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Old 02-28-2007, 03:37 PM   #1
R-dubb OP
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Building custom G/S triple clamps

Need some advice and preferences.

I'm planning to design a CNC run of billet clamps to mount dirt forks on airheads. Ricky and I are working together on this and need three pair between us. I plan to offer some for sale to ADVriders as well. I'll solicit reservations when the design sorts out and costs are known.

Time to explore some issues and make decisions.

I'm partial to WP forks. We have two pair of 50mm Extremes, and two 43mm USD's. I know most folks would rather use 48's, so maybe there will be an easy way to use the same basic clamp to fit all three sizes. I'm pretty sure the hole centers are the same, assuming KTM axles (17, 20, 26mm) and wheels.

The biggest question is whether to use an upper and lower spacer to spread the clamps. The mounting surfaces on the USD forks allow some variation, but not enough to work with the head on a BMW frame. An upper spacer will effectively lower the front end by dropping the head. A lower one will be fork length neutral. The spacers would be designed to rotate with the clamp and use BMW head bearings with no welding.

A more radical alternative, which of course Ricky likes, is to redesign the steering head to use larger diameter stem and bigger bearings at the top and bottom. Essentially new bearing races would be welded to each end of the steering head. This approach would add rigidity (and stress to the frame) to the front end by spreading the bearing surfaces.

Another possibility would be to use a BMW stem with no head modification. The triple would then angle down from the center at the lower, and maybe upward on top, to widen the spread and clamp in the correct area on the fork. I fear that this method will be too costly both in terms of material thickness and complex machine work.

It is likely that the first method will be the simplest, but want to throw it out for discussion.

Any ideas on how to best accommodate more than one hole size for different size fork tubes? The magnums are 50 top and bottom. The 43's are something like 57 and 55mm. I haven't measured the 48's but my guess is the larger hole is 60mm. That translates to a variation of about 5mm in wall thickness. Sounds manageable with spacers or different bores within the same shape. I'm planning to use anywhere from a 40 - 50mm offset on the clamps. This will assure that the resulting trail does not exceed stock figures for the R80. I'd like to bring it down to something in the 90-100mm range.

I'll post some CAD drawings as the design comes along.

What do you guys think?

R-dubb screwed with this post 02-28-2007 at 04:28 PM
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Old 02-28-2007, 03:58 PM   #2
SOLO LOBO
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R-dubb,

Depending on cost, I would like a set for my WP Extreme's which are already shortened to the same legnth as the BMW stockers. If you are planning on making triples for non-shortened forks, I might not be able to play

Let me know.... CrazyIvan has used two different vendors for triple to put WP Extreme's and 50mm Marzocchi's on his airheads and might be a source for measurements....

Thanks for asking!

SL
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Old 02-28-2007, 04:20 PM   #3
RocketJ
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wp clamps

43s use 57mm lower clamps.
48s are 60mm.
Both use the SAME top clamp, 55mm.
Oh, Yeah 50s are 50mm.
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Old 02-28-2007, 04:23 PM   #4
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Quote:
Originally Posted by SOLO LOBO
R-dubb,

If you are planning on making triples for non-shortened forks, I might not be able to play
SL
I don't think that will matter. It just means that you don't put a spacer on top. You don't have a problem with where to clamp, although a taller tree is still better.
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Old 02-28-2007, 04:26 PM   #5
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Quote:
Originally Posted by RocketJ
43s use 57mm lower clamps.
48s are 60mm.
Both use the SAME top clamp, 55mm.
Oh, Yeah 50s are 50mm.
ooooh, I just reread my post and spell check fucked with the numbers my apologies. the listed hole sizes make no freakin' sense. The wall thickness variation is still 5mm. thanks for setting that straight. Will edit.
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Old 02-28-2007, 04:50 PM   #6
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Quote:
Originally Posted by R-dubb
ooooh, I just reread my post and spell check fucked with the numbers my apologies. the listed hole sizes make no freakin' sense. The wall thickness variation is still 5mm. thanks for setting that straight. Will edit.
My point is that regardless of fork tube size, the same upper clamp will work for the 43 or 48mm forks.
The WP steering stem is about 25mm longer.
At first, it might look like the bearings are the same. They are not. The BMW is taller, OD is larger and ID is smaller.
If you put a KTM inner bearing in a BMW race it appears to fit because of the taper. Anyway, that means to fit correctly the stem needs to be turned 1mm.
Solo, those spacers can be removed in about 20mins, no problem. I added them to mine. 9.8 inches of travel being enough for me.
One nice thing about the 50s is that you can slide the clamps anywhere you want. On the others, the taper limits adjustment.
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Old 03-01-2007, 08:43 PM   #7
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Rocket,

That is really good info. What I'm thinking about is using the KTM stem and turn it down like you say. Then make a spacer that will fit either on the top or the bottom depending which way it is inserted. OR, in the case of the conventional forks, we'll just use the BMW stem.

This should be a fun project. Too many ideas, too little time...
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Old 03-01-2007, 09:08 PM   #8
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RDubb

First let me say I've been using WHITE POWER suspension long before they changed there name to WP. I've a Dukey and 95OSM wearing them now.

The thing is you don't see many on fleabay for sale. What about making some clamps that fit late model CR250 Showas?? They seem to be the most plentifull on ebay followed by late model YZ250/WR etc.

I'm no genuis, but what about different size inserts with some type of set screw??
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Old 03-01-2007, 11:10 PM   #9
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Quote:
Originally Posted by bykpimp
RDubb

First let me say I've been using WHITE POWER suspension long before they changed there name to WP. I've a Dukey and 95OSM wearing them now.

The thing is you don't see many on fleabay for sale. What about making some clamps that fit late model CR250 Showas?? They seem to be the most plentifull on ebay followed by late model YZ250/WR etc.

I'm no genuis, but what about different size inserts with some type of set screw??
43mm WP's are a dime a dozen. Go for $150 a pair mostly on KTMtalk. 48's are still current, a little harder to find and go fast at $250. $400 for a premo top dollar pair. Extremes are more rare at this point, but reasonably priced as well. The other part I like about the WP's are the axels, brakes and wheels are fairly universal in the KTM world. Never mind the fact there are three. It comes down to the fact that I have a bunch of that shit in my garage and can connect the dots pretty well.

Yes, inserts good. Don't even need a set screw because the fork will clamp it in place. It will need to be slotted to allow movement.
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Old 03-02-2007, 12:50 PM   #10
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This little canadrum got me thinking about a good solution for this problem...

well I find a exelent way to cover all the bases and even provide a range of adjustments (up and down and fore and aft) with no extra parts.

oviuslly I can not show it to you do to the "other" shady business practices, but if is suffient market I will work on the R&D and then get a patent for it (yes is that radical, but also super dupper KISS simple)

the only problem is that i will need a much bigger volume than 10 units a years to justified the expense..

does anybody have any odea how big is the aftermarket market (pun intented) for this kind of conversion fork clamps..!?!?!?

I don't care if is in europe or new zeland, since if you build a good product they will come..
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Old 03-02-2007, 01:46 PM   #11
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Good of you to see who else want in R-dubb. I don't need a set but I had a question of course

Does the design assume an equal 'trail' figure for all the bikes?

- Jim

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Old 03-02-2007, 02:06 PM   #12
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Quote:
Originally Posted by Poolside
Good of you to see who else want in R-dubb. I don't need a set but I had a question of course

Does the design assume an equal 'trail' figure for all the bikes?

- Jim
Well since "all" the bikes are airheads, they all have 28 degree steering heads. They all presumably will have 21" wheels. So the only variable will be the leading axle offset on the fork being grafted. I think all the WP forks I've mentioned are the same offset. therefore the resulting computed trail will be the same for each application. There may be some variation for forks of different lengths, but that is not relevant unless the front to rear balance has been messed with due altered ride height geometry ie. to short a swing arm for the fork.
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Old 03-02-2007, 02:26 PM   #13
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Quote:
Originally Posted by R-dubb
Well since "all" the bikes are airheads, they all have 28 degree steering heads. They all presumably will have 21" wheels. So the only variable will be the leading axle offset on the fork being grafted. I think all the WP forks I've mentioned are the same offset. therefore the resulting computed trail will be the same for each application. There may be some variation for forks of different lengths, but that is not relevant unless the front to rear balance has been messed with due altered ride height geometry ie. to short a swing arm for the fork.
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Old 03-02-2007, 02:40 PM   #14
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R-dubb,


Any thought as to when these clamps might be built? even a rough guess would help !
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your bike is suitably dirty. Well done.
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Old 03-02-2007, 03:51 PM   #15
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Quote:
Originally Posted by SOLO LOBO
R-dubb,


Any thought as to when these clamps might be built? even a rough guess would help !
That is a tough question. Ricky would like to have his pair next week. I don't feel a strong need to have mine for perhaps 3 months. I've got a bunch of irons in the fire right now. The design could take another a month, a few weeks to bid out the machine work and a month or so to produce. Help you?
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