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Triple tree fabrication #774575
05/23/19 11:20 pm
05/23/19 11:20 pm
Joined: Nov 2015
Posts: 68
Schenectady NY
N
Notthepainter Offline OP
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Notthepainter  Offline OP
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Joined: Nov 2015
Posts: 68
Schenectady NY
Hi!

I talked to a guy at work who's retiring end of June. He's in charge of a water jet machine and he doesn't mind making a few parts for me. I've been thinking of adapting some cbr600 f3 forks on my 1978 t140. So I think I'll ask him to make some yokes and a disc adapters (I'll have a stem turned somewhere else). I have no experience making such things. That's a good opportunity to learn.

- is Al 6061 appropriate for the yokes? For the disc adapter?

- Anybody would know which tolerance I should use at the lower yoke / stem interface?

- Anybody think it's a bad idea?

Tank you!

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Re: Triple tree fabrication [Re: Notthepainter] #774620
05/24/19 6:49 pm
05/24/19 6:49 pm
Joined: Jan 2004
Posts: 4,041
ca, us
D
DMadigan Offline
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DMadigan  Offline
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Joined: Jan 2004
Posts: 4,041
ca, us
Water jet is not very high tolerance, especially when cutting thicker pieces. The jet tends to wander at the bottom of the cut and unless cut slowly the bottom cut trails the top. As a way of roughing them out it works but you have to machine the tube and bolt holes anyway so you do not save any time water jetting first.
You will not be able to hollow the underside by water jet so more machine work.
Why not use the CBR yokes and make a stem to fit your frame?
The disc adapters will have to be machined.
6061-T6 is a very common alloy. "Appropriate" depends upon your design and the loads.
Machinery Handbook gives interference for press fits.

Re: Triple tree fabrication [Re: DMadigan] #774723
05/26/19 12:07 am
05/26/19 12:07 am
Joined: Nov 2015
Posts: 68
Schenectady NY
N
Notthepainter Offline OP
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Notthepainter  Offline OP
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Joined: Nov 2015
Posts: 68
Schenectady NY
Hi DMadigan,

Thanks for your answer!

Yes other people have told me the same since I posted. Water jet won't be accurate enough, especially for the interference fit for the steering stem.

It's ok though if I cannot hollow the underside.

There are drawbacks to reusing the cbr600 yokes. They're ugly, the steering stops won't work as well, the Honda steering stem is much larger than the triumph one which means making an adapter... And it says "Honda" on it! But maybe I'll change my mind once I see an estimate from the machine shop.

I'll do some research and post some updates.

Re: Triple tree fabrication [Re: Notthepainter] #774938
05/28/19 11:59 am
05/28/19 11:59 am
Joined: Dec 2004
Posts: 9,845
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,845
Scotland
There must be a US version of this guy

https://www.topyokes.uk/

As well as the yokes listed he will do custom yokes ie CBR600 with a hole for a Triumph stem not a Honda stem.

Re: Triple tree fabrication [Re: kommando] #774964
05/28/19 4:02 pm
05/28/19 4:02 pm
Joined: Mar 2017
Posts: 69
aptos, ca, usa
T
t ingermanson Offline

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t ingermanson  Offline

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T

Joined: Mar 2017
Posts: 69
aptos, ca, usa
this looks like maybe the US version of the top yokes guy:

https://cognitomoto.com/products/custom-triple-tree-conversion-any-fork-to-any-bike

more expensive than your buddy at work, but results will be much better and safer too.

watch your ride height, rake, offset, and trail numbers. i don't want to sound like a know-it-all or worry-wart, but those numbers are vital to keeping the bike working well and keeping you safe. no joke. there are a lot of dangerous bikes out there with these conversions. the cbr fork will probably be much shorter than your triumph fork from '78. it will take some doing to keep the bike handling right.

Re: Triple tree fabrication [Re: Notthepainter] #774968
05/28/19 4:38 pm
05/28/19 4:38 pm
Joined: Dec 2004
Posts: 9,845
Scotland
kommando Offline
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kommando  Offline
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Joined: Dec 2004
Posts: 9,845
Scotland
Or just look up some yokes off a database.


https://litetek.co/Guide_USD_ForkDatabase.html

and check what geometry it comes up with, I upgraded a Norton front end and ended up with Gen1 R6 yokes holding F4i forks with 20mm increased trail. I bought some special bearings that took the R6 stem and a perfect fit.

Re: Triple tree fabrication [Re: Notthepainter] #775500
06/03/19 2:11 am
06/03/19 2:11 am
Joined: May 2013
Posts: 841
Overland Missouri
O
old mule Offline
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old mule  Offline
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Joined: May 2013
Posts: 841
Overland Missouri
I used Honda VF500F forks on my 78 Bonneville, I wanted somewhat less trail for quicker steering, Honda yokes wrked. And I wanted a slightly steeper fork rake, 18 inch wheel did that. Bonus was speedo drive from RD250 front wheel, reliable Japanese speedo. I used single disc.
That for and Ohlins shockers transformed the bike, embarassed a couple first year Ducati Monster owners soon as I got it on the street.

Of course I have reduced the Triumph's value greatly, but I don't care. No restorer would want a post 1970 Triumph anyway, we used to say.


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