My cube e bike is a 148 thru axle so the normal qr skewers with the bobbins on the end will not work.  The bike has seatstay mounts for a rack.  I have altered some bobbins so they have an m5 male thead to screw into the rack mounts.   My worry is that its only m5 not m6 and that the bobbin will have little support behind it.  I have successfully done similar in the past which worked fine but the bobbins were bolted onto a tubus rack with m6 bolts and were better supported from tbe back bolting onto a flat plate.

If it fails i assume the failure point would be bending or breaking the bolt.  I don’t want to risk knackering the frame.

Thoughts / opinions / calling me a fool please😀

I can get a axle to do this but from the US and expensive

Sugru or similar to provide more support under the bobbin?

Right at the weld ?. Bad idea.

I wouldnt think they had pulling a weighted trailer in mind.

I wouldnt fancy that, the risk reward doesnt appear to stack up. Would one of these be the correct answer? I imagine there are cheaper alternatives out there.

Thru Axle

I wouldn’t do it with that small a bolt and thread, or on that bit of the frame. I’d stick with using the proper axle.

Will it really twist more than a frame in a turbo trainer? Or the twisting from the disc brake? What are you pulling in the trailer? If it mounted both sides I think I’d be happier. I had a Burley piccolo tagalong that mounted to a special rack. I’d use a longer bolt with support THROUGH the dropout and a nut on the other side to lock it in place.

could you use a longer bolt to allow the load to be taken evenly on both sides? I don’t really know what the trailer mount looks like

I’d get the axle rather than risk that

Tj message me with what you need, I have a Robert project trailer axle here doing nothing, yours for a donation to edale MRT if it fits

Get th3 proper axle, otherwise there’s a reasonable chance you’ll wreck the frame or lose th3 trailer (hopefully without kids in it).

the trailer mount is a fork that slips over the narrow part of the bobbin ie puts the load 15mm or so out from the amount.  I doubt a nut on the back would make any difference – the bolt goes thru 10mm of thread

there is a bobbin on each side of the bike.  Its a bob trailer

bikerevive – PM sent

Most of you seem to have the same doubts I have.If it were a 6mm bolt and a flat area behind to give support I would not worry as I have made that work before with the bobbins bolted to a rack

If there’s one either side it should be no problem i.e. the bob mount is basically a rotated pannier rack.  The ‘nose’ weight of you trailer will be nothing compared to a rack. I think most people above are concerned that it was going to a single mount in which case the levering forces would be a bit dodgy.

I’ve bought a longer Robert axle project axle, cut the end off and rethreaded it before.

To be clear there is a bobbin each side – the trailer yoke hooks over the bobbins.  Load will be mainly straight down at half the weight of the trailer but will also take fore and aft loads from hitting things and accelerating.  Its the bolt bending or pulling out of the threads that I think will happen but I amconcerned the levearge might damage the frame

I do like a bodge but that’s no from me I’m afraid. Empty trailer cutting about, probably ok. Weighted I would be unhappy. Cost of failure = 😭

Buggeration.  I was hoping you would all tell me not to worry 🙁

At least from this I have found out you can get the correct axle in the UK so ta for that

May be the most likely failure mode would be that the bolt breaks.  If this happens   on tour  it could be problematic as you need to find someone competent to drill the remains of the bolt out, and not be able to tow your trailer until this is done.

With rack bolts I have seen bolt snapping happen to others  when the bolt gets a bit lose and allows the rack to bang up and down against the bolt.

I would be concerned about the bolt having a smaller diameter than the bobbin.   This might be mitigated if the bolt supplies sufficient pressure to stop movement at a torque which is appropriate to the threads.  I would suggest using a torque wrench and getting advise on a safe torque for the combination of harness of thread of bolt and frame and length of thread.  Safe torque should take into account of lubrication of threads.

You would want to choose the right grade of steel for your bolt rathe than using a random one, and consider using Loctite and/or a antivibration washer (I find them very effective on rack bolts) to ensure it does not loosen and allow movement between the bobbin, the frame and the bolt.

(PS I am not a mechanical engineer  hence I start my answer ‘may be’ and do not suggest a safe torque. )

Tim

? Is this the same thing (*effectively) as Robert’s (but cheaper)

https://www.topeak.com/global/en/product/1149-JOURNEY-TRAILER-TX-AXLE-KIT-P10

nearly but not quite unfortunatly

Look at tapping the through axle? Assuming it’s hollow.

Edit: in response to anti vibration washers, star washers or similar work ok if the parts on either side are soft enough for them to bite on to but spring washers do nothing once they are compressed – they effectively turn in to flat washers.

Look at tapping the through axle? Assuming it’s hollow.

Nice idea  and the hollow centre is a perfect size but its a 5mm allan key fitting on the end would get wrecked.

One option to avoid potential frame damage would be to swap the bolts for nylon ones that will snap before the frame does.
Might want to do a few test trips before committing to a long tour but should be strong enough in normal use but will break in a crash or other mishap.
Edit: is another option to thread a long rear wheel skewer with the trailer bobbins on right through the thru axle?

Didn’t Edinburghbike do a knockoff of the Bob trailer? Do they not have anything suitable.

Stress from a Bob trailer is a lot more than a 2 wheeled one. And I bet you ride faster / with less sympathy than you might with a conventional trailer.

If my bodge will not work then the proper axle seems the right thing to do.  From this thread sjs have them.

You are right.  The bob gets hammered as I ride with it offroad.  Been off a 2 or 3 ft drop with it and hammered over rocks