Building a swing arm (help needed)

[gensem]

I plan on making a swing arm to replace my broken one, but im not sure what steel alloy should I use.

http://img688.imageshack.us/img688/681/bicicletinha.jpg

I ll make the arm 2" longer and wide enough for 4" tires. I can order any off thoses alloys for the tubes (im gessing 4130 should be my choice)

SAE 4140
SAE 1045
SAE 4130
SAE 8620
SAE 8630
VMec 134 AP
ST-52.3

Dropouts be ll around 15mm, but im not sure about the tubes wall diameter.

Thanks

 

[Drunkskunk]

I'm in the process of doing exactly this for 4" wide tires as well.

What I've found is that standard mild steel would be strong enough. (1010 or 1018) and has some nice flex properties that would be good for a swing arm. (not much flex, but it will bend further before breaking than some other alloys)

But I'm going for 4130. Its stiffer and stronger. Which means I can get away with a less-than-perfect build and still have a strong enough swing arm.

 

[gensem]

I'm in the process of doing exactly this for 4" wide tires as well.

What I've found is that standard mild steel would be strong enough. (1010 or 1018) and has some nice flex properties that would be good for a swing arm. (not much flex, but it will bend further before breaking than some other alloys)

But I'm going for 4130. Its stiffer and stronger. Which means I can get away with a less-than-perfect build and still have a strong enough swing arm.

How tick are the tube walls your going to use?

 

[Thud]

.049" is considered heavy wall for bicycle stuff.

you can go .035"t if your welding skills are up to it.

 

[Drunkskunk]

I'm using .065" for the swingarm. Overkill, but but I'm building for a 10kwatt+ motor and some planned abuse. And it will be easier to weld. I stake my life on my welds, and have been doing it for years, but I'm very much an amature.