GO Swissdrive Axle Reams 11 mm Torque Arm

[BretCahill]

These bikes were assembled in Belgium with an 11 mm torque arm. (See photo of broken torque arm.) At higher assists the slack between axle and torque arm allows a build up of enough angular momentum to ream the torque arm when it engages. The axle then reels up the wires ripping them out of the circuit board. Incredibly the circuit board can withstand multiple 600 Newton "events." The hardest part of the repair is desoldering the high temperature solder. For some reason I find restringing and truing the wheel soothing.

I imagine a lot of these otherwise great bikes got dumped simply because no one checked the torque arm. We paid $1,000 for two GO Swissdrives on Gub frames, Hygia brakes, Ferei lights, etc.

I may eventually want a higher assist. A 10mm open wrench fits the axle perfectly and I may resort to that rig but is there any way to source a 10mm torque arm? A GO Swissdrive owner in Geneva managed to cajole an email address from the receptionist at Ortlinghaus but that contact info was never posted online. Eventually they sold him a rebuilt motor so GO Swissdrive may still be more or less supported in some limited capacity.

 

[indianajo]

Oh, come on. That torque arm is too short, anyway.
Saw a 4" x 1" piece out of a bed frame or other suitable scrap metal. Bed frame is high carbon steel. Use safety glasses using power tools. Drill two 5/16" holes next to each other. connect the dots with a nicholson round file, then a nicholson triangle file to make the flat edges. Takes about 90 minutes. Requirements, vise, drill motor, drill, files. Less time if you have a rotary file with 1/4" shank, but takes more skill to not oversize the hole.
Clamp the torque arm to the fork with a U made of sheet metal, say sawed out of a box fan frame. Drill several holes for 10-32 screws, or 5 mm if you have those instead. Use elastic stop nuts on the bolts to keep them from coming loose on the road.

 

[BretCahill]

These bikes were assembled in Belgium with an 11 mm torque arm. (See photo of broken torque arm.) At higher assists the slack between axle and torque arm allows a build up of enough angular momentum to ream the torque arm when it engages. The axle then reels up the wires ripping them out of the circuit board. Incredibly the circuit board can withstand multiple 600 Newton "events." The hardest part of the repair is desoldering the high temperature solder. For some reason I find restringing and truing the wheel soothing.

I imagine a lot of these otherwise great bikes got dumped simply because no one checked the torque arm. We paid $1,000 for two GO Swissdrives on Gub frames, Hygia brakes, Ferei lights, etc.

I may eventually want a higher assist. A 10mm open wrench fits the axle perfectly and I may resort to that rig but is there any way to source a 10mm torque arm? A GO Swissdrive owner in Geneva managed to cajole an email address from the receptionist at Ortlinghaus but that contact info was never posted online. Eventually they sold him a rebuilt motor so GO Swissdrive may still be more or less supported in some limited capacity.

Correction: These bikes came as a kit. The consumer just assumes the right stuff got into the right kit. I guess there were a lot kits where the 10mm torque arms didn't fit on the 11mm axles so they figured it out right away.

 

[BretCahill]

Oh, come on. That torque arm is too short, anyway.
Saw a 4" x 1" piece out of a bed frame or other suitable scrap metal. Bed frame is high carbon steel. Use safety glasses using power tools. Drill two 5/16" holes next to each other. connect the dots with a nicholson round file, then a nicholson triangle file to make the flat edges. Takes about 90 minutes. Requirements, vise, drill motor, drill, files. Less time if you have a rotary file with 1/4" shank, but takes more skill to not oversize the hole.
Clamp the torque arm to the fork with a U made of sheet metal, say sawed out of a box fan frame. Drill several holes for 10-32 screws, or 5 mm if you have those instead. Use elastic stop nuts on the bolts to keep them from coming loose on the road.

I'll check to see if there's a bed frame somewhere. Sometimes it's amazingly hard to find something so simple as a 4 mm thick plate. Then pack common drill bit sizes onto the template area and use a small drill press and dremel cut off wheel.

 

[rich c]

That 1mm let the axle spin? I'd take that torque arm to a weld shop and let them TIG a small bead on one or both of the flats. A little filing will be a lot easier than grinding out a new one with a Dremel!

 

[BretCahill]

That 1mm let the axle spin? I'd take that torque arm to a weld shop and let them TIG a small bead on one or both of the flats. A little filing will be a lot easier than grinding out a new one with a Dremel!

It took over 4 hours and I had to measure so often I may have ruined my caliper. Tire puncturing turnings flew all over. It's a snug fit now but I plan to check it in decreasing frequency, 5 km, 50km . . . and just go to a machine shop if it starts to wiggle more than a couple degrees.

The original in the OP photo is a dark grainy material. The small hole is for a bolt which may also act as a shear pin. Any ideas on why they would want a brittle torque arm? Maybe they were just really nervous about the axle wallering out the torque arm. A machine shop might have some of that brittle metal.

The copy of the original (left side of photo below) must be some kind of stainless. It doesn't break but it will twist off.

The metal I used was hacked, and "hacked" is the right term here, from a strap that attached to the motor of a vehicle, probably mild steel. It was about 4.5 mm thick. The flat spots on the axle extend about 4.3 mm.

Monday I'll get a quote from a machine shop.

 

[BretCahill]

The axle was not designed big enough for the torque. If the axle breaks the motor is toast, so after the original axle got baked into their design, the band aid was a 2X sacrificial torque arm. The tiny cylinder that fits into the chain stay acts as a shear pin. That's why the arm is so short; they needed a big shear force on a thin screw. And they also made the arm from some brittle casting.

(Always beware of 2X sacrificial parts. Someone was paranoid about something. Maybe you need to know what that something is.)

Anyway my mild steel arm started to ream loose after a few miles so I started thinking about epoxying it to the axle and just using lower assists. Another engineer independently suggested calling it a day so the only thing protecting the axle now is the shear pin. If I try to take off in #5 up a hill and the shear pin doesn't break, the cold weld will break the axle. I am now training myself to never pedal until I double check the assist. Don't go to #2 until 15 km/hr, #3 at 20, not a problem in flat rural areas where you want longer range anyway. Eventually I'll get a 1 t bigger rear cog.

Theft or vandalism may be a bigger issue anyway. Get security screws for the battery cover and a quick release for the controller.

Mis matched design points happen more often than you may think, i. e., when the Japanese first moved to large engines on motorcycles, they kept the same chains that worked on smaller engines. These errors are probably due to bad management, office politics, etc., as they could be avoided with little more than back of envelope calculations.


Bret Cahill

 

[Defiant]

If you are looking for Go SwissDrive parts, I may be able to help. I have many new spare parts.

 

[BretCahill]

The cold weld seems to be holding up after 800 miles, maybe because I never risk using the 4 or 5 assists. I can out run any tire biter in the valley on +2.

But I worry about the old 2012 controller being unsupported so I'll definitely keep you in mind. Could a later ver. controller be made to work?

Other issues:

BMZ batteries are several times more expensive than other brands. I was considering carefully taking it apart noting the wiring and swapping out cell by cell. If you could find replacement electronics I could build a 2nd battery. I'd need another magnetic plug

The regenerative brake lines were never hooked up and it appears to be running sensorless as only 3 heavy wires enter the motor. Only 3 fine wires connect to the 5 prong controller. Are the 2 remaining lines, both snipped at the wiring harness, for a Hall sensor or for the brakes?

I'm not too sure about the amp meter reading. I can regenerate one "mile" of charge at -1 on flat land but it takes about 3 miles of slogging it out. The average current is 0.4 amps according to the monitor which for a 36v system is about 15 watts, maybe 2% of an elite cyclist's output. I'm good for more than 15 watts even on a vent in the ICU. Is that amp meter missing a decimal place or is regen just really inefficient? The charger is only 85 watts yet it is 3X faster than my effort. It would take 10 hours of pedaling and $2 of potatoes to regenerate 7 cents of electricity -- not cost effective.

What are units for the "CO2 saved"reading? Liters? The manual skips that screen.