Lightning Rod Big Block, Luna Cargo, Rohloff and Torque

[ixandstones]

Well I've hit a snag and need the input of some experienced builders.

I've recently finished building a luna cargo fat bike with the LR big block, powered by the 60v, 25ah Luna Battry and the Lyen 65 amp controller. Had a 52t front crank going to the LR big block and 16t to 16t Motor to rohloff sprocket ratio.

I had bolted the Torque axle plate of the rohloff to the rear dropouts of the frame (no room for torque arm).

I went for a long test drive today, by the time I came back the rear dropouts of the luna were completely bent out of shape due to the torque plate of the rohloff. Had I ridden a few more miles I probably would have had a huuuge accident after the rear wheel left the bike.

I bent the dropouts back into shape (took lots and lots of effort) hopefully they are not cracked or terribly weakened. I ordered the rohloff monkeybone and corresponding axle plate. But I am wondering if the sheer power that can bend those beefy forks as much as it did, will not simply snap off the disc brake bolts.

My questions are the following:

-Anyone have experience with the monkeybone from rohloff and lots of power? Is it sturdier than what I had done before (bolt the axle plate to dropouts?
-Anything to check for at the rear dropouts that I bent back into shape? Don't want to ride a weakened frame.
-Any solution to further strengthen rear dropouts?
-Any alternative frame suggestions to replace the luna frame but keep the huge battery/motor/fat tires?

Any pointers would be great.

Thanks

 

[amberwolf]

Pics of the problem would help, both as they were right after the ride, and of whatever fixes you've already done. I didn't see any pics of that part of the bike in your other thread, just of some of the middle of the bike in various stages of assembly.

If the dropouts are bending/breaking off the frame, then it sounds like there is torque on them in a direction they weren't designed for, or they are going to need torque plates that are actually welded to the frame (if it's steel) or bolted to it or clamped around it and to the original dropouts as well, to completely stiffen up the whole thing.

 

[ixandstones]

Sorry For the late reply, hurricane Mathew preparations and stuff got me busy for the last few days.

I had not taken picks of the bent out forks, but I took a photo now. They are almost back to where they were, does not lok like it is cracked but I do not know.

Can see scratch marks from the vice grips.

I bought the Rohloff Monkeybone adapter to attach the torque axleplate to the rear brake mounts but it seems the luna frame is not up to the standards as the OEM2 axleplate and monkeybone will no align with the holes. It is a few mm off but enough to prevent from bolting the disc brake mount to the frame when the axle plate is in the rear dropout track.

So I either need to find another adapter to fit onto this frame (maybe a bmx type disc brake adapter?) or maybe drill a hole in the rear dropouts and bolt the axleplate to that hole.

Could be simple enough to drill a hole there but will it compromise the frame?

 

[Triketech]

If you're putting enough torque to the Rohloff damage the dropouts like that and the axle nuts were torqued, I suspect the torque levels are already stressing the shear pins.

I'm a big fan of IGH's but I'm not too confident on durability under power assist. Thankfully, folks like you are willing to take the risk with a little pioneering. Please do keep us informed periodically, this may be one of the best examples to follow.

Not sure which torque arm you're using, when I played with a Rohloff I had one like this.

Not powered, and mounted on a Catrike Expedition for a few months many years ago.

 

[ixandstones]

The speedbone unfortunately does not fit onto my luna cargo frame. The deep dropouts and disc brake placement make it impossible.

I am going the way of blocking the speedbone axleplate under the disc brake mount.

In the picture was the monkeybone disc brake mount since the magura mount was on the bike already, I will not be using the monkeybone but the stock magura mount.