Strongest seat post rack
- Thread starter Doctorbass
- Start date
dogman dan
1 PW
Those frames kick ass! I like the idea of going retro, and using two shocks in the rear just like the old school motorcycle suspension. Or if monoshocked, there are lots of ways to build a rack into the frame. The seatpost attach idea is lame. Just a few welded on brackets in the right spot would allow a bolted on rack that's far stronger like the example on the tandem.
I'd get cracking if I could weld at all.
I'd get cracking if I could weld at all.
docnjoj
1 GW
I'm waiting for this rack so I can carry stuff again. Stein claims 50 kilos and it is bolted to the frame, not the suspension, but I still don't want to put 20 lbs of batteries up that high. It gets tippy, I believe with a trike. Definitely want the weight as low as possible. Rack will be for groceries etc. and some panniers.
otherDoc
Patriot
10 kW
- Joined
- Aug 7, 2008
- Messages
- 511
Doc,
Since you have a Mongoose, similar to mine, you could do what I did. I made an addition to my existing 25lbs capacity Transit rack. It works really well. Since your rack has the same double seat tube support setup as mine, it may work. I made it out of simple 3/4" angle iron. What's really nice is the double tube support prevents it from any possible swaying when riding.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=10885
Since you have a Mongoose, similar to mine, you could do what I did. I made an addition to my existing 25lbs capacity Transit rack. It works really well. Since your rack has the same double seat tube support setup as mine, it may work. I made it out of simple 3/4" angle iron. What's really nice is the double tube support prevents it from any possible swaying when riding.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=10885
Doctorbass
100 GW
Patriot said:Doc,
Since you have a Mongoose, similar to mine, you could do what I did. I made an addition to my existing 25lbs capacity Transit rack. It works really well. Since your rack has the same double seat tube support setup as mine, it may work. I made it out of simple 3/4" angle iron. What's really nice is the double tube support prevents it from any possible swaying when riding.
http://endless-sphere.com/forums/viewtopic.php?f=6&t=10885
That is a great idea and nice job for this model Patriot
But the bike i need to put the rack on are different!.. I have 7 bike to modify.. so i need a less complicated way!.. did you saw page 3 of this thread?.. I shown a pics of the similar bike i'll need to put the rack on.
Doc
:wink:
Patriot
10 kW
- Joined
- Aug 7, 2008
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- 511
Doctorbass said:
OOOOOOHHHHHH....
Stupid me.
In that case, since it appears very difficult to build anything easy for that particular frame, then I would suggest using the AXIOM ODYSSEE seatpost rack, which was posted earlier. It does have a 25kg rating, and is the beefiest I found when searching for a strong seatpost rack when building my bike a couple months ago. They use brass bushings and heavy duty bolts for the extra strength. I've seen one before, and they are very stout compared to most others.
Also, if you are loading up that rack, I suggest you try and find a STEEL seatpost to replace the cheap aluminum post that comes with the Cadillac bike.
ElectricEd
100 W
I've posted this piccie before but (brain fade) have forgotten where. I have been using this setup for about 6 months now. The version in the picture had the aluminium tubes bent too much so they eventually fatigued and cracked at the bend. I now have them straightened out much more and the fatigue has stopped. The tubes were from an old TV antenna made back in the middle 60s, so I have doubts as to the quality of the alloy. If they fatigue again I'll get some thicker walled tubing from Alcoa. That should beef it up a bit. The copper tubing aroud the bolt points are to reinforce the aluminium at the high stress points.
This is the cheapest way that I can think of to strengthen a seatpost rack and keep the weight down at the same time.
This is the cheapest way that I can think of to strengthen a seatpost rack and keep the weight down at the same time.
TylerDurden
100 GW
ElectricEd
100 W
BVH said:
Hi BVH,
it's a galvanised plumbing pipe clamp. They are made up from two pieces (exactly the same) that interlock around the seat tube. They are used for clamping water pipe to a "T" that is mounted on a bracket or wall. They come in all sizes to suit either copper or gal water pipe, so you'll have no problem finding one to fit your seat tube. Any plumbing supplier carries them.
I'm sorry that I cant post a picture of it, my camera is out of action at the moment.
dogman dan
1 PW
The axxiom rack is pretty nice. It's the one I'm using, with the metal braces. It looked pretty unbreakable to me, but I put on the bacing to help the steat tube stand it more than anything. I pound broomsticks up seat tubes to strengthen them now too. My bent one was bent a lot more before I put a stick inside.
No matter what the bike is like, there should be enough space to put in some kind of short brace between the rack and the point where the seat tube enters the frame, even allowing a little bit of seat height adjustment. All the rack really needs is to have the point where the tube clamp welds to the beam supported since that or the clamp itself seems to be the point of failure. I put my braces on further along simply because it made a great way to attach a fender that way.
A very inexpensive post rack could be cut short, and then a small brace could be put on between the cut rack and the actual rack to add support. At wallmart I was able to buy a steel and plastic rack for about $12 that would be perfect for this, allowing a brace to be added without drilling a hole in the seatpost. I made my bracing out of steel tube simply because I had it in the yard. Aluminum square tube would work great and still be light, and stronger than tv antenna stuff.
No matter what the bike is like, there should be enough space to put in some kind of short brace between the rack and the point where the seat tube enters the frame, even allowing a little bit of seat height adjustment. All the rack really needs is to have the point where the tube clamp welds to the beam supported since that or the clamp itself seems to be the point of failure. I put my braces on further along simply because it made a great way to attach a fender that way.
A very inexpensive post rack could be cut short, and then a small brace could be put on between the cut rack and the actual rack to add support. At wallmart I was able to buy a steel and plastic rack for about $12 that would be perfect for this, allowing a brace to be added without drilling a hole in the seatpost. I made my bracing out of steel tube simply because I had it in the yard. Aluminum square tube would work great and still be light, and stronger than tv antenna stuff.
After breaking a seatpost rack after few hundred miles, I since mounted my battery/controller on the seat post itself.
I fabricated an aluminum plate attached from the inside of the leather battery bag and bolted it using seatpost water bottle clamps.
Since I use a small battery pack (Bosch fatpacks 6AH 36V), mounting the battery this way also gave my bike better handling since the weight of the battery is inline with my weight when seated on the bike. It is a very strong setup; I now have over 2500 miles with this configuration without any problems.
I fabricated an aluminum plate attached from the inside of the leather battery bag and bolted it using seatpost water bottle clamps.
Since I use a small battery pack (Bosch fatpacks 6AH 36V), mounting the battery this way also gave my bike better handling since the weight of the battery is inline with my weight when seated on the bike. It is a very strong setup; I now have over 2500 miles with this configuration without any problems.
ElectricEd
100 W
spinningmagnets said:
I've knocked up a quick drawing of the clamp...
GreenKnight
10 mW
I like spinningmagnets design but I would put the downtubes back on the axles and place a hinge joint near the seatpost.
otherwise
split the load and get some of it up front of the handle bars. This would also improve handling.
otherwise
split the load and get some of it up front of the handle bars. This would also improve handling.
Hi guys, I now have this same Topeak rack problem, where it sways as I go on a journey!
My idea is to create a better bond between the clamp and the seatpost, either by gripping both surfaces with a keying of somekind, or by using something like threadlock or superglue to create a permanent bond.
Anyone have any thoughts on this, or a recommended bonding agent for rubber-alloy? epoxy resin any good (i have some at home!)
Ger
My idea is to create a better bond between the clamp and the seatpost, either by gripping both surfaces with a keying of somekind, or by using something like threadlock or superglue to create a permanent bond.
Anyone have any thoughts on this, or a recommended bonding agent for rubber-alloy? epoxy resin any good (i have some at home!)
Ger
DarthSensate
1 W
- Joined
- Sep 5, 2008
- Messages
- 53
I was just reading this entire thread to see if that had been suggested yet. I have the Axiom Odyssee rack rated at 55lbs cap. and want to make sure it does not rotate on the seat post as others have mentioned.gerlewis said:
My plan was to use a drill press and bore a hemisphere into the seat post and a matching hemisphere in the clamp plate of the seat post rack and place a matching diameter ball bearing in the two hemispheres. I don't know if the bearing would be a better idea that a key slot cut with a grinder or not. Seems to me the shearing strength of a small ball bearing would be greater than a key and would require a smaller cut into the post and clamp surfaces without cutting through the metal.
I wasn't going to use the rubber grip stuff that came with the rack at all. metal on metal and galvanic compatibility be damned.
I like the broom stick in the seatpost idea as well.
It occurs to me that many of the Wally World racks are not ovalized tubes and would benefit from a broomstick shoved up them as well. The weak point would then be the weld at the seat post clamp. Welding a cuff around that would do well I think, just as with double butted frame joints.
good idea with the ball bearing, what you thinking, 4mm - 5mm?
A grub screw glued in place might do a similar job, though im not sure where on my clamp I could drill a hole to be honest.
I need to do something, as its not up to the job as it stands, swaying this way and that.
Ger
A grub screw glued in place might do a similar job, though im not sure where on my clamp I could drill a hole to be honest.
I need to do something, as its not up to the job as it stands, swaying this way and that.
Ger
rguy56
100 W
There are implications to the seat post itself if the weight gets excessive.
I think it may work well to find two racks that nest well on each other and clamp them one over the other on the seatpost. If you were to do that and add struts between the two, I think the major limitation would be seatpost strength.
I think it may work well to find two racks that nest well on each other and clamp them one over the other on the seatpost. If you were to do that and add struts between the two, I think the major limitation would be seatpost strength.
DarthSensate
1 W
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- Sep 5, 2008
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gerlewis said:
As small as I have on hand. I don't think it will take much at all to stabilize the clamp laterally on the seat post. As long as the clamp is tightened down really well, its not going to jump the bearing unless you drop the bike. My primary concern is to do as little to impact the strength of the seat post as possible.
I could definitely see a set screw in a threaded hole in the clamp as a workable solution. ... not sure how many threads you could get in the thickness of the clamp's plate.
DarthSensate
1 W
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- Sep 5, 2008
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rguy56 said:
I think the broom/rake/shovel shaft fiction fitted in side the seat post idea would do a great deal to strengthen the post. Got to be good hardwood shaft though and not the crappy yard rake replacements you find at Wally World seasonal. I about tore my arm open on one of those stupid pine shafts when it snapped in half the first day I put it on a rake.
ion
1 µW
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- Sep 24, 2011
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I have about 23 pounds on my rack and it was breaking at the first weld off the seat post. I took a steel angle iron measuring 1.25” X 3.25” long and centered it on top over the weld on the new rack. Then I took 4 hose clamps and placed two on one side of the weld and two on the other side of the weld to hold the angle iron to the rack. The rack had a slight angle at the weld but the hose clamps still held the angle iron tight. I used a socket wrench to tighten the clamps and about 10,000 miles of bumps later they still are holding tight with no more cracks in the welds. You could use two angle irons on opposite side but one worked for me. Just make sure the steel angle iron is 1.25” wide and no wider or it might extend over the edges of the rack tube giving it a weaker fit.
I'm looking for a good seat post rack too. I've got it narrowed down to either the axiom odyssee (the seat post only version) or the delta post porter rack. I'm leaning towards the post porter based on more positive reviews. Are these the two strongest seat post racks available right now?
I don't want to spend too much $$$. Anyone know where I could pick up a good seat post rack from within Canada to avoid brokerage fees ? Any other suggestions?
I bought a cheap used full suspension mountain bike to use as my new commuter but I didn't realize I'd have to spend so much on a rear rack and worry about it snapping off while I'm riding.
I don't want to spend too much $$$. Anyone know where I could pick up a good seat post rack from within Canada to avoid brokerage fees ? Any other suggestions?
I bought a cheap used full suspension mountain bike to use as my new commuter but I didn't realize I'd have to spend so much on a rear rack and worry about it snapping off while I'm riding.
