two decompressor cables. I've looked them up, and intend to purchase one in order to combine my decompressors into one lever. Here's hoping it will be suitable. In the meantime I've replaced the starter ratchet with a sprag clutch and am presently waiting on my alloy-welding pal to return the starter gearbox.
'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3525
  • Karma: 49
Re: decompressor linking
« Reply #20 on: 15.05. 2021 21:20 »
Hi RD
I'm sure Vincent's use a full size clutch lever for the decompressor
The mechanism inside the Vincent timing case involves "wheel spokes"  *eek*

John
1961 Super Rocket
1963 RGS (ongoing)