Engine sprocket and shock absorber

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bevanclark
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Engine sprocket and shock absorber

Postby bevanclark » Sun Apr 21, 2019 6:05 am

Hi folks,
I managed to buy a 23 tooth sprocket to replace the 19 tooth one on my 1950 VB; but having dissembled the primary side, I find that the lobe profile is not the same, so it doesn't match up with the shock absorber. See attached photos - current 19 tooth one is shown first. The sprocket i.d.s are the same, but the lobe on the new one is thinner (as well as being a different profile).
My question is: were there two different sprocket/absorber lobe profiles, or is the one I have bought not actually an Ariel sprocket ?
Cheers,
Bevan
ps I might have just found the explanation from the Draganfly website"
"Shock Absorber
The later type absorber assembly with a wider face cam that was fitted after 1945 can be fitted to 1930 and later models."
Maybe I've bought a pre-1945 sprocket ??
Attachments
19 tooth sprocket with shock absorber.jpg
23 tooth sprocket with shock absorber.jpg

nevhunter
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Re: Engine sprocket and shock absorber

Postby nevhunter » Sun Apr 21, 2019 9:26 am

That's how they are. If they fitted face to face the action would be less gradual. Nev

bevanclark
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Re: Engine sprocket and shock absorber

Postby bevanclark » Sun Apr 21, 2019 10:52 am

Hi Nev,
I acknowledge my inexperience with Ariels, but i cannot understand how the new sprocket could work with my current sliding member. Could you please take a look at this little video clip:
https://youtu.be/LC15GBjO9u4
Cheers,
Bevan

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Re: Engine sprocket and shock absorber

Postby john.mitchell » Sun Apr 21, 2019 12:23 pm

Unfortunately where I am living currently I can't check physically. However there were two sliding members - from 1930 onwards designated 1272-30 and after 1941 1272-41. I wonder if you have a mismatch

John
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paul.jameson
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Re: Engine sprocket and shock absorber

Postby paul.jameson » Sun Apr 21, 2019 8:25 pm

There are indeed two widths of the cush drive face. The later one is the one shown in your upper photo which is the more common version. The earlier narrow type is the sprocket in the lower photo. This early version uses a different sliding member which lives in a cup and is rarely used these days although I did sell a few of the early type sliding members when I was Singles Spares Organiser many years ago. I probably sold 2 or 3 in total compared with 30 or so of the later type.

The good news is that you can use the early type sprocket with the later type sliding member. You will only have half the contact area so it will wear out at least twice as fast but it will work perfectly well until it does wear out. Judging by quite a number of sprockets and sliding members I have seen over the years, use of the narrow contact area sprocket with the wide contact area sliding member has been a common practice in the past.
Paul Jameson
36 4G, 37 VH, 54 KH(A), 75 Healey 1000/4, 52/53 ex ISDT KHA (project).
Former Machine Registrar & Archivist, General Secretary and Single Spares Organiser (over a 25 year period).
Now Archivist once more - but not Machine Registrar.

bevanclark
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Re: Engine sprocket and shock absorber

Postby bevanclark » Sun Apr 21, 2019 10:13 pm

Hi John and Paul,
Thanks for the reassurance - I bow to your greater knowledge :).
As you can see from that video clip, the action of the original is so smooth with nearly full contact of the working surfaces, while the fit with the older style sprocket is so poor, that it made me really anxious that I'd cause some metal shredding disaster if I fitted it.
Will give it a go once I've got hold of a longer primary chain.
Thanks very much,
Bevan


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