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Author Topic: Model 6 kick starter  (Read 5714 times)

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Jim Barbour

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Re: Model 6 kick starter
« Reply #21 on: December 03, 2014, 11:05:26 AM »
Thanks very much for that, I will be back in the workshop next week and will consider the best options (allowing for ability and materials!) I will report back when I have finished it for future reference.
Jim

phutton

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Re: Model 6 kick starter
« Reply #20 on: December 01, 2014, 05:39:59 PM »
I have called in the big guns! This is a comment from Malcolm Webster.

"I have looked at a few of these and I think that they were just made as an interference fit, i.e. they were machined close tolerance and pressed together, I guess this is satisfactory as there are no loads acting to pull them apart - just the oposite.
When I have made these myself I have actually brazed the parts together - two methods. 
1. Using Sif bronze which melts about 875 degrees , braze the parts and whilst still red hot quench in water to harden followed by cleaning up and reheating to a straw colour to temper the hardness.
2. using silver solder the parts can be hardened first and then silver soldered at about 610 degrees.

I guess you could even use soft solder as there is no real load on the joint."

The thought also crossed my mind that you would not want to use silver steel for the knob as it is very difficult to machine and get a good surface finish - it is a bearing after all! You could use EN8M and direct harden it by plunging in water at red heat (Lucas wiper shafts were done that way, or use a low carbon steel (EN1A) and case harden it with Kasenit.

Jim Barbour

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Re: Model 6 kick starter
« Reply #19 on: November 28, 2014, 08:04:28 PM »
Thanks for that Graham, threaded and Loctite after hardening it is then.
Jim.

shorrog

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Re: Model 6 kick starter
« Reply #18 on: November 27, 2014, 10:53:36 PM »
Hi Jim
The problem is that to harden the silver steel you need to get it red hot. Then to temper just a light straw colour of 150 to 300C. If you harden after silver soldering you will melt the silver solder and the end may drop off when you plunge the assembly into water, if you harden before silver solder the act of silver soldering will I think  largely destroy the hardening.

When all is said and done there are very few forces acting on the rod, it is simply pressing the clutch plate. I am fairly sure that you could screw the rod tight into a hardend end and just locktight to ensure it does not screw off.

The alternative of simply forcing the rod into the end when the end is red hot and then hardening, by plunging into water followed by tempering should also work.
Graham

Jim Barbour

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Re: Model 6 kick starter
« Reply #17 on: November 27, 2014, 08:10:35 PM »
How's this for a plan? If I turn off the original knob on the lathe (after measuring of course), turn up a new one then silver solder it on to the original rod, then temper the knob end (sounds painful) does that work?

shorrog

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Re: Model 6 kick starter
« Reply #16 on: November 26, 2014, 09:43:09 AM »
I recon that might be tricky. To temper the silver steel you need a temp between 150-300°C. But the silver solder needs 600 to 700°C. So if you silver solder after tempering you will soften the silver steel considerably.

phutton

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Re: Model 6 kick starter
« Reply #15 on: November 25, 2014, 11:05:13 PM »
It's too late at night! Thinking again, silver solder is the most likely as brazing temp is likely to soften the knob.

phutton

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Re: Model 6 kick starter
« Reply #14 on: November 25, 2014, 11:03:25 PM »
Since Marstons were very good at the process, I suspect the knob may well have been brazed on, or possibly silver-soldered.

shorrog

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Re: Model 6 kick starter
« Reply #13 on: November 25, 2014, 04:40:06 PM »
I am not sure they are one piece. It would take a fair bit of manufacturing and waste a lot of material, is it not more likely that they are a really tight interference fit on the end of the rod.

Ps If you are still looking for one I could turn one up for you if you have a bit of silver steel the correct size.

Graham

wessex_man

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Re: Model 6 kick starter
« Reply #12 on: November 24, 2014, 07:31:25 PM »
I think the real ones are all one piece.

Jim Barbour

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Re: Model 6 kick starter
« Reply #11 on: November 20, 2014, 07:57:33 PM »
Does the knob screw on to the clutch thrust rod ?
Jim

wessex_man

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Re: Model 6 kick starter
« Reply #10 on: November 20, 2014, 06:27:11 PM »
Yes worn quite straight forward to make out of silver steel and harden. Someone (from memory) has also fitted a ball race replacement as their bearing part of the arm gets worn as well.

phutton

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Re: Model 6 kick starter
« Reply #9 on: November 19, 2014, 10:52:18 PM »
I think yours is worn Jim! It looks like it has gone through the case-hardened layer. A decent machine shop should be able to clean it up and re-harden, or make you a new one. Unless anyone out there has a spare...?

Paul

Jim Barbour

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Re: Model 6 kick starter
« Reply #8 on: November 19, 2014, 08:15:48 PM »
Thanks very much, that gives me something to work with. I don't suppose you know whether the clutch thrust rod knob has a groove for the ball bearings to run in or is mine just very worn? Jim.

wessex_man

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Re: Model 6 kick starter
« Reply #7 on: November 19, 2014, 07:19:26 PM »
Typically Sunbeam they used several kick start ratchet gears and springs. pictured below. The ones for earlier models are narrower for the brazed kickstart quadrants. The later ones wider for the detatchable loose tooth types.





I think the spring you want is like the one below. It appears to be made from approx 2mm dia wire (sorry don't know what the SWG is) and has a three coils with the ends ground flatish the OD is approx 35mm dia but must be loose enough so that it can compress into the groove. The one pictured was made by Martin Batbury. I am not sure that he is making springs much these days but may have some in stock. It's worth a try.



Hope this helps WM
« Last Edit: November 19, 2014, 07:44:37 PM by wessex_man »