5083 material 4043 rod
What type of aluminium are drop outs made of ?
I had thought about using those two holes, but it's a lot of force to put through two M5 bolts. I don't think they'd take it.
The bolts dont take the shearing load though, the bolts act in tension only, the shear reaction force is provided by the friction between the shim and dropout. Mill it flat and bolt&glue the shims on, you could even mill some grooves into it and matching ones into the shims. You could even wrap it in epoxy and s-glass or CF.
I am not a mechanical engineer (but I still think its a better idea than welding).
The bolts dont take the shearing load though, the bolts act in tension only, the shear reaction force is provided by the friction between the shim and dropout
This succinctly describes what I was trying to say.
But I'd still buy a new frame.
or drill out the dropouts to 12mm or larger, and mill the shim to fit into that, you only really need a 4-5mm hole for the QR, so thats quite a solid bit of metal, you could even raise the rear end by 2-3mm to allow for even more metal in the dropout. Might need a custom disk from hope to suit though.
I just went out to measure the exact dimensions of a Rohloff axle on Mrs MTG's Kona Big Unit and looking at the sliding dropouts on that, combined with your idea, thisisnotaspoon, I think I may have another solution.
The Kona dropouts fit within the width of the frame, more or less as I need to do on the tandem.
They also put the axle below the level of the actual frame dropout.
It's hard to describe in words, but I'll have ago;
Cut a new dropout from 13mm steel.
Machine 8mm of it away from all except the axle slot in the frame. It is now a 5mm plate with a 8mm thick boss on one side. This will locate it and support the weight.
Bolt it to the frame using those two M5 holes. This will also locate it and keep it in place with the wheel removed.
Cut a 10mm slot below the 8mm thick boss to take the Rohloff axle. This will raise the rear end slightly to match the longer suspension forks I will be using. If I get it right, it also means I can use a 180mm disc adapter with a 200mm disc.
In fact, thinking about this a bit more, I could probably fabricate this in steel myself.
I'll make another cardboard model to show you what I mean.
A very rough mock up here.
Imagine the cardboard is 5mm steel and the bolt head is a 10mm steel bar welded to it from the back.
Now imagine the slot is the correct shape to take a Rohloff OEM1 axle plate, like this;
This could well be the cheapest, easiest, strongest option.
No risk of weakening the frame.
No burnt paint.
If I make my plate big enough to reach the caliper bolt holes, then it acts as a shim for the caliper adapter and transfers the torque reaction of the Rohloff hub to the caliper mounting. In fact, it will even reduce the torque load as it will be further away from the centre.
A similar question has just come up on another thread.
This is more or less what I'm planning on doing.
So - you're only going to fabricate one new part and dish the wheel accordingly? Make more sense that way.
No, I'm planning on making two of them, both 5mm thick.
I just used that picture because it's a bit clearer than my description and bits of card above.
Aye - if you are moving the dropout, then you would have to make two. I was thinking of a way to resolve some of the issues with your original idea - those to do with trying to weld on thin (5mm) plate.
Here we go with a classic wooden mock up to see if it all works.
You can see the holes in the ply where the axle would originally have been. I'll be putting 10mm bolts through there to take most of the load.
The gear hanger is going to need cutting as well. I'll incorporate a new one in to the right hand dropout as I will need somewhere to attach a tensioner.
That's a 160mm brake mount on there. If I've got my measurements right, it should now line up with a 200mm disc.
The frame is sold as suitable for 26" or 700c wheels and a rigid fork, it's even got two sets of rim brake bosses.
I'll be using 26" wheels, so as the front will be raised a bit by a suspension fork, I reckon raising the rear end by 20mm should put the BB heights and head angle somewhere near right.Posted 3 weeks ago #
I'm not familiar with a Rohloff hub but could you not get a longer axle machined and use a 5mm spacer on each side?Posted 3 weeks ago #
I've progressed to aluminium mock ups.
That's a 160mm adapter with a 200mm disc, so the frame is raised 20mm.
Having measured the BB height, I have now bought a 140mm adapter and will make another dropout to raise it another 10mm.
I know it looks rough now, just hacked out of aluminium, but I think once I've tapped the axle holes to 10mm and fitted the bolts to clamp it to the frame, it will be strong enough for a solo test ride.
Then when I'm sure it works, I'll cut them out of 5mm steel.Posted 1 week ago #
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