Author Topic: Automatic Timing Device Springs  (Read 1736 times)

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 4938
  • Karma: 46
Automatic Timing Device Springs
« on: 20.03. 2009 11:29 »
... why can't a person obtain, easily, new ATD springs? Is there a conspiracy? ... All springs are available if the spec is known..., so where's the list of spring specs for all the springs we need?

After completing timing, I was doing a last check of things before putting the outer cover back on. I gave the automatic timing device (ATD) a twist and the response was, shall we say, flaccid (Webster's definition #2). It did not return to the no-advance position even close. Someone had mentioned that SRM had springs and, in fact,they are in their on-line store. However, that was going to mean about a week before I could button-up. Deciding to see if I could do it myself,  I took my caliper, tension-force gage and one of the old springs to the local hardware store to see what they had. I stumbled on a reasonable facsimile in wire diameter, coil diameter and tension, so I decided it would be worthwhile trying to fashion a look-alike. Below are photos of the effort. In one photo, my two old springs at the top (one more stretched-out than the other) and the home-made spring at the bottom. In the other, the spring as bought from the store compared to one of the old springs.

It seems to work great and considering the similarity in spring tension, I am guessing I am farily close to tolerance. For fun and your amusement, I posted a little video on Youtube showing the action.

http://www.youtube.com/watch?v=rkEq3HYK6RA

I hope this is interesting, but I am not expecting the video to go viral.

Richard L.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Online groily

  • Wise & Enlightened
  • *
  • Join Date: Jul 2007
  • Posts: 1050
  • Karma: 17
    • www.brightsparkmagnetos.com
Re: Automatic Timing Device Springs
« Reply #1 on: 20.03. 2009 17:02 »
Well done Richard. Who knows if they're exactly correct, but better than flaccid definition Number Two which will leave your slow-running erratic for sure. When I was whining about lack of springs, I hadn't checked SRM for the ATD ones I must admit - but of course, as they recon the things, they must have them. I was thinking more of the little springs than do the same job in Lucas m/cycle distributors, as I need some for my single, the which I was unable to get from the normal sources I use. Don't need them for my A any more as I've gone aluminium with a manual mag end to suit.
But wouldn't a list of the specs be good so one could just order the things from whoever makes them? There must be one somewhere . . .
Bill

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 4938
  • Karma: 46
Re: Automatic Timing Device Springs
« Reply #2 on: 20.03. 2009 17:08 »
Yes, I am sure that list is in an old pile of papers in a remote corner of the 2nd basement in that building sitting on Armoury Rd., Small Heath, Birmingham, UK.
Plan on signing up for the world-wide 2017 DISTINGUISHED GENTLEMAN'S RIDE on September 30, 2018. Watch website at https://www.gentlemansride.com for details.

Offline dpaddock

  • NC, USA
  • Valued Contributor
  • ****
  • Join Date: Jul 2006
  • Posts: 429
  • Karma: 5
Re: Automatic Timing Device Springs
« Reply #3 on: 21.03. 2009 04:06 »
I bought a set from Klempf Cycles, Dodge City, Minnesota, in 2003.
mitch@klempfs.com
It's better for the ATD to advance more quickly than to stay partially or fully retarded. Given the mechanical slop in the typical ATD, who knows what sort of advance curve exists or how it's supposed to track?
Richard L has provided his typically good solution to our problems; thanks.
     David
David
'57 Spitfire