FJR rear rack design

[60Minutes]

Hi all,

3/4 inch square aluminum tubing brazed together, mounted using three of the five bolts used to secure the passenger grab rail. Easy to remove/replace, plenty of room to remove rear seat. Very strong. Can fit a huge bag on it no problem. Several long trips on it already and no sign of weld failure- even when ridden on some pretty rough dirt/gravel roads.

Hated the original rack(let) and don't like trunks.....so.

I was just learning the aluminum brazing technique so not all my joins are pretty, but they are mighty strong. Weighs under 3 pounds.

 

[mferriter]

Nice work, but QUICKLY do a search here on rear subframe cracks.

Would it be possible to cantilever this out from the main frame and not touch the rear subframe?

 

[SLK50]

A suggestion: move the rear mounting point forward to the two screws

to eliminate rotational forces on the rear subframe and prevent cracking.

 

[60Minutes]

The big bag was full of my camping gear. Nothing very heavy, just bulky. I know about the weight issues and the rear subframe. I figured I could put as much as a passenger back there without much trouble. If I'm wrong, please advise.

Probably could mount to main frame, but not sure where or how. More complicated design, probably.

Next prototype will probably utilize all three rear bolts. No use having them just sit idle.

The tricky part was getting it to mount under the seat. Pretty complicated shape down there.

 

[escapefjrtist]

Fugly but effective! LOL

Former member here had a similar set-up to support a large Pelican case. Worked pretty well and minimized the weight and cantilever on the rear subframe.

--G

 

[wfooshee]

The forward struts are well forward of the rear bulkhead and are well supported by the subframe. The rear posts are behind the rear bulkhead and will subject the bulkhead to the twisting force that results in cracks. Actually more such force than something on the stock rack. Let me explain:

A better rear support would have been the two holes that carried the posts at the back of the grab handles. Those are EXACTLY at the rear bulkhead, not behind it, and thus would produce a much smaller torque moment on the bulkhead. By leaving those out, you've actually removed the tension bracing that the grab handles provided to the rear bulkhead and have produced a weaker structure than stock. The grab rails are part of the structure at the back. They are loaded in tension by weight on the rack, and help the rear bulkhead resist the twisting load of that weight.

Using those two points instead of the one further back will actually be better supported by the bike's subframe, and any weight hanging out behind the rear bulkhead would be carried entirely by your structure and supported by the bike with very little affect on the rear bulkhead. I don't think you need the fifth bolt (your third how you have it now) at all. The stock rack needs that support because it's plastic.

EDIT: OK, I drew up (sorta) what I mean: