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 Post subject: $10 Fork Brace
PostPosted: Sat Jan 21, 2017 4:43 am 
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A rough and ready fork brace designed to stop the left fork leg from twisting under hard braking.

5 minutes with a dremel to smooth and fit the exhaust clamps. (nearly fitted beforehand)
Used some 3mm ss for the centre piece.

Image

A few tacks.

Image

Before welding.

Image

Coated with plasti-dip and fitted.

Image

I used plasti-dip to help the clamp grip the fork without tightening it too much and risk crushing the fork leg.

Seemed to work well on the short test ride, I'll monitor it closely for a while, and see if it moves or rubs the fork leg.


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 Post subject: Re: $10 Fork Brace
PostPosted: Sat Jan 21, 2017 8:53 am 
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Unfortunately your brace isn't going to provide much resistance to twisting which is the key reason for a fork brace. :sorry: Maybe weld some webbing on it to stiffen it up? Next is, as you mentioned, the concern for the minimal clamping surface to take the load without damaging the fairly thin seal housing. On the inside you could line the clamp with metal to give it more surface area but the round profile of the U-bolt puts all the stress in a small surface area. :pardon:

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 Post subject: Re: $10 Fork Brace
PostPosted: Sat Jan 21, 2017 7:10 pm 
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Thanks for the feedback mxrob!

Do you mean a gusset to stop vertical deflection?
As it is, it does seem to stop the twisting motion.

I agree that it is less than ideal with the small bearing area of the u-bolt, this design was about all I can manage at home with limited equipment.

I'll probably buy some 20mm aluminium and have a machine shop bore the holes for me. (they owe me a favour)

:s_smile


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 Post subject: Re: $10 Fork Brace
PostPosted: Sat Jan 21, 2017 10:16 pm 
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If it works or not I applaud the effort. The ability to think outside the box is where great new ideas come from.

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 Post subject: Re: $10 Fork Brace
PostPosted: Sat Jan 21, 2017 11:05 pm 
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Wallacey wrote:
Thanks for the feedback mxrob!

Do you mean a gusset to stop vertical deflection?
As it is, it does seem to stop the twisting motion.


Correct.. just think about what is happening when your forks twist... Grab your bars and hold your front wheel between your legs and twist. The legs are not moving straight forward/backward but are twisting in two different directions... no doubt your brace helps somewhat but if it was gusseted to reduce the flat plate from twisting it would be a lot stiffer. It would not take a lot of height to make a marked improvement. :good:

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 Post subject: Re: $10 Fork Brace
PostPosted: Sun Jan 22, 2017 5:43 am 
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PerazziMx14 wrote:
If it works or not I applaud the effort. The ability to think outside the box is where great new ideas come from.


Thank You :biggrin:


mxrob wrote:
Wallacey wrote:
Thanks for the feedback mxrob!

Do you mean a gusset to stop vertical deflection?
As it is, it does seem to stop the twisting motion.


Correct.. just think about what is happening when your forks twist... Grab your bars and hold your front wheel between your legs and twist. The legs are not moving straight forward/backward but are twisting in two different directions... no doubt your brace helps somewhat but if it was gusseted to reduce the flat plate from twisting it would be a lot stiffer. It would not take a lot of height to make a marked improvement. :good:


Good point! I think I'll go ahead and make the aluminium one, bit worried that the clamps might damage the fork.
It was a fun little project anyway!

Cheers :2_thumbsup:


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 Post subject: Re: $10 Fork Brace
PostPosted: Sun Jan 22, 2017 7:36 am 
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Full marks for initiative and thinking!

It probably wont do much to stop twisting but if you box in the crossover it will. I don't think vertical is an issue as the axle would have to flex for that to happen.

If you used bigger U bolts you could make a shim to wrap around the fork leg which would spread the load.

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 Post subject: Re: $10 Fork Brace
PostPosted: Sun Jan 22, 2017 8:53 am 
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Wallacey wrote:
A rough and ready fork brace designed to stop the left fork leg from twisting under hard braking....

Seemed to work well on the short test ride, I'll monitor it closely for a while, and see if it moves or rubs the fork leg.


The proof of the pudding is in the tasting - good on ya!

If I may suggest a poor man's load indicator: obtain some Torque Seal* from an aircraft engineer friend then apply three thin lines laterally (it is a toothpaste-like applicator) atop brace's cross piece at front, mid, & aft portions. Allow to dry, then go for a ride on pavement and exercise front brake. Being a frangible lacquer, dried Torque Seal will crack when subjected to any significant loads, so visually inspect lines afterwards for evidence of brace deflection. Reinforce or redesign as you deem appropriate.

*http://itwprofessionalbrands.com/dymon-product.php?product=1142

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 Post subject: Re: $10 Fork Brace
PostPosted: Mon Jan 23, 2017 4:47 am 
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Thanks for the encouragement and suggestions :biggrin:
enim57 wrote:

If you used bigger U bolts you could make a shim to wrap around the fork leg which would spread the load.


Good idea, I'll look into that.

Maybe some 3/4 x 1/8 alu flat, nice and easy to form.

palnut: I like the look of torque seal, $20 a tube on ebay !

The thing is, the bike is pulling up in a straight line, even under pretty hard braking. (road tyres and 320mm front rotor)

This says to me that the brace is doing its job.

A short video demonstrating the lack of flex.


:s_cool


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 Post subject: Re: $10 Fork Brace
PostPosted: Tue Jan 24, 2017 9:26 pm 
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Yep the aluminium will be a good thing.

I made a "mutha" of a brace for a 1000GTR and didn't feel any difference under braking, but fast hard bumpy bends is where I felt the difference.

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