DasDouble wrote: ↑
Mar 23, 2018 8:26 am
This is what he replyed.
"Although in principal it looks like it would work on a steel frame but it is a custom alloy frame and is not designed to bend plus is heavily braced around the chain stays to account for a wheel with a motor of a given high wattage.
the frame was built with 135mm O.L.D in mind...
Although that QS motor has issues of its own and may not reasonably be used with 135mm OLD dropouts, the bigger problem is that the swingarm was sized to 135mm in the first place by/for someone who doesn't seem to have ever mounted a motor.
Putting a steel axle in an aluminum frame typically is going to require at least a washer in each side to distribute the force when tightening down the axle nuts to avoid sinking the shoulder into the aluminum. This may not be necessary for motors with substantial axle shoulders to the threaded part, but it's a common problem. Another common issue is the need to put a spacer on the freewheel side to clearance the freewheel/chain from the dropout. Again, this isn't always necessary, but it's not uncommon. To build up a custom frame for exactly 135mm really doesn't make any sense since the odds are that even with a 'proper' motor, the chain stays will need to be sprung a bit to accommodate these commonly required extra bits and pieces.
This shot of the tiny axle shoulders on the QS motor shows the need for some help be usable in an alloy frame. Washers may work, but axle spacers with a shaped hole pick up more of the shoulder surface.
If we look at the Xlyte motor, again there is a tiny axle shoulder and perhaps the need for a spacer for the freewheel (as shown on the axle). That spacer is certainly not part of the axle "135mm" specification.
Anyhow, the point being, there is a bit of responsibility for the situation to spread around here and the swingarm guy had an easy option to address common mounting issues with a bit of extra spread but has instead adhered to the industry 135mm standard that creates at least minor issues for many if not most motor installations. A little extra unneeded spread can be easily filled with a washer or two.
To try to fit that QS motor, I would go to a standard 5mm spacer and relieve the section near the flat side of the axle - this is 90 degrees away from a standard "C-washer" which would not work here. Maybe something like this with the notched side against the cable and the remaining solid bit against the dropout. If the owner won't accept any chainstay spring at all, he may be in a bit of pickle regardless of the chosen motor unless he goes to a motor without the QS cable issue and clamping TAs to eliminate the need for axle nuts and an inside washer on the brake side.
This is an awkward situation - hope your client will be a little flexible with working this out since the whole swingarm thing is a bit of a mistep (IMO).