Strongest seat post rack

Doctorbass

Doctorbass

100 GW
Joined
Apr 8, 2007
Messages
7,496
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Quebec, Canada East
There is still something that i need to solve about full suspension bike rack.
Most of them are rated 10 kg and some are 15kg (I mean the seat post model)

Butthey are generally made of aluminium. and when we put let say a 48V 15Ah lifepo4 battery on it that weight around 17lbs + the charger 4 lbs + the bag 2 lbs that weight become more like 23lbs load

I still think this is borderline eventhough it is rated 30lbs.
The movement of the bike with every shock due to many crack or put holes on the road often create violent movemebnt on the seatpost and the battery mass may add stress because it just can't follow that fast movement of the bike frame via the seatpost.

I broked 3 rack tube rack from now and i NEVER overloaded them
(never carried more than the max recommended load).

R.I.P. seatpost rack:

-Topeak 25 lbs rated price 49$ …..load was 22lbs
-Voyager 25lbs rated… load was 15lbs
-Canadian tire 20lbs rated.. load was 20lbs

Every time the rack broke at the same place: just after the clamp on the seatpost where the rack tube is soldered on.

Aluminum can’t be bended and I think that it’s the multiple shock that created the stress and weaked the rack tube.

Now.. I’m searching for a STRONG seatpost rack.. the best would be to get it made of steel !

Any idea or recommendation?

Thanks for any of your recommandations

Doc
 
I got one from my local bike shop that had rivets holding it to the seatpost, and it seemed fairly strong. I'm not exactly sure where it is but I'll dig it up for ya. The only thing is, I replaced the (hollow) rivets with actual bolts. It's held up to everything I've put it through (college text books, YIKES!).

Edit: hey, I found it. http://www.bikeparts.com/productinfo/Dimension-Seatpost-Rack-with-Quick-Release-Mount-Black-38924-81909.html

It works like a charm for me, just dig out those pins and replace them with real bolts.
 
battery weight is deff an issue, the static load my not be over weight, but as soon as you hit a bump, the load goes way up, the bigger the bump the higher the load, like maybe double. Ive all ready torn 2 sets of bags do to bumps and 40lbs of batteries, and my rack looks like a pretzel. The recent post using 2in wide Velcro straps was great, (for bag support), just stick them to each other (peel and sticky back)(walmart $7) and it makes a great strap.

I'd double up the tubing somehow, or configure a triangle support in some fashion.
 
nineball said:
battery weight is deff an issue, the static load my not be over weight, but as soon as you hit a bump, the load goes way up, the bigger the bump the higher the load, like maybe double. Ive all ready torn 2 sets of bags do to bumps and 40lbs of batteries, and my rack looks like a pretzel. The recent post using 2in wide Velcro straps was great, (for bag support), just stick them to each other (peel and sticky back)(walmart $7) and it makes a great strap.

I'd double up the tubing somehow, or configure a triangle support in some fashion.
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Yes that is exactly what i wanted to explain.. the weight of the battery appear higher for the rack when hitting bump or crack on the road!



I thought i discovered the best choice for ebike seat post rack: ( 15kg rated!!)

3f84_1.JPG


But i also found that Ypedal had problem with this rack too... :(

(now zero kg rated... )

Chaos-brokenrack.JPG




So there is still
 
Hi Doc;

I don't have any experience with this rack but, might something like this work?

http://www.axiomgear.com/products/gear/racks/rear-racks/odysee-rear-suspension/

Cheers Greg
 
That's less expensive than the OMM racks I was going to suggest.
It's also rated for more weight and available through Norco.
I've yet to see a seatpost rack I'd trust for carrying anything more than a bag lunch and rain-gear.
 
both my seat post racks broke as yours did, In the exact same spot. One was delta post haste rack.

that is why I recommend hard tail mountain bike for conversion, you need two attachment points. I realize this does not help you Doc.

I recently bought the old man mountain racks, and they bolt to brake Boss they seem Very strong. And I centermount my ping battery now and save the rear rack for my lunch and clothes only. And one seat post rack still broke from the weight of my bike light battery ( a 7 amp hr lead acid)

seat post rack SUCK. do they make steel ones?
 
Ur pic doesn't show enough, but you need a brace on the bottom, to make a triangle. Doesn't take much, just enough to spread the load
 
CITY LIMIT ALLOY BEAM RACK BLK ROM ELEVEN81 IS WHAT I USE. iT HAs A 40 POUND LIMIT AND I CAN VOUCH FOR EVERY POUND THEN SOME. IT HELD UP MY 30LB LIFEPO4 BATTERY AND 10+LBS OF BOOSTER PACK.

http://www.bikesomewhere.com/bikesomewhere.cfm/product/285/1933/25069
 

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I just picked up my new bike today and it came with the linked Axiom Odyssey rack with a reported capacity of 55 lbs.

http://www.bikeparts.com/search_results.asp?ID=BPC306022
 
Thanks guys.. every of your suggestions are nice! :wink:

Spinningmagnet, I love your desing... if only they could exist for sale ready to use! :| the mecanical desing facilitate movement and distribute force in teh right direction!

I found the Axiom 55lbs seatpost rack very nice!.. it is at 34$ here: https://www.ebikestop.com/axiom_odyssey_seatpost_rack_black-RK6606.php

Doc
 
If you have a pair of broken seat post rack clamps laying around, I could weld you up a rack you couldn't break.

I could also make the rack itself designed to be a cage or box that the battery nests into nice and snug.

Or, if you wanted to go cut out pieces just as you want for a custom steel rack, you could ship them to me, and i would weld them all up for you for free.

-Luke
 
Are you thinking about just putting the cargo and/or battery load on top of the rack or are you planning to hang them on the sides (possibly in panniers)? If you hang them from the sides you then have to worry about the rack's ability to resist lateral sidesway so that it doesn't get mis-aligned and the load doesn't end up hitting or rubbing against your rear wheel.

I used to have the Topeak Rear Beam Rack with the side panniers. It's rated only for 25 pounds but it held 35 pounds of batteries just fine. The problem was this was a quick release clamp system and no matter how tight I clamped it to the seatpost it would eventually swing sideways and mis-align itself. The rack and cargo would end up rubbing against my rear tire. I think if you're planning to carry that similar kind of load you need to stay away from the quick release clamps and get a rack that you can bolt on tightly.
Mongoose1.jpg
 
I put a couple of braces on my seatpost rack, after having one break where it clamps to the post. The braces make a triangle to the bottom of the seat tube so at least half the weight is not cantilevered. That setup has had no problems with a 16 pound ping, and two more nicads for a total of 32 pounds on the rack.58 tooth commuter.jpg

The electrical conduit supports also make a handy attach point for my closed cell foam rear fender. They just attach with a couple bolts through some holes I drilled. I picked out a presumably stronger rack, since it has pannier supports. When riding cross country, I have put about 4 water bottles on a bag on top of the battery box too, another 10 pounds?

All this makes the seat height not adjustable, but nobody but me rides this bike anyway. Got another one for the wife or freinds to ride. It seemed to help with the tail wagging effect too. There are a lot of side to side forces on the rack too.
 
dogman, can you do a close-up picture of that brace?

I think that's really the best kind of solution. On many bikes there may be an existing bolt hole for the suspension that could be used to anchor the brace, or you could use a second tube clamp.
 
Yup, hard to see in that pic, (Dogman) but the bottom triangle brace is what I'm talking about.
 
this idea works great and its heavy.
two 12v 20ah sla
36v sony pack
controller
wiring
fuses
and two pieces of plywood on the inside to protect cells.

as you can see in the pics i removed the cheap aluminum clamp that came with the rack and replaced it with a steel rod and goose neck. i even let a someone sit on the rack it will flex but not bend.

and it easy to build.

cheers
 
Very clever and interesting that you used a gooseneck (that's normally attached to the steerer tube of front forks) but instead have it attached to the seat tube. The gooseneck's clamp mounts are definitely strong and fasten securely to the seat tube. But how does the rest of the rear rack attach to the gooseneck? It's difficult to see from your 1st 3 pictures because they are zoomed in to close.
 
Yeah, I meant to get a better pic of it yesterday afternoon, but it was about 120 in the garage. I'll do it today, after a ride in the mts, and the TDF. It's a simple fix, at a cost of about 5 bucks. At first I wondered if the holes would crack the frame, or the rack, but so far no problems, and it's carried as much as 40 pounds on some rides of 60 mile length.

Ok, back from fun, and here's the pix. It's stupid simple, the way I do things. Just two pieces of steel tube, I had 1/2 inch electrical conduit laying around but anything would do. Angle stock, square tube, old ski poles, even horrors, wood. The angle is very steep, but as long as you form a triangle it's pretty good support, transfering a lot of weight to the bottom of the seat tube on the bike frame. Avoids the bent seat tube issue too.Post rack support 1.jpg

And from the other side, aslo showing a good veiw of the ghetto foam fender.Post rack support 2.jpg
 
NIce dogman!
It even gives a good mounting locaton for your makeshift mat/foam fenders. :D
Hey how well does the setup resist sidesway?
Does the rack ever shift left or right and end up rubbing on your rear wheel?
 
Also could be a place to mount a controller in that little triangle once the fender keeps that spot dry. Fill in the sides with sheet aluminum, and it would be tidy, secure , and dry. My style will allways be ghetto though. If I make it look enough like a homeless guys bike It won't get stole.
 
Hey dogman,
Like the rack. But looking at this pic, Is it just me, or does your seat tube look not quite straight. :?

dogman said:
The angle is very steep, but as long as you form a triangle it's pretty good support, transfering a lot of weight to the bottom of the seat tube on the bike frame. Avoids the bent seat tube issue too.
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