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Here we go with a classic wooden mock up to see if it all works.
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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.
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?
I've progressed to aluminium mock ups.
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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.
Have you considered an adapter that cups the existing dropout so that the load is transferred by contact on all possible sides rather than through the welded patch and/or bolts?
MTG you should speak Ben @ Kinectics cycles. He modified a Rolhoff hub for TJ to fit in his tandem.
If I remember right it involved spacing out the the hub rather than spacing in the frame. The advantage would be that you could fit a standard tandem hub if you wanted to at a later date.
Still experimenting, this will probably not be the final design.
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Anga, the load will be carried by the M10 bolts where the axle should be. The M6 caliper bolts and M5 rack bolts are just for location.
Bikepawl, I think Ben replied on another thread and I've seen what Jeremy has done, we are in contact via Facebook.
He put a 10mm spacer on one side of the hub, which means he had to dish the wheel to suit and make a 10mm spacer for the caliper.
I think my solution is neater. No extra spacers for the caliper or gear hanger and any 135mm hub wheel, Rohloff or derailleur, will drop straight in.
One disadvantage of the above design, apart from lifting the back end of the bike a little too much, is that the chain is now too close to the chain stay.
That's a 140mm adapter, so I think I'll go back to a 160mm, which will drop the frame, or raise the axle, by 10mm.
It's starting to look like acomplete tandem now.
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Can the rohloff hub itself take the extra torque and weight of two riders?
There have been reports of failures i think...
http://www.cyclechat.net/threads/another-rohloff-tandem-hub-failure.51658/
Is that a 6 pot caliper?! Never knew hope made brakes with that many pots.
My suggestion was in the context of the idea in this [url= http://singletrackworld.com/forum/topic/what-type-of-aluminium-are-drop-outs-made-of#post-5722405 ]post[/url]
I can confirm that Yeti drop outs are made of cheese...
HoratioHufnagel, I am aware that Rohloff hubs are not as reliable as Rohloff themselves would like everyone to believe.
Their warranty service is pretty good though, it seems to be unlimited by age or mileage and free, apart from the £12 postage costs via the LBS.
maximusmountain, Mono 6ti, Mono 6 and Moto 6, as dicussed here, http://singletrackworld.com/forum/topic/hope-6-piston-brakes-much-better-than-4
Anga, I've given up on the welding idea. I think what I'm doing now is the easiest, neatest and cheapest way round the problem.
Welding is not required--you can bolt at a couple of places.
Think of a shoe or glove--insert the dropout into the adapter and bolt it into place. The adapter cups the dropout. The axle goes through the original dropout--I am assuming you can bolt it into place.
Can the rohloff hub itself take the extra torque and weight of two riders?
Yes - I've only seen one break in more than 10 years, that was an early one on a tandem which snapped a flange. They since beefed up the flanges.
I see what you mean now, anga.
Yes, that is one idea I had considered. If I wanted to keep the axle in the original position then I would have to do something like that as the Rohloff axle only extends 6mm beyond the locknuts, so the weight would be almost entirely on the dropouts I have made and they would need some sort of strong support.
A bit of a quickly bodged mock up, but something like this, except I would use bolts or welding, not molegrips.
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Trying out different dropouts and fork lengths, I'm getting BB heights of between 340mm and 390mm.
Of the few tandem frame manufacturers who post their geometry on line, it looks like 270mm is about average.
[url= http://www.ventanausa.com/bikes/el-conquistador-de-montanas/ ]Ventana is the one exception, at 343mm/361mm[/url], before sag.
Tandem Jeremy's is about 370mm as well, allowing for sag, so I'll stick with what I'm doing for now, as it's easier, although if it does feel too tall, I may yet go for your idea, anga.
It's starting to look like acomplete tandem now.
It's starting to look like a complete * ** ** of **** now.
What I would do in this situation is to make one 10mm thicker righthand dropout to replace the existing gear hanger. An exact copy secured in the same way, except thicker. The 135mm wheel would then sit 5mm offset to the left in the existing left hand dropout. The 5mm offset to the left would make no discernible difference to the bike (i've seen plenty of standard bikes worse than this), but you could re-dish the wheel if you were really bothered about it. Everything will then fit and work as normal, and loads will be fed into the frame as they were intended to be.
Took your picture and made minor changes. The dark areas (some of which may be mechanically impossible or not useful) support the dropout and transfer force. You can also use a larger bolt(s) in one of the shaded areas for support. Welding may not be needed.
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i would make the new pieces out of steel which will be so much stronger than aliminium.
Remember this thread ?
We've done a few miles on the 5mm aluminium dropouts now and they haven't bent or broken yet.
They are still a bit rough looking, and I'm still not sure whether to just tidy them up a bit, make them in 5mm steel, or make them in 6mm aluminium and spread the frame 2mm.
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I'll be swapping to a simple pull up tensioner. It's only a 13t rear sprocket, so I want to get as many teeth engaged as I can.
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That's a 200mm disc, I'll be fitting a 205mm to line up with the caliper better.
Caliper, Rohloff and pannier rack all clearing each other nicely.
Fork travel reduced to 105mm for better stand over clearance.
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It's all a bit of trial and error experimenting at the moment, with things like out of phase cranks, 22t primary chainrings and exposed Rohloff cables.
out of phase cranks
Is this to reduce the peak load on the drivetrain?
Looks good!
Not specifically, although that should be a bonus.
There's a huge thread on the subject here, http://www.bikeforums.net/tandem-cycling/267643-poll-do-you-ride-phase-out-phase-do-you-like-better.html
In short, most people stick with In Phase, because it's the "standard" set up.
Of those who try Out Of Phase, it's about half and half either prefer it or give up and go back to In Phase.
Some go the full 90 degrees, but that's not practical for an off road tandem.
Putting the stronger rider ahead is the most common arrangement and it seems to be better for us, it definitely feels smoother.
It was one quote in particular from that thread that got me interested;
...the bottom line for us is a 5% increase in average speed for the same cardiac output in favor of OOP
First long ride today and it brought a problem with the drop outs to light.
You can see in the pictures above that they are attached to the frame with M10 bolts threaded in to the drop out.
Not surprisingly, the bolt on the chain side, where there is most strain, pulled out of the 5mm thick aluminium, allowing the drop out to move slightly, resulting in the tyre touching the chainstay.
I've modified it now by using countersunk bolts and dome nuts.
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Graham.
Not meaning to offend you but please stop all these shitty bodges that are never going to work.
Just fit normal gears to it like it was designed for. It'll work much better.
Would you try to remove the gearbox from a bus and replace it with a derailier system?
Actually you probarbly would wouldn't you. 😆
It does work though.
The aluminium drop outs were originally intended as a sort of Proof of Concept idea, just so I could ride the bike solo to check it all worked.
We then rode it two up and it seemed to be working OK, so I was tempted to keep them as the finished item.
After today though, I think it would be best to make them in steel.
It's definitely time to make some steel ones.
That slot was parallel when I cut it. The torque reaction of the Rohloff hub has opened it up.
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I think this is good bodge and I fully support it. I look forward to further progress.
Last Thursday, this was a bit of bus engine.
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By Friday, it looked like this.
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By Saturday, it was a bit tidier and I'd ground one of the bolts down so that it would fit flush.
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Two steel dropouts in place.
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That M5 bolt at the top is all that stops the right hand dropout rotating around it's mounting bolt under chain tension.
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We went for a ride yesterday and found that the dropout tries to rotate and ends up taking up all the clearance in the bolt holes so that the wheel pulls slightly to the left.
I'll be using anga's idea of a small block welded to the dropout, butted up against the frame, to stop it moving.
A single bolt will never stop anything from rotating. I've been reminded of that many times!
You don't need to weld a block, just put a small (M4, M5?) cap head screw in the right place to do the same thing. May be two to stop it rotating the other way. Drill the holes slightly big so you can butt the head up against the drop out.
It's not quite a single bolt holding it all.
The big countersunk M10 bolt is taking the vertical load. It was only that small M5 bolt that was preventing the chain tension overcoming the clamping force of the M10 bolt and turning the drop out.
Neither bolt is an interference fit, so all that was happening was that all the slack was being taken up in one direction. Although, if the bolt ever sheared, it would have moved a lot further.
I've modified it now.
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We've been for a 15km ride and nothings moved, so I think that's the solution.
I did think about just using a bolt as a stop as that would have saved a trip in to work on a Sunday to use the welder, but it's bearing against an aluminium frame, so I wanted to spread the load.