Got tired of the pansy rear racks...

[BrandonB]

After 200 or so miles of riding, my rear rack finally gave in a few days ago. I totally bent the rails connecting the rack to the seat post, so I ordered some more...went to put them on, and the rails that hold the rack to the bottom of the frame were bent about 45 degrees out of place and ready to snap aswell, the rack was resting on the rear brake caliper :lol: As cheap as I am and as much as I don't want to keep replacing parts, I decided to build my own and be done with it. I started with some 3/4" square steel tubing, and after I got it welded, came out with this:

I plan to come upwards with the same steel from the frame to the bottom of the rack, and to connect it to where it barely clears the rear wheel for a better center of gravity. I may also brace the very end of the rack to the rails going to the bottom of the frame to give it a motocross style look. I decided not to brace the rack with the small piece pictured towards where it mounts to the seat post in order for it to be able to be snugged down to the seat post and not have any play. Whaddya think?

 

[morph999]

nice...did you ever look at the axiom racks? They look strong. I wonder why the bike racks that are available suck so bad. I have a topeak and it's pretty good but it does sway about 1/4" if you really shake it hard enough. That annoys me a little bit. Why can't we have 3 ways to attach it on each side instead of two. Right now there is one at the seat post and one near the rear axle. It'd be nice to have one more that attaches to the arm down below.

 

[BrandonB]

After looking at the Axiom racks, they are made pretty much the same way my old one was. That 1/2" thick or so round alloy gives way too much for the battery I use (Six 12V 7.2Ah wired for 36V 14.4Ah) and eventually did begin to fail under the stress. Most of the bike racks made now aren't made to hold such a payload, and the ones that are are ignorantly expensive because of the niche market they cater to. Even the ones specifically made for electric bikes are usually made out of the same material that regular ones are. My rack will be alot sturdier, and I will be making a cavity for the battery out of angle steel of the same thickness for the battery to fit in. One of the other main problems I had was the battery swaying from side to side on the rack in turns due to the straps not being able to hold it firmly enough in place; I think that was one of the contributing factors to the beginnings of failure for the rack aswell.

 

[morph999]

you have one of those nice schwinn bike seats. How do you like it? Can you still pedal with that seat? I was thinking of one day getting that.

 

[BrandonB]

I like it alot. I can still pedal with it, and it doesn't affect the way I pedal at all; someone with a more efficient pedaling stance may be affected, though. It's extremely comfortable, and when you aren't pedaling and on electric power only, it's comparable to the ride of a moped. It's definately better than a standard biking seat, in my opinion. The thick gel seat absorbs some of the shock during bumps aswell.

 

[amberwolf]

With the SLA on there, the one thing I would do is add the stuff I drew in green. For the X brace it can be thin round tubing if you like--as long as it is welded in place it will help fix the back end from swaying sideways, which will help with fatigue from bending at the mounting ends.

I think that sidesway fatigue is what breaks a lot of racks, rather than anything about how thick or thin the tubing is.

 

[dogman dan]

Looks nice, you can hardly have a rack too strong for sla's. But if you carry 4, you should carry them pannier style, with two on each side even lower.

 

[Solcar]

With the SLA on there, the one thing I would do is add the stuff I drew in green. For the X brace it can be thin round tubing if you like--as long as it is welded in place it will help fix the back end from swaying sideways, which will help with fatigue from bending at the mounting ends.

I think that sidesway fatigue is what breaks a lot of racks, rather than anything about how thick or thin the tubing is.

I run some vertical supports up from slightly before the rear axle so as to get use of two frame members for lateral bracing. I build my racks out of honeysuckle bush sticks, rebar tie wire, and nylon zip ties. They can be made pretty strong.

 

[chrisvw]

I'd suggest you modify your "green" supports to be vertical rather than angled to the back. My old statics class tells me that the weight of the batteries would rest vertically onto these supports. Keeping it vertical will stress the vertical supports less (cosine of angle). Having a bit of a cantilever on your horizontal rack shouldn't hurt anything. At worst, build a little triangle from the vertical support to the back to support the back edge of the rack.

 

[amberwolf]

The only reason I would use the rear-angled side supports is for longer X bracket length, for anti-sidesway.

 

[02jze]

Having that weight on the rear rack makes for a shitty ride imo. i had my 4x12v sla's like this

Then i put the second one in a bag and and put it in the triangle. The bike feels so much lighter..

 

[dozentrio]

Axiom +1

I have an axiom rear rack, for full suspension bike (it clamps only to seatpost) and I've had three 12v 12Ah SLAs on it. It is briefly visible at around 5 seconds into this video

http://www.youtube.com/watch?v=sd9HhXB7oaA

My drivetrain was badly aligned, disregard the horrid clicking noises coming from the chain

 

[recumbent]

... you can hardly have a rack too strong for sla's. But if you carry 4, you should carry them pannier style, with two on each side even lower.

Dogman" is right, best way to carry batteries, they're hidden, low CG and you have room with another trunk pack on top for groceries and stuff.