Broken rack, Pinch flat, broken spoke

[El_Steak]

On 3 separate occasions, all in the last month...

Everything is tightly fitted on my bike so each time its half a day of work to remove the wiring, controller, torque arms and wheel and then put it all back together and try to adjust that damn warped disk brake...

The cause is obvious: lots of potholes, lots of weight on the rear wheel (24s3p of lipo on the rack), hard tail frame and maybe I'm a bit too enthusiastic in my riding. Here's the bike (after 5000km, it's not as shiny anymore):

(motor has been changed after radial fins failure)

This is my main mean of transportation to work for 6-7 months a year. When the bike is down, I have to take the bus. When the rack broke a couple of weeks ago I was stuck in the middle of my commute, had to call my father to come pick me in a minivan and missed an important meeting at work.

So until I can spend months building the nicest full suspension bike with a custom battery box in the frame, I have to find a quick fix solution to shave some weight. I see a few options:

- Go on a diet (I'm at 155lbs so not a lot of room there)
- Slow down to reduce power consumption and scale the batteries down to 24s2p instead of 24s3p (7lbs saved, but its hard not to go fast when your bike can)
- Reconfigure the battery pack to 18s3p (5lbs saved but this would be a pain to configure with my current charging solution)
- Cut the battery pack in half to 12s3p (10lbs saved, but it would be really slow, I guess under 40km/h on my 2807/24" wheel)
- Cut the battery pack in half to 12s3p and swap the motor for a faster winding: 2806 or even 2805 (Might need to go 12s4p with faster winding)

I kind of like the idea of going to 12s as this would both reduce the weight of the battery considerably and force me to slow down. It would also make charging simpler with a single Hyperion 1420i instead of the 2 I use now.

Any other ideas for a quick weight loss?

 

[fractal]

Maybe you could redistribute the weight envenly instead of having it all in the back. I did that and i think it helps. I put the pack between my legs. The handling is better also. If you go 12s3p, you would have to recharge at work? Keep one charger at work? Right now, i'm running 12s 3p because i blew a fet so I got a temporary controller while the other one is being repaired. With a 22 inch OD wheel, i get about 45 km/h at 40 amps WOT. My motor is about 9Kv. Its not exciting, but it works. You could leave one pack at home, and one at work, and just swap them. Good luck!

 

[icecube57]

there is a top tube pannier that i know ill fit 6 packs on each side and that will shift some weight up front. I have a TF bike by the way.

 

[Ykick]

I'm confused - what's new? LOL...

Why does your photo caption say no loose spokes but thread title indicates broken spoke? Broken is loose to me. Either way I can't see any obvious fault with your rims/spokes.

My 2 cents is you gotta get those batteries moved forward either over the triangle in saddlebags and/or Oatnet steering head mount. Yes, you also probably need to slow down. These are bicycles after all and even cruising between 15-20 MPH with so much weight is hard enough on wheels. 25-30 MPH is asking for trouble with every shock and jolt to the wheel assembly.

I love the TF frames but a large Trek that holds a triangle bag is probably the ideal hard tail platform.

 

[neptronix]

I've had excellent luck in potholed riding with my mid mount lipo setup & the falconEV bag. Great weight distribution and i got tired of hearing my rear rack clunk around.

 

[El_Steak]

Why does your photo caption say no loose spokes but thread title indicates broken spoke? Broken is loose to me. Either way I can't see any obvious fault with your rims/spokes.

It's an old picture from last year, the only one I had on hand. The motor/wheel has been replaced since.

 

[Sacman]

On 3 separate occasions, all in the last month...

The cause is obvious: lots of potholes, lots of weight on the rear wheel (24s3p of lipo on the rack), hard tail frame and maybe I'm a bit too enthusiastic in my riding. Here's the bike (after 5000km, it's not as shiny anymore):

So until I can spend months building the nicest full suspension bike with a custom battery box in the frame, I have to find a quick fix solution to shave some weight. I see a few options:

- Go on a diet (I'm at 155lbs so not a lot of room there)
- Slow down to reduce power consumption and scale the batteries down to 24s2p instead of 24s3p (7lbs saved, but its hard not to go fast when your bike can)
- Reconfigure the battery pack to 18s3p (5lbs saved but this would be a pain to configure with my current charging solution)
- Cut the battery pack in half to 12s3p (10lbs saved, but it would be really slow, I guess under 40km/h on my 2807/24" wheel)
- Cut the battery pack in half to 12s3p and swap the motor for a faster winding: 2806 or even 2805 (Might need to go 12s4p with faster winding)

I kind of like the idea of going to 12s as this would both reduce the weight of the battery considerably and force me to slow down. It would also make charging simpler with a single Hyperion 1420i instead of the 2 I use now.

Any other ideas for a quick weight loss?

Hi El_Steak,

Before I went full suspension I too had to deal with a lot of broken spokes and pinch flats. But I now have 2 serious commuter ebikes of similar design. Both are full suspension with the 12s8p Lipo (45V x 40Ah =1.8Kwh) batteries on rear rack and side saddle bags (panniers). As you know, the full suspension takes a lot of the load and shock out of the spokes and tires and the batteries themselves when riding over big potholes and railroad tracks. Here's one of my commuter ebikes.

My battery packs are broken down into 3 separate sub-packs. The main pack (12s4p) is on the top center of my rear rack. The other 2 smaller sub-packs (12s2p) hang off the sides of the rear rack in the saddle bags. (You and I use the same Topeak rear trunk bag so I know you know how those side bags are deployed).

Okay so how does this help you on your hardtail Tidalforce frame? Well the 2 smaller battery packs hanging off the side of the rear rack actually hang from 3 short bungee cables each. Those bungee cables provide an additional cushion and suspension to not only your side battery packs but also alleviates the shock loads to your spokes and tires.

Sorry I don't have pics of these but it's simple enough to explain. The bungee runs down one side of the battery pack, goes underneath and comes up the other side. Lots of electical tape and duct tape holds the bungee securely to the battery. There is 3-inch length of bungee and the metal hook. I cut 3 slits on the inside face of the saddle bags so the metal hooks (at the end of each bungee) can pass thru and actually hook on to the side of the rigid rear rack. Again, there are 3 of these bungees with hooks per battery pack on each side. So there you have it... suspended side battery packs. The cloth side saddle bags of the Topeak trunk bag don't carry any weight of the battery ... but just cover up those side battery packs.

 

[El_Steak]

Sorry I don't have pics of these but it's simple enough to explain. The bungee runs down one side of the battery pack, goes underneath and comes up the other side. Lots of electical tape and duct tape holds the bungee securely to the battery. There is 3-inch length of bungee and the metal hook. I cut 3 slits on the inside face of the saddle bags so the metal hooks (at the end of each bungee) can pass thru and actually hook on to the side of the rigid rear rack. Again, there are 3 of these bungees with hooks per battery pack on each side. So there you have it... suspended side battery packs. The cloth side saddle bags of the Topeak trunk bag don't carry any weight of the battery ... but just cover up those side battery packs.

Thanks Sacman, thats a very clever idea, adding suspension inside the battery bags. I might have to lenghten my wires though to ensure they don't unplug on a nasty bump. It would be easy to implement with my bike, the pack is split in 2 "modules" of 12s3p, one in each saddle bag. The batteries are inside a protective box that could easily be wrapped with bungy cords. You can see one of the box on this picture:

 

[Sacman]

You can also use other elastic things instead of just bungee. For instance (since you already have a wooden box enclosure) you can also strips of old black rubber inner tube staple gunned to the side of your wooden battery boxes.

 

[dogman dan]

Though the mongoose blackcomb suspension is a joke, it works well enough to prevent broken spokes, even when riding over rocks all the time on my dirt bike.

Moving the batteries to the area just behind the handlebars is what you really need, on the mongoose too. But if you pedal a lot, I understand the reluctance to have an 8" wide battery to pedal bowlegged around.

It's a dilemma, and why my commuter is front hub, despite the huge can of worms that opens up with alloy suspension forks.

The best solution for it I have found yet, is the bike that loves a load on the rear. Took quite a while to find an all steel cheap suspension bike to weld the front frame. When it's time to carry, I got the bike now. Full suspension longtail, muahhhahaha

 

[amberwolf]

Alternately, you could move the battery (or some of it) to a box mounted to the headtube just between the bars and the top of the fork. Mounted to the frame itself it wont give you any steering problems, like it might if mounted to the fork or bars.

Even mounted to the bars/fork is not so bad if it's really close to the pivot point. The farther out it is, the worse the levering action is, and the more steering issues you might have. (I have a fair bit of recent direct experience with this the last couple weeks, hauling various loads in front baskets, some of which cause no problems and some of which made me lose the bike to a tip-over).

Either one will help save your wheel and rack.


The rack problem can also be helped by side-to-side triangulation, if you can do it and still clear the wheel. Probably not, from what I can see. The side-to-side wiggle contributes to flex-caused fatigue failures, in my experiences. I'm expecting the rack on my Fusin test bike to begin showing failures any time now, but I havent' seen them yet. Might take a couple hundred more miles to start showing up since the rear wheel does have cheap suspension on it, but the rack is actually on the swingarm, which greatly reduces it's effectiveness--it's still much better than the bikes I've done this with that had NO rear suspension.