Drilling "jig" to add new spoke holes to hubmotor

[amberwolf]

I found myself with the need to drill new spoke holes for smaller (13/14 butted) spokes, in an MXUS 3K that seems to be pre-drilled for what look more like motorcycle-sized spokes.

A handheld power drill wouldn't work, as I couldn't make a consistent angle, or hold it and the motor properly to get the holes right, and also to not break drillbits. :/

But I have a little HF drillpress, from one of their "big sales", if only I could find a way to hold the motor itself so that it would sit axle parallel to the drill, and flange perpendicular, in a way that lets me just rotate the hub for each new hole in one flange, then flip the mtoor over to drill the other flange holes.

The two obvious ways are to use either a vise or to build a "dropout" to bolt the motor to via the axle nuts, that then bolts or clamps to the base of the drillpress.

The latter would take a fair bit of work, but the vise method should be easy, right? I tried a few variations of the vise method using a small vise, but I couldn't get it to fit in a relationship with the press that would allow lowering of the bit into the flange at a perfect (or even close) perpendicular angle, except from positions that would not reach the flange at all, or that could not withdraw the bit from the flange at all.

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I dug out my larger vise (which needed repair, see here: https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1260615#p1260615
) and that just worked out fine. I secured the vise to a board, then clamped the board to the cart the press is on, with the press's base under the board.



Clamped the motor in the vise, using the torque washers on that end for stability and to help it stay in place as I turn it around for drilling. Then I tapped the board around until the drill bit lined up with the spot on the flange I want the holes to end up, and tightened teh clamps holding the board to the cart.



I setup the press's "shelf" to support the opposite flange/side of the motor, so when drilling down thru the flange, it doesn't move away and change the angle of the hole (or break the bit).





I've only had time to drill one hole so far, but it worked as planned for that one. Will see tomorrow how well it works for the rest of them.


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[docw009]

Nice set up.

I have a similar drill. At least 16 years, it's been drilling.

 

[Chalo]

I've used rotary tables and CNC to do that job before, including making custom drill bushing plates that can be used outside a machine shop setting.

But for hub motors and the required level of precision here, I'd probably use calipers to scribe the center points, punch them, then drill with a drill press or by hand. If you get within a millimeter, no problem.

Just last night I relaced a Rohloff hub that I custom drilled for 48 spoke lacing back at the turn of the millennium. This time, with all the better rim options in 32 hole, I reverted to the original intended lacing pattern.

 

[Baron]

what are the advantages to smaller spokes? more flex, less chance to break?

I have an edge 1500w with "motorcycle size" spokes in a 17" rim and I'm now realizing it might be a disadvantage

 

[amberwolf]

If you're using a motorcycle rim with them, there's no problem using motorcycle spokes, too (as long as the motor's flange can also handle the tension).

It's when you use a bicycle rim that thinner spokes are necessary to allow full tensioning of htem without damaging the rim (either immediately or long-term). If you don't tension them fully, to avoid damaging the rim, then you end up with spokes that either get loose and come apart, a wheel that wont' stay true, or spokes that keep breaking (at the elbow).


Another case that thinner spokes can help with is very short spokes, like mine with the radial lacing in the 20" rim and the giant hubmotor in there. I think the spokes I'm using are 74mm on the old 9C wheel, and 77mm on the old x5304 wheel (am hoping the 74mm are long enough to do the MXUS but probably not--I will probably have to get new 77s for it).

I'm using double-butted Sapim spokes (from Grin Tech) so the elbows are thicker (13) and the rest of the spoke is thinner so it can stretch (14g) under loads, and not just loose tension and work loose or break.



I finished up the hole-drilling, and only really screwed up one hole (the last one); I dont' knwo what exactly happened but hte bit tip shattered in the hole before it went thru. Perhaps ther was an inclusion of something harder inside the casting? Dunno, whatever it was I had to pick the pieces of bit out of the hole before I could use a crappy old drillbit to then work the rest of the hole thru, and it's definitely not a normal hole--it's got part of an extra offset hole in it now due to problems with the crappy bit.

Hopefully I won't have troulbe with that spoke because of it, but I wont' know till later on once the wheel is built. If there is likely to be troulbe, I could weld the hole shut and redrill it, but I don't know what effect that will have on the steel so I'd rather leave it alone until I run into problems (if I do).


After the hoels were drilled, I then took my Unibit in the handheld powerdrill, and beveled the edges of the holes a tiny bit to help with seating, and to remove all the flash from the drilling. Will have pics of everything a bit later; dogs are laying on my legs right nows o can't reach the camera to get the card to read into the computer.