Tried Topeak Beam seatpost rack with panniers

[MikeSSS]

This was the type V rack, it angles down from the seatpost and then horizontally back. It carries the load lower than a straight backward rack.

Side frames are available to carry panniers. Topeak makes a really nice quick disconnect bag with panniers to fit on this rack.

Got this to carry my 52v, 20ah battery in one of the panniers.

The battery fit and carrying it low was better than carrying it on top of my existing straight back rack. Bike is a 1997 Mongoose FS that is difficult to position a battery on.

Problems were that the seatpost clamp had rubber bushings and did not have secure enough hold on the seatpost to prevent rotation side to side. Also, there is a cross piece on the back of the panniers that is too close to the tire during suspension travel.

The seatpost rack I've been using has a much better grip on the seatpost, but positions the bag higher and does not have provision for panniers.

Well, like they say at Boeing, back to the drawing board.

PS, I've made a rack to carry the battery on top of the bikes top tube, it works but looks bad.

 

[Balmorhea]

Seatpost racks are for carrying a windbreaker, a lock, and a sack lunch. If you really load them up, you’re bound to break something.

 

[miro13car]

exactely
have you seen seatpost rack loaded with battery pack ?
every such seatpost rack supposed to be rated for weight , right?

 

[markz]

exactely
have you seen seatpost rack loaded with battery pack ?
every such seatpost rack supposed to be rated for weight , right?

Correct, rated for weight but not compensated for vibrational stress points or G-force load when popping over logs or curbs.

 

[JackFlorey]

Problems were that the seatpost clamp had rubber bushings and did not have secure enough hold on the seatpost to prevent rotation side to side.

That's the problem with every seatpost rack I have tried. You need a positive detent to keep it from rotating.

 

[markz]

I just add some extra bracing but thats easy for rigid frames. The benefit for seatpost mount rack is for full suspension.

 

[MikeSSS]

The bike is full suspension, I should have mentioned that.

For 250 miles a seatpost rack has been used to carry the 12.2lb battery, that rack has four bolts, with no rubber bushing, holding it to the 31.6mm seatpost, it has never had unwanted rotation. This seatpost rack has carried the battery on top of the rack, so the center of gravity, with no rider, is high and aft, that's a problem when stopped, not so much when riding.

Riding is slow, in the 12 to 17 mph range, my average is usually in the 12's.

Moving the battery to the top of the top tube doesn't change things much when riding but is an improvement when stopped. It does call attention to the bike though.

So I tried moving the battery to a pannier on the rear rack, that helped things when stopped, handling when riding about the same as the other two battery mounting positions.

Next I'll mount the battery against the left side of the top tube and down tube, that will give a lower CG and move the CG forward compared to the two rear rack mounting locations.

If that doesn't work I'll try a late 90's GT LTS, the battery might fit in the front triangle, this would be the best solution.

 

[MadRhino]

I have made a custom rack of that kind. It was not for batteries, but for a passenger saddle. The mount was clamping the seat post, and the top tube 6 inches ahead of the seat tube. The GF was 95 lbs and the rack resisted for a summer without any damage, but at fall one day that I was riding the MTB trails alone, the rack did hit in a crash and scrapped the frame.