custom swingarm

[400sEXridr]

hey has anyone made a custom swingarm for a 400ex?

[gcart2]

i have not but i race mx and after nearly after race i have to take mine off and have to weld up a new crack. I am pretty good at working with metal (especially for being 15) and have a few good friends that are master mechanics and i think we are gonna giv it a go once i break mine in half lol.

[TRXRacer1]

I haven't made one for a 400ex but I have made a few for other machines. What kind of info are you looking for?

[400sEXridr]

well im planning on making one for my quad just looking for any tips (what you would have done different) what material thickness, how difficult it was, any insight really

[TRXRacer1]

A swingarm build is difficult in the sense of designing it to be safe. This single part probably takes more abuse then any other on the rest of the machine. I was building a quad tube style swinger too that I would probably not do again. They look cool but just take too much time.

First great tip is just buy the pivots and housing and make the rest. For machines like the 400ex these are easy to get. I bought all of mine from jjandaracing and always got quality parts. Add a .com and you have it.

Second tip is go chromoly and never look back. For the DIY project like this Aluminum tends to break at the connection near the pivot bearings. Chromoly is actually pretty easy to find at aircraft part suppliers and it's very strong. I bought all of mine locally from Wag Areo. They also have a web site.

Third tip is build a jig even if it's out of wood and measure, measure and measure again. A swingarm has to be strait and square. Consider how everything lines up.

Fourth, even though I weld almost everything I need for myself I hired this welding out. Maybe you or someone you know does good TIG welding, I'm just a stick and MIG kind of guy. Make sure all of your joints are clean and tight.

As far as thickness and tube size goes, every design is a little different. This kind of gets into an area I'd rather stay out of. I will say this though, it is surprising how thin the tubing walls can be.

Here's a couple pics of 250r swingers I made before paint. The top one is the underside of and 82 ATC, the arched brace is to clear the odd shock set up they have. The other is an 86 TRX/ATC swinger. Like I said though, I wouldn't bother with the quad tube style swingers, just make a standard twin tube.

http://miltechsolutions.tripod.com/offroad/mtr/gifs/underside.jpg
http://miltechsolutions.tripod.com/offroad/mtr/gifs/swing.jpg

[400sEXridr]

i was planning on using rectangular tubing turned on end in place of the quad tube design with a round tube for a linkage mount. is chromoly really that much better than mild steel for the price? i plan on tigging everything myself and am very confident in my welds. is there one specific housing for the 400ex or one you would recommend on the jjandaracing website? what wall thickness did you use on the tubing?

[TRXRacer1]

Chromoly really isn't that expensive when you consider how little you're going to have to buy. I was able to buy it by the foot. Another place to look for small quantities besides aircraft parts dealers is race car shops. I have yet to find an actual steel dealer that doesn't completely bend you over for these little projects. Mild steel works fine too but it will be heavier in order to achieve the same strength as a chromoly piece. My first swinger was made with DOM (mild steel) and it was quite a bit heavier.

If you don't see a 400ex specific housing give them a call. They were really good people to deal with.

What wall thickness........... that's like asking for the secrete recipe lol.

[400sEXridr]

hey thanks a lot for your help. do you think rectangular tubing would be the way to go or would i be better off with round?

[TRXRacer1]

Originally posted by 400sEXridr
hey thanks a lot for your help. do you think rectangular tubing would be the way to go or would i be better off with round? Rectangular would be a real good way to go. You'll get a ton of bite on the housing and you can fab the other end to get a lot of contact on the pivot tubes. The pivot tube connections are the weak link so get as much contact as you can. Also the rectangular face makes for easy work installing inserts and what not.

Good Luck!

[Ruby Soho]

my dad and i are going to fab one up, were going to make it similar to the roll design swingarm, very close with stock dimensions. its going to be some sort of steel, and were going to make it as strong as possible.

[400sEXridr]

what differences are there between aftermarket and stock swingarms that make them worth so much money

[Ruby Soho]

basically because they're chromoly. but there not worth 600-1000 for it, they are such simple designs, thats why im going to make one, i have access to a steel shop, im good with fabrication, and my dad is a genious at it, so were going to give it a couple tries and see how they come out

[400sEXridr]

can someone give me basic dimensions like housing length, pivot sleeve outside to outside distance and overall length? im at college right now so i cant go out to my garage to measure unfortunately, but i would like to draw a basic sketch of it in Pro E and do some stress testing in order to try to find the most efficient way of gusseting everything that needs it

[400sEXridr]

anyone?