mounting 7kg of battery on a full suspension frame..

[nonlineartom]

I've put 1,500 miles on my commuter bike since March, it was a £50 rubbish deathtrap to start with so I've retired it to be replaced with a Saracen Raw 2 mountainbike, I got it because it was very cheap, hydraulic brakes, deeeeeeep dropouts and a nice big flat mounting surface to epoxy on some torque arms. I am however now faced with the dilema of how to securely mount 7KG of LifePo4 battery that will handle harsh potholes and big speed bumps. The old bike was a hardtail so a £20 pannier rack was all I needed, it clattered around a bit but with 3 elastic luggage straps it was never at any risk of going anywhere. Here is the bike in question



This was from when I took it for a nice test ride over the moors with the battery pack in a rucksack, this isn't practical for commuting as I need to carry a rucksack full of work stuffs. I've used a Topeak beamrack before as the battery lives inside a Topeak DX pannier bag with the quick track system, it just fits in and keeps the weather off it. I've used a Topeak beam rack before rated for 9KG and after a month the QR bolt snapped as I predicted. I've bought a cheap seatpost pannier that mounts with 4 bolts but the topeak bag doesn't sit very well on it at all and wobbles around, there is also a clearance issue because there is 5" of travel in the rear suspension a big bump means the tire scrapes on the beam, has anyone else had this problem and found a solution? Open to ideas.

 

[nonlineartom]

 

[neptronix]

*cough* RC Lipo *cough*

 

[nonlineartom]

I've seriously considered it, BUT it's just not practical, I need to be able to just roll this into the garage, plug in a single lead and roll it out in the morning ready to go. I'm using LiPo on my "fun" project(s) but I need the stability of LiFePo4 and the BMS for this particular project. I don't have the skills to split the pack in two to hang either side of the top bar either. This 36V pack has approximately 200 full cycles on it being used at 2C everday, it's delivering 12AH before hitting LVC but that's enough for my commute with a bit spare incase I take a detour or whatever. So thanks for the suggestion but I'm going to have to rule it out as not being sensible for fire and forget everyday commuting. any other bright ideas?

 

[dumbluck]

handle bar basket

 

[neptronix]

NiCoMn pack then? ( even smaller than lipo actually )

http://www.bmsbattery.com/36v/165-36v-15ah-lithium-ion-electric-bicycle-battery-pack.html

OK now i have not tested or seen any reports of these batteries yet. But their capacity per weight actually trumps lipo.. and it may actually fit in your space too.


Anyhow mounting batteries is the hardest part of this, especially on a dual Suspension bike that doesn't lend to having much triangle space.

Maybe a topeak rear rack + some kind of extra support hanging off some part of the bike .. ?

 

[geetarboy]

You might consider an 'Axiom oddysey' rear rack designed for full suspension bikes. I have been using one for over a year now and carry 12+ lbs. of lipo on it and have had no problems with it.

 

[circuit]

You might consider an 'Axiom oddysey' rear rack designed for full suspension bikes. I have been using one for over a year now and carry 12+ lbs. of lipo on it and have had no problems with it.

Used it with 6,5kg battery. After a couple of months simply snapped off. Battery went down and smashed into ground. Expensive failure, almost squeezed a tear.
The only way to make things right - make a custom frame.

 

[dogman dan]

I've bent or broken several racks and seatposts.

But never had any problems when I did this.

I have loaded 50 pounds on this rig, and ridden 60 miles. About 4000 miles on it to date with no problems, always carrying about 20 pounds. But a lot more after going to the grocery or hardware store.

 

[nonlineartom]

I like what you've done there, is that bits of an old BBQ in there or something? Whatever works right!

I'm leaning towards getting this....

I used to have one just like it without the kink in on my old bike, because there is only one bolt holding it to the seatpost the battery bag would wobble just a little bit, enough that after a month of riding through pot holes the QR bolt just sheared in half which was messy. I think the problem was possibly because I had to use the largest rubber shim as it was a narrow seatpost and the rubber compressed slightly making it wobble. If it was joined with 4 bolts like most cheap racks I don't think there would have been a problem. They are rated to 9KG but I've proven with no less than 3 Topeak racks that their ratings are absolute lies.

 

[marty]

http://www.oldmanmountain.com

 

[geetarboy]

You might consider an 'Axiom oddysey' rear rack designed for full suspension bikes. I have been using one for over a year now and carry 12+ lbs. of lipo on it and have had no problems with it.

Used it with 6,5kg battery. After a couple of months simply snapped off. Battery went down and smashed into ground. Expensive failure, almost squeezed a tear.
The only way to make things right - make a custom frame.

Hey Circuit, I don't recognize that. Doesn't look like the Axiom rack I have. The one one in your picture looks like it mounts to the seat post. The one I have is set-up almost identical to the 'oldmanmountain' on in Marty's picture.

 

[gensem]

Everytime I see thoses "flying" racks hanging over a thousand of dollars in battery, freaks me out...
You got have 2 point to fix the rack, otherwise it ll break, sooner than later.

 

[dogman dan]

And use the axxiom, or equivilant. Notice one QR bolt on that other rack, and 4 stout allen bolts on my axxiom?

The brace is 1/2 steel electric conduit. But anything stout would work fine, angle or aluminum tube. But the conduit is easy to work with. just cut, pound the ends flat, drill. Downside is you may not be able to adjust the seat anymore.

Here's one I didn't get around to installing the brace in time. The battery was fine, inside an aluminum box, inside padding, inside the bule steel box.
Riding home one handed, standing up, with the battery in the other hand was difficult.

 

[gensem]

If you are not in a budget, this is the rack I would recommend. Warranted for 25kg, but pricy!

http://www.freeload.co.nz/store/0/4/Tour-rack

 

[Nanoha]

I have tried both the axiom odyssey and the freeload rack on my full suspension but they both sway too much side to side and the weight is not suspended so gets subjected to all the bumps and vibrations.
So far I think Karma has a good solution where he cuts the beam and sticks a solid rod in one end then a handlebar stem on the other: http://endless-sphere.com/forums/viewtopic.php?f=3&t=11704&start=15

 

[Spicerack]

How about in cages either side of the top tube. I'm putting three packs on to my bike, one either side of the top tube and one infront of the top tube. As long as you have clearance that is. I certainly don't like the idea of all that weight hanging off the back, or adding to the unsprung weight of the rear wheel.

I'm adding 15kg batteries to mine, to get range and it looks like it'll fit quite neatly.

I'm using powdercoated kitchen tidy frames- used for spice racks or something originally!

 

[dogman dan]

Re the axxiom rack, the one I showed is suspended, that is, it's weight is not on the swingarm but on the main frame. Sway from side to side is a big problem with any heavily loaded rack, even on a hardtail. I found the braces I add to mine greatly reduce the side sway of the rack. The trick is to install the braces, then scrunch the rack down as much as possible on the seatpost so the weight is on those braces as much as possible. This helps a lot with rack sway, or the tendency for it to simply slide to the side on the seat mount. At that point, you may find that your frame is inadequate, and you'll see a lot of wagging the tail when loaded really heavy. On a wallbike, the frame will be seen bending alarmingly!

If you are using lipo, then it does indeed make a lot of sense to just build saddlebag style boxes for the top tube. Even for a bike with a triangle, it may be too small or awkward. So the box on either side may work best. up to about 6" wide, it's suprisingly easy to get used to pedaling a bit bowlegged.View attachment 1

If you need to carry a largish ping, and have a bike with no triangle, then the rear rack may be nearly the only option.

 

[darth_elevator]

....never had any problems when I did this.View attachment 1

.... The brace is 1/2 steel electric conduit. But anything stout would work fine, angle or aluminum tube. But the conduit is easy to work with. just cut, pound the ends flat, drill....

Dogman Dan, I realize this post is pretty old, but I'm wondering how you attached the electric conduit to the rack. Did you drill a hole (or use a pre-existing hole) in the rack and simply bolt the conduit to it, similar to how you attached it to the seat post? I am thinking of building a support similar to yours, as my seatpost snapped today, similar to the picture you posted above.

 

[TotalConfusion]

My rear rack on my Specialized Dual Suspension was quite easy to do and can hold me sitting on it with 8mm bolts screwing it to my torque arms.

 

[darth_elevator]

My rear rack on my Specialized Dual Suspension was quite easy to do and can hold me sitting on it with 8mm bolts screwing it to my torque arms.

Wow, that looks great! I like the idea of not attaching to the seat post at all. Takes broken seat posts completely out of the equation. And I also like how your method puts the weight quite a bit lower -- on mine, I originally had the rack mounted down right where the seat post exited the frame, but the rack would hit the tire whenever the suspension bottomed out, so I had to mount it up a lot higher on the seat post.

How did you attach that custom metal piece that comes out of the front of the rack? As you can see from the picture, I have some room to attach right in front of the brake on the horizontal bar on the pivot point.

And did you drill the mounting holes down on the forks or did you use existing holes? My forks unfortunately don't have any small bolt holes, but maybe I could figure out some way to attach to that triangular space.

 

[kfong]

Using a rear seat post rack is a bad idea. I went through 3 of those seat post racks. I made it strong, but the frame ended up breaking due to the stresses I put on from trail riding. You can see where the frame broke.

http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=12654&start=125

If you do only street riding, and avoid jumps and potholes. It would be possible to use these types of seat posts. To make them last, throw out the original bolt and use a quality hex bolt. Plug the seat post end with clay and pour epoxy mixed with fillers(sand, micro balloons, ect.) into the open end. Fill about half way. Adding a triangle brace made it even stronger. Going with a frame mounted battery was what I ended up with. I had to loose out on capacity, but gained reliability and better handling. My trail rides are brutal on the bike, but the frame mounted pack has lasted these past years with many crashes and jumps.

Totalconfusion rear rack would be a better approach. This is what I use for my hard tails, if you can add a pivot on your setup.

 

[darth_elevator]

....Going with a frame mounted battery was what I ended up with. I had to loose out on capacity, but gained reliability and better handling. My trail rides are brutal on the bike, but the frame mounted pack has lasted these past years with many crashes and jumps....

Kfong, I'd love to see some pics of your frame-mounted pack. I would very much prefer a frame-mounted pack, as I hate all that weight on the back of the bike, as well as having the weight so high up from the center of gravity. Losing the triangle battery bag was the only thing I regretted about switching to a full suspension.

The first picture below is my bike. As you can see, besides the rear rack, it looks like I'm limited to three other spots: on top of the frame (in between the seat and handlebars); under the frame (in front of the bafang); or on the handlebars. The other pics are installation ideas that might work with my frame.

View attachment 4

 

[TotalConfusion]

My rear rack on my Specialized Dual Suspension was quite easy to do and can hold me sitting on it with 8mm bolts screwing it to my torque arms.

Wow, that looks great! I like the idea of not attaching to the seat post at all. Takes broken seat posts completely out of the equation. And I also like how your method puts the weight quite a bit lower -- on mine, I originally had the rack mounted down right where the seat post exited the frame, but the rack would hit the tire whenever the suspension bottomed out, so I had to mount it up a lot higher on the seat post.

How did you attach that custom metal piece that comes out of the front of the rack? As you can see from the picture, I have some room to attach right in front of the brake on the horizontal bar on the pivot point.

And did you drill the mounting holes down on the forks or did you use existing holes? My forks unfortunately don't have any small bolt holes, but maybe I could figure out some way to attach to that triangular space.

View attachment 4

Your bikes rear triangle would seem to be quite simple like mine was, I used Narva Electrical C clamps to rap around my pivit point like in the photo.

I drilled straight into my torque plates i made up for the bike with a 8mm thread, the hardest thing to do that i needed help with was to turn the m12 thread down to a m8 thread half way along the m12 so the M12 would be a tight fit in the rack mount.
I find putting alot of weight on the rear rack doesnt ruin the handling at all apart from jumping which is expected when you have 8kg of motor and extra on the back

 

[friendly1uk]

I've seriously considered it, BUT it's just not practical, I need to be able to just roll this into the garage, plug in a single lead and roll it out in the morning ready to go.

RC LiPo is a cell chemistry, not a method of charging. I realise the mere mention of it gets modelers straight into the conversation with their modeling chargers, but that does not make it right. Use whatever cell chemistry you like, with a bms, like any manufacturer would. We are not modeling.


Perhaps you could keep the pack in your bag and put your work stuff on a post mounted rack. I'm sure it weighs less than the 3kg I would personally put on such a rack. That would get you going until you fabricate something.


I notice many rack users put them high up the post and move the battery right back like they are trying to bust it or do wheelies. The rack should meet the post as low as possible, and the weight should be as forward as possible. Under the seat if possible. Then the rack would carry double and the bike would handle better. Many times I have looked in a rear bag and found the controller near the post and cells toward the back of the bike. Just turning the bag around could be worth 30% more load carrying capacity.


Perhaps a snapped rack could be hinged, allowing the rack to them drop some supports down to the rear axle area. I have seen hinges for poles uses in pram covers. The pram covers on the back of boats, where poles are often that kind of size. There are many rod ends that would do it. http://decor.basicq.com/cgi-bin/dcart/scan/fi=products/co=yes/st=db/sf=prod_group/se=Elbow/op=eq.html