full suspension rear carrier racks

SniperGaulois

SniperGaulois

10 kW
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this is an idea similar to a seatpost carrier, that distributes the weight to the whole of the top tube... the idea is basically to fasten 1 straight pole to each side of the horizontal top tube, that go past the seatpost, and together extend into a seat rack platform... this should be even better weight distribution than a seatpost rack because the weight will be a little bit forwards in front of the rider...
anyone tried anything similar already?
 
My solution was to double up on the seatpost clamps ( use 2 x racks ) and then fill the seat post tube itself with either a 2nd layer of metal.. or in my case a solid piece of Oak wedged in with JB weld. ! :wink:

It's hard not to mess up the pedal space required for your legs with extra brackets.. but a picture of your idea would be welcomed !
 
That sounds like a very good idea... all I can say about the inside of the seatpost is that I was was going to check if a 9V battery fits inside, in which case I was going to fit a movement alarm in then lock it into the bike because the the backend is accessible...
trouble is with my GT bike, the seatpost fixture is an advanced design which looks really good but it's made out of a folded moulded triangle of 1mm aluminium so I'm a bit worried about putting extra weight on, especially for bumps...
 
zzoing said:
the idea is basically to fasten 1 straight pole to each side of the horizontal top tube, that go past the seatpost
Click to expand...
Flat plates might provide more strength with less intrusion into the rider's legspace.
:?:
 
His avatar shows his idea.

But it's really little different than placing the batteries in or around the center triangle. My solution was to construct a battery holder that I place over the top tube of the triangle, which I'll post pictures of in a day or two. Mine's compact and easily removed (gravity and velcro hold it on) but it requires a straight top tube, which few full-suspension bikes have. (My current bike is a hardtail.)

This long-lateral-tube idea is similar, but it can be made to work with bent top tubes and the part that sticks out rearward would double as a great mounting point for a taillight and any other lights or signals you'd want there. Also you can make them narrow. The idea is a good one but should be tested with empty tubes pre-conversion to make sure the back doesn't bump into anything and they don't obstruct the rider's legs.
 
I've seen something like this done, rods that went from the front to the back, poking out both ends and on them were baskets. But this was a DF frame, not one of those mtb like mechanisms.
 
For heavy loads seems to me a design with a little give would be better. That could cause some strangeness with how the bike feels and handles, a suspension bike with a suspension rack. Maybe that would be a problem so you'de probably have to limit the give to a small amount. But other than that issue, theres no real need for that part of the bike to be so rigid, unlike the other parts..

The grass must bend, when the wind blows across it.
 
Yes spring steel, or maybe a linkage suspension setup like the thudbuster. But different. Heck I bet even the chopped up garden hose I see some of you use would knock the peak stress way down at the seat post clamps. So its not just for your bat's health! Point is to spread the load out over time just like a suspenson fork or whatever.

Who knows, if you tune it right maybe it will improve the handling of your bike.. a la renault F1's mass damper system that the FIA outlawed for no good reason.

http://ecsurf.com/renault-mass-damper.html
 
it seems that the best material for tying racks to a bike other than having a perfectly moulded solution with rubber and so on is by winding round 100kg /4mm nylon rope, which spreads the the load evenly and doesn't dig into the frame...the thing with a suspension bike however is that all the space which is the best for the battery is taken by the spring system.
 
Vanilla, you mean some people use garden hose on the carrier post clamp?

check this I'm opting for a better solution, it's a bit obvious, with basically a spring or latex tube applying in 11kg upward force to the battery, because my gt idrive seat post mount looks like it would get worn out fast with 10kg pulling on a lever in cross country.

I'm not sure, maybe I could make the bracing poles out of fibreglass and use them to do the flexing, I want to tie the base of them with nylon, it's good when you fasten the nylon knots with pliers they are pretty strong, and also for the springy bit at the top there is also the choice in between various materials but I just really don't know what to use yet, I would love some suggestions...

:p
 

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good point-there would have to be plenty of scope for lateral movement. difficult thing seems to be how to arrange a compact variable spring system that puts just the right amount of springiness into the system...latex resistance-tubes can be made to measure, and I have also found some trampoline springs that are the same width as the battery so I did this design which is completely mental! :wink: haha
 
Elastomers may work as well as springs. Something very progressive rate that will be soft on the small bumps, but wont ever bottom out. Springs tend to be strait rate dont they? I had in mind a pivot where the welded joint normally is, with a little cushion or spring.. in red here, with the purple dot being the pivot. Well you would have it mounted up higher up than pictured for tire clearance.
 

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That will not work with the suspension. Look at the hinges -- the two parts of the swingarm rotate around a hinge near the axle so you cannot use anything that connects to both. Also, rear suspensions are not linear like a front fork suspension -- the rear wheel always rotates around a pivot usually located near the bottom bracket.

You can technically get a rear rack to work with a full-suspension bike if you're willing to do a bunch of fabrication. I've attached a simple MSPaint of a common bicycle suspension system -- red circles are pivots. Also attached is a possible rack solution -- it requires four pivots of its own. Also, it will not remain level -- as the rear wheel lifts up, the rack will end up tilting back a bit due to the shorter radius (in this picture at least) of the arm attached near the seat tube.

I wouldn't recommend this though. I wouldn't recommend any rack attached to the swingarm; I think that's just asking for trouble.
 

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that would be decent, it would be nice to find some air based padding also like industrial strength bubble wrap to make a cushion for the battery to give extra absorption. here is a picture of the seat post bracing, it's hollow and you can see how thin it is, that's why I definitely would like some extra reinforcements for the rack.
 

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It sounds like a lot of truble to try and attach the rack to the seat post with the suspension. So I was thinking why not try something like this.

Just attach the rack to the swing arm with triangle bracers in the corners for strength.
 
I wish I did have a bike like that because it would be a lot easier to put in extra bracing for the seat post rack, as shown by the green line. there is also an illustration of the suspension on the GT I drive... much less space for manoeuvre... although I am considering this diagonal bracing option if I can somehow fit it in.
 

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Ibekt- indeed that is a good solution, it is the best one for strength, although it means that the back of the bike is very clunky and unresponsive and the battery gets quite a lot of bumps and bashing, it's also quite hard to fix something that can take all that weight when the battery pulls from side to side in turnings and up and down. it's pretty good, I've actually been using that up till now with a modified basic carrier rack but it's finally cracked after three months with a fairly basic iron rack and I am tempted to try something new. really the back bounces up and down quite heavily with the battery attached to it, a bit like a basketball...-to be precise that way my bike actually had 16 kg extra fixed rigidly to the back wheel including the hub. it feels like the back wheel is square when you go over bumps.!
 
axiom makes one for double suspension mtb
http://www.axiomgear.com/product/racks/rear_suspension_racks/product.php?id=137
i took this idea an applied it to my normal rack and it works
 

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ibertk, hat would work except for the middle rod which cannot extend down to the bottom bar of the swingarm. But if it was only attached to the top one, like the other two rods, then that would be OK, sort of. But it would not be stable, it would stress the suspension, and the battery pack would not be suspended at all. Remember, the wheel is NOT suspended; the frame triangle is. In that design, shocks from bumps would transfer directly to the battery case.

Of course, batteries have no moving parts so vibration and shock really shouldn't ever cause problems if they're not being directly struck (and thus deformed). But it would stress the suspension, and the inertia of the pack would increase unsprung weight even more, limiting what the suspension can do and increasing the odds of the wheel jumping up off the ground.
 
Well if you are set on having the rack mounted to the seat post/frame and not the swing arm thee are a few examples on the forum of people who did it.

Ypedal did a double rack system that looked good (see thread)

http://www.endless-sphere.com/forums/viewtopic.php?f=4&t=1711&st=0&sk=t&sd=a&hilit=rack&start=45

Mark_A_W also did a double rack system his first attempt failed but the second used 3mm aluminium plate reinforcements (see thread)

http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=1533&p=54337&hilit=+two+rack#p54337


You could use one of these ideas or fabricate your own rack system.

If your frame is made of aluminum then it gets more difficult unless you are experienced in welding aluminum.

Here is one possible way to make your own beam rack support using flat plates (some welding required) :mrgreen:
 

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