Author Topic: Bike Timing Sprocket.  (Read 17930 times)

Offline Zadig

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Bike Timing Sprocket.
« on: April 07, 2015, 09:02:15 AM »
A friend of mine asked me if I would make him a timing sprocket for his classic bike. The guy is one of the most gifted engineers I have come across but he was struggling to get a fabricated sprocket to run true enough. I tend to post over a few days so more tomorrow.










Offline Brass_Machine

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Re: Bike Timing Sprocket.
« Reply #1 on: April 07, 2015, 11:54:20 AM »
What kind of bike?

Eric
Science is fun.

We're all mad here. I'm mad. You're mad.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #2 on: April 07, 2015, 12:49:43 PM »
It's for an OK Supreme as far as I know.

Offline Brass_Machine

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Re: Bike Timing Sprocket.
« Reply #3 on: April 07, 2015, 01:20:45 PM »
Nice. Do you plan to treat the steel when you are finished?
Science is fun.

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Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #4 on: April 07, 2015, 03:29:49 PM »
No, the steel is EN19T, a chrome alloy, which is fairly tough stuff and already in a treated state. I picked up 7mtrs of it at an auction a wee while back.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #5 on: April 08, 2015, 02:10:05 AM »







Offline Lykle

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Re: Bike Timing Sprocket.
« Reply #6 on: April 08, 2015, 03:35:42 AM »
7 Meters! Heavy chunk of steel. Wow.

Things are progressing nicely by the look of it. Pretty soon you will hit the tricky parts. Looking forward to that.
Lykle

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Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #7 on: April 08, 2015, 04:02:00 AM »
Thanks Lykle,

Thankfully, the steel was already cut for a job and came in 700mm lengths. There was some lovely large diameter material there that day, that went through cheap. I had no idea what the spec of the steel I bid for was, it was just one of those pot luck gambles you take from time to time. I was hoping for a good, fairly free machining case hardening steel, but got this instead. Ironically, I have just got through the last bits of a load of 100mm EN24T which was purchased at another auction years ago. I made a set of powered rolls with most of it and will probably do the same with this stuff. As it turns out, this material is ideal for tooling and gears which crop up fairly often.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #8 on: April 09, 2015, 01:26:39 AM »







Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #9 on: April 10, 2015, 01:40:30 AM »














Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #10 on: April 11, 2015, 01:40:08 AM »







Offline mexican jon

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Re: Bike Timing Sprocket.
« Reply #11 on: April 11, 2015, 04:02:57 AM »
Nice work  :thumbup: I have a couple of questions  :lol: why didn't you bore to size when you had it in the 3 jaw chuck that most of the machining was done ? What was the logic in using a faceplate rather than a 4 jaw chuck ?
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #12 on: April 11, 2015, 05:54:18 AM »
Firstly, thanks for the thumbs up, glad it amused you.

I wanted a good fit on the taper. If I had done as you said and cut the taper with the op in the first instance, I would have had to have left the large boss on to hold the blank to machine the reverse side. This would then have necessitated a further op to reduce the boss to the finished size. If you are suggesting that the whole of the front face could have been machined in one setup, then there would have been a danger of crushing the taper when machining the obverse side, plus this extra step would negate any advantage you were trying to gain.

Cutting the taper using the topslide was also made easier because the reverse side has the recess. It's quite a deep hole for a small boring tool, so any advantage in chip clearance because of the through hole, on this tough alloy steel was welcome. It gave me the advantage of not having to drill deeper than was necessary to give clearance for the taper thread, thereby potentially ruining the end of the remaining stock.

I see no logic in holding it in a four jaw to machine the rear. Clocking the back side of it would have been awkward to say the least. Then there are the holding marks it would leave on the diameter. The tooth thickness is only .188" thick, which would have needed some holding force in the four jaw.


You may think differently, but like all things in this game, you do what suits you.




Offline mexican jon

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Re: Bike Timing Sprocket.
« Reply #13 on: April 11, 2015, 08:50:23 AM »
Firstly I was laughing at myself  :scratch: as I knew there was a perfectly logical reason you had done what you had done  :clap: I guess I should have studied the pictures more and realised that the spocket was going on to a taper  :doh:

It was just as I was thinking of the questions I was giggling thinking when I read the answers  " Jon you should have realised that"  :) :)
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #14 on: April 11, 2015, 09:28:07 AM »
It was a fair question and I had to think back as to why I did it that way. If you have the patience there is nearly always a few ways to get the job done. A four jaw could have been used, but setting it up would have taken a fair amount of time in comparison to the way it was done.

Thanks again for the comment, I'm still new here and finding my way around.


Offline Manxmodder

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Re: Bike Timing Sprocket.
« Reply #15 on: April 11, 2015, 11:41:32 AM »
Another advantage of clamping flat to a faceplate is that it tends to reduce any resonant frequency being set up in the component itself. This method of mounting provides a damping effect and helps to further reduce the likelihood of chatter marks in a critical bore where conditions are fairly borderline to begin with whereas the relatively small contact area of a 4 jaw doesn't provide near as much damping effect.

Nice job so far Zadig  :clap: :clap:.....OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline Ginger Nut

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Re: Bike Timing Sprocket.
« Reply #16 on: April 11, 2015, 11:41:58 PM »
 :thumbup: :thumbup:

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #17 on: April 12, 2015, 02:21:45 AM »
Thanks OZ. Nice point about the damping.

Cheers Ginger.

The suds was a bit gruesome, I used some neat cutting oil and a brush in the end.













Offline awemawson

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Re: Bike Timing Sprocket.
« Reply #18 on: April 12, 2015, 02:49:17 AM »
Very nice.  :bow:

Are you going to black it?
Andrew Mawson
East Sussex

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #19 on: April 12, 2015, 03:09:31 AM »
No I didn't Andrew, I'll leave that upto the guy himself. It's his field, restoration, and he will have far more idea than I have about these things. It would have looked good though.

BTW, I like your idea of Sterling board for flooring. My concrete floor was put down in the pouring rain and powders up something terrible. I've been giving it some thought over the years but never gave OSB a thought. Just wanted to show my appreciation and say thanks.


Offline awemawson

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Re: Bike Timing Sprocket.
« Reply #20 on: April 12, 2015, 03:26:23 AM »
OSB has worked well for me over the years - I have a patch in my present workshop between two desks where my swivle chair runs and it's in dire need of re-painting, but apart from that it's stood up to wear very well, and is not too bad to stand on. Another advantage is that dropped tools don't chip!
Andrew Mawson
East Sussex

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #21 on: April 12, 2015, 03:55:22 AM »
I do tend to drop a lot of tools or more often a particularly nice piece of work. I often think to myself that it's a good job my balls are in a bag.

Offline mexican jon

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Re: Bike Timing Sprocket.
« Reply #22 on: April 12, 2015, 06:57:48 AM »
Cracking finished sprocket  :bow: :bow: :bow: :bow:

Here goes for another question  :doh: How did you index the spacing, or was it done on a cnc mill?
People say you only live once ! I say thank F@*K can't afford to do it twice.

Offline Zadig

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Re: Bike Timing Sprocket.
« Reply #23 on: April 12, 2015, 07:16:36 AM »
Thanks Jon.

I have to admit I cheated and used a CNC mill.

Offline vintageandclassicrepairs

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Re: Bike Timing Sprocket.
« Reply #24 on: April 12, 2015, 06:20:41 PM »
Hi Zadig,
Nice work on the sprocket :clap:
I am puzzled about the OK Supreme that its intended for ?
I know they made the ohc lighthouse model but cannot place a model with chain driven cam?
Could you ask the owner for some further information or a photo?
BTY I have a little 285cc side valve model from 1932 + a 36/7 JAP 250ov engine made and badged for OK
It even has "OK" cast into the head and cylinder !!

Regards
John