68 replies to this topic

[totalshell]

jump into a fantic forum where nikasilling is common, as i remember when i had mine done only two places in the uk any good with the best being in the south west..

[charlie prescott]

Hi Guy's

OK,
Got a lump of Jelutong,( Wood from Malaysia) and have sourced some 3mm Birch ply too model the fins on the wooden pattern. And have been in touch with the "Monkey on my shoulder"! (sorry Paulie) and he has told me he has an old book in his extensive library, on casting practices, he also said I need a Pattern Makers Rule, or a "Shrink rule" as they are called. He has an old Rabone catalog with one in but said it was 2 shillings and 6d. so the price was well out of date. The only one I can find, is in the States, but it would be wouldn't it, as them boys are into every thing. Paulie said, don't forget if you intend to fit a dry sand core into the mould you will have to incorporate prints into the pattern to hold this. Yea OK Boy, I said. Looks like I am getting into a whole new world of "Foundry Speak". Looking like fun though.

Regards Charlie.

[B40RT]

charlie prescott, on Jan 5 2010, 05:48 PM, said:

Hi Guy's

OK,
Got a lump of Jelutong,( Wood from Malaysia) and have sourced some 3mm Birch ply too model the fins on the wooden pattern. And have been in touch with the "Monkey on my shoulder"! (sorry Paulie) and he has told me he has an old book in his extensive library, on casting practices, he also said I need a Pattern Makers Rule, or a "Shrink rule" as they are called. He has an old Rabone catalog with one in but said it was 2 shillings and 6d. so the price was well out of date. The only one I can find, is in the States, but it would be wouldn't it, as them boys are into every thing. Paulie said, don't forget if you intend to fit a dry sand core into the mould you will have to incorporate prints into the pattern to hold this. Yea OK Boy, I said. Looks like I am getting into a whole new world of "Foundry Speak". Looking like fun though.

Regards Charlie.

Love to see some pictures as you progress.

Ross

[charlie prescott]

Hi Guy's,

Pat Slinn,
Just e-mailed me with this information, I'm sure he won't mind me re publishing it on here. He also said,did I think the Scottish Pre65 committee, would allow cast in push rod tunnels on A C15? You tell me.
Here is Pats e-mail.

Hi Charlie,

Part of my "general" engineering training whilst a apprentice at BSA was spending time in the pattern making shop and casting prototype castings. BSA management in their infinite wisdom decided to close down the pattern shop and have all casting out sourced. another lost skill. Apart from sending young apprentices for "long waits" and "left handed screwdrivers" some of us were tricked into using "shrink" rules for general use!!!!. Causing great fun amongst the older craftsmen. If anybody tried that to day it would probably be a violation of something or other. As you progress with the patterns perhaps you could post them on trials central, that would make a very interesting post. Funny you should mention Jelutong a friend of mine only showed me a piece that he had in his garage, his father was a pattern maker. Pat.
Yes Pat I will post some photos as I progress.
Regards Charlie.

[kev99]

hi charlie, how did you widen the cub swing arm without cutting it
was thinking of doing one myself. cheers kev

[charlie prescott]

Hi Guy's.

Hi Kev.

Right, first you need a surface table, or a flat surface of some kind. And also the use of a set of gas bottles.
Now, as you look at the swinging arm from the back, the right hand leg is straight? Yes? now this is the side you modify. you really want two angle brackets with holes in to be able to bolt the pivot spindle to these brackets , and then clamp them to the table, if you see where I am coming from. Now, If you look at the casting the tubes are brazed into, you will see that the left one (from the Back) points out at a slight angle, this is the profile you need for the other side. So you really need some one with gentle hands to put outward pressure on the right hand leg,while you heat the casting diagonally across the corner until it is about cherry red, your other pair of hands should then feel the leg moving slightly, now just play the heat gently on to the casting until it resembles the other side, (DO NOT) Apply to much heat or the casting will crack. The right hand leg should now be out at an angle. Let the casting cool. Now measure and mark up where you need to bend the leg tube to match the other. Again apply heat to the leg tube at the point where it needs to be bent. gently pull this back when hot, too the profile of the left one, and until the back dropouts are parallel.If you string a center line from the front you should now have a measurement from this center line on both side of the center of about 3. 7/16" . When cool you can cold set and true on the face table. After some time I also decided to lengthen the back spindle plates by 1", then filling in the same amount of spindle hole at the front. Should I have made or bought a newly manufactered one? But it was fun.

This is something like it should look, Picture Greystone.

Attached Images

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Edited by charlie prescott, 12 January 2010 - 04:23 PM.

[kev99]

hi charlie,thankyou for your reply but now i am confused!!!! the 2 swing arms that i have both look like the pic and measure 150mm across the inside back edge. was this a factory part or would someone have kindly widened them for me. will have to dig in the garage and see if i have a striat one. but it looks like i have saved some gas,just slipped it over a 400 back wheel and it looks to have good clearance.. thank you again for your help ... kev

[charlie prescott]

Hi Guy's.

Hi Kev.
Good news then, all you need do is lengthen the plates at the wheel spindle end by 1" to be a good job. The arms you have could be BSA Bantam D7 I think. Do they measure 6 3/4" ish, between plates? I'm here to be corrected as I have never used them, perhaps I should have? To any one who carries out similar mods ,Don't forget you need to widen the top damper mounts to the same width as the swinging arm, or use Trikshocks, or any units with Rose joints.

Regards Charlie.

[B40RT]

charlie prescott, on Jan 12 2010, 06:39 PM, said:

Hi Guy's.

Hi Kev.
Good news then, all you need do is lengthen the plates at the wheel spindle end by 1" to be a good job. The arms you have could be BSA Bantam D7 I think. Do they measure 6 3/4" ish, between plates? I'm here to be corrected as I have never used them, perhaps I should have? To any one who carries out similar mods ,Don't forget you need to widen the top damper mounts to the same width as the swinging arm, or use Trikshocks, or any units with Rose joints.

Regards Charlie.

Hi Charlie

I take it that your background is engineering, interesting getting the hands on experience/info that you obviously have. (and Wayne)

[charlie prescott]

Hi Guy's,
Just been doing a bit more research on BSA and came up with this GEM http://www.babelgum....jeff-smith.html. Now sit back and enjoy a piece of history,filled with information.Brilliant. Bruce Cox ! Is it the Bruce Cox I used to know way back,from Banbury?

Regards Charlie.

[2fargone]

Thanks for that link Charlie, very interesting.

[kev99]

hi all. Thanks charie. i did the mod on swing arm length by 1 inch . cut the full spingle adjuster off and had new ones profile cut plus 1 inch to the front this way no need to fill and it thought 1 weld rather than 2 would be stronger { could be wrong} but without the chain tensioner lugs. i drilled and then welded pins for snail cams. do you prefer powder coating or good old paint and laqure? kev

[charlie prescott]

Hi Guy's
Hi Kev,
Yes as long as the weld is good there should be no problem, you could always go over the top and stress relieve it, by reheating, then polish the plates up and temper them to the correct colour, cool in oil.
I should use it for a while,and make sure it is OK before powder coating, but that is the way to go. PS I should leave the welds as they are and not grind them down.

Regards Charlie.

[kev99]

hi all, Thanks again charlie as you may have worked out i am a bit of a novice at this game ,but all the help on here is wonderfull
so you may have other questions along the way !! hope you dont mind ..kev

[charlie prescott]

Hi Guy's.
Hi Kev.
Here to help if I can, Many have helped me with information, here on TC, And I thank them all for it.

Regards Charlie.