Project: Cool Kat II

[posplayr]

Well I FINALLY received the title for the Kat in the mail yesterday so this project can get going again. Better late than never I guess.

Congrats Russ, U have had more than your share of real head bangers that have worked out well.

[russr33]

Ok so a little progress. My buddy Jay fabricated what I think is a very cool fork brace. Whatcha think?





This is a prototype. He has a cnc machine and is going to make a few more with a slightly different design.

[Flaming Chainsaws]

That is quite different but pretty cool . I wish I had a CNC machine.

Looking good!

[Walle]

To me it doesn't look like that will stiffen things up at all. The "hinge" in the corner defeats the purpose. A tall brace, for the upside down fork, should either be wide or made of 2 parallel braces.

[Tim Tom]

I'm no expert on these sort of things but that fork brace seems like it would sway due to all the bolted connections. Also that is adding more unsprung weight to your front wheel. While it may work to some degree it seems flimsy to me.

If you have access to a CNC machine why not cut out a more traditional looking fork brace that clamps around the forks from the left and right side. I feel this would not only brace them better but also save on weight.

Again I am no expert and simply did a quick 5 minute CAD drawing based on how I've seen other fork braces.

Perhaps someone who is actually an engineer could verify my design concept (or tell me I should stick to architecture ) Whichever would be cool.

[tkent02]

To me it doesn't look like that will stiffen things up at all. The "hinge" in the corner defeats the purpose. A tall brace, for the upside down fork, should either be wide or made of 2 parallel braces.

+1, that ads very little stiffness if any. The two sides of the forks are still free to move independently by only bending that tiny end where the bolts go to the caliper mount. It does look like it could cause the caliper mounting boss to break off under certain circumstances. Longer legs catching two mounts on each side would be much better... Front forks are one of the worst places to play around with amateur engineering IMHO. Methinks the designer does not understand the forces involved.

Doesn't that fender have a real brace built in underneath it?
What do modern high performance bikes with upside down forks use for bracing?
Do they really need anything?

[salty_monk]

I'm very surprised that the upside down setup would need any extra bracing...

I'm also worried about your mounts. They are cast so probably quite brittle & will not like being "bent" across their cross section. If they fail they will just snap & you'll end up with a caliper & remains of a mount in the front wheel, most likely under situation of most stress which is probably when you're hammering it around a fast corner.

Dan

[tkent02]

I'm very surprised that the upside down setup would need any extra bracing...

I'm also worried about your mounts. They are cast so probably quite brittle & will not like being "bent" across their cross section. If they fail they will just snap & you'll end up with a caliper & remains of a mount in the front wheel, most likely under situation of most stress which is probably when you're hammering it around a fast corner.

Dan

Or when braking hard and hit a big hole or something.

[MadDogGS]

Upside-down forks don't need braces. That is the entire reason behind upside-down forks, is their strength.

[russr33]

First off the forkbrace was a prototype and really just for mock-up; Jay already wanted to take the side plates from 1/4" to 1/2" and do some other changes as well. This '05 GSXR1000 fender that came with the project didn't have the metal inner brace. Jay had seen a fork brace like this one a race bike. Will try to find a pic. He isn't exactly an amateur. He's been a mechanic and engine builder for 25+years.

I'll find out all the answers to the questions you guys have when I'm at the shop tomorrow.

I would think however that if the 6mm bolts holding my Tarozzi and Telfix forkbraces on my GS1000's with their flimsy front ends don't ever snap that the 10mm bolts that the caliper and brace share should be fine? Wouldn't you almost need the axle to bend to create enough force to snap that bolt?

David at FastBikeIndustries (#1 service provider for Ohlins) is doing the rebuild on some Ohlins shocks I have for the project. He also rebuilt the rear shock on my GSXR1100. I'll shoot him some pics and get his input. If anyone should know it will be him.

[tkent02]

He's been a mechanic and engine builder for 25+years.

Mechanic, engine builder and mechanical engineer are very different things.
That brace is dangerous.

[MadDogGS]

I would think however that if the 6mm bolts holding my Tarozzi and Telfix forkbraces on my GS1000's with their flimsy front ends don't ever snap that the 10mm bolts that the caliper and brace share should be fine? Wouldn't you almost need the axle to bend to create enough force to snap that bolt?

You won't have to worry about the brace flexing, breaking, bending, or breaking bolts. The upside-down forks won't flex. That brace is nothing more that a big chunk of useless metal that might run into your frame or fairing when your suspension travels through it's range.

[russr33]

You won't have to worry about the brace flexing, breaking, bending, or breaking bolts. The upside-down forks won't flex. That brace is nothing more that a big chunk of useless metal that might run into your frame or fairing when your suspension travels through it's range.

Then why do the gsxr1000 fenders come with metal inner braces? I know when you run without them there is a danger of warping rotors right?

[MadDogGS]

Then why do the gsxr1000 fenders come with metal inner braces?

To strengthen the fender?

I know when you run without them there is a danger of warping rotors right?

I haven't heard that one.

But upside-down forks have no advantages what-so-ever, except for their strength and their tendency not to flex.

[tkent02]

And a large reduction in unsprung weight?