Drilling a hole in the axle?

[Aneta]

I want to drill a hole in the axle on the other side of where phase and Hall wires enter the motor - for redundancy, I want to pass a second set of wires from the other side. I can't do it myself, I need to find a shop in the US that will do it. Any hints on how to find such a shop? I'm not familiar with all these custom manufacturing/metalwork shops oftentimes located in some sketchy industrial areas and don't know how to even find them. And how much one can expect to pay for this? I hope it's not like 200 dollars, I'm willing to pay no more than 40 bucks.

[Rehab1]

Unfortunately there is not enough room to pull a secondary set of motor and hall sensor wires through the side of the axle even with an additional conduit drilled through the other end. Plus the axles are hardened so the machining process may very well compromise the integrity of the entire structure. 

 

Edited January 4, 2020 by Rehab1

[Aneta]

I didn't quite understand that, why there's not enough room at the other end? Isn't it the same diameter on both sides? Drilling a second hole is not new and is sometimes done by e-bike/e-scooter DIYers. Even by regular drill, but not with pretty results as it's hard to make it coaxial without special equipment.

[Rehab1]

Maybe axles have changed. I remember barely having enough room to pull the 8 wires through the side opening of my old ACM’s axle. 

 

Suppose you could enlarge or create another wiring entrance to feed the secondary wires leading to your newly drilled axle shaft. 

I would just be worried that drilling a larger hole would attenuate the construct and eventually fracture the assembly. Good luck.

Edited January 5, 2020 by Rehab1

[The Fat Unicyclist]

Assuming that this could be done, what would the objective be?

Are you wanting a second set of wires connecting to the same hall effect sensors and electromagnets? And if you are what would be on the other end of those wires?

[Aneta]

No, I'm not talking about exiting 16 wires into the motor through the same hole. I must be missing something. I'm talking about fully symmetrical axle, with both entrance and exit holes being symmetrically done on both sides of the stator, with 8 wires through each hole, of the same diameter. I'm thoroughly puzzled now. I guess I need to open up my motor and see for myself if it's possible.

[Aneta]

Both sets of wires (5 Hall and 3 phase, on each side) will be parallel and joined (respectively, of course) just before the controller. Controller "sees" no difference, but there's redundancy in wires (and 4x less heat on each phase wire due to current being 2x less) and connectors (two MT60 phase connectors and two 5-pin Hall connectors).

Edited January 5, 2020 by Aneta

[mrelwood]

To drill a hole in an axle that’s supposed to carry us after months and years of large stress from riding down curbs and hitting bumps, mind you an axle that is known to sometimes crack on it’s own, is just plain bad idea. Especially since it’s made of hardened steel, which drilling would weaken further than the existing hollow axle on the other side already is.

To do this to ”increase safety” by fixing an issue that is already extremely rare... Is a very bad idea. I haven’t read of a single faceplant or other issue that a set of redundant hall sensor wires would’ve prevented. But I have read of several broken axles, the most recent from a very peacefully riding local guy.

Aneta, don’t do it.

 

Edit: So, motor phase wires as well. Which means that the drilled hole must be very large.

Whenever the phase wires fry, they seem to always do it outside of the axle. The ones I fried on my MSX were no exception, the wires were intact for the section that used to be inside the axle.

There’s just not science or logic that would support executing this idea, no matter how sound the intention.

Edited January 5, 2020 by mrelwood

[Aneta]

But the hollow side of the axle is not bending, why would either side bend if an exact same diameter hole was made on the other side? The bending stress is not transmitted from one side to the other, it's concentrated between stator and pedal hanger's edge.

[Aneta]

From my experience with e-bikes and e-scooters, even 12AWG wires for both battery and phases become very hot even at currents of 30A battery and 70A phase. For hoverwheels, battery currents of 50A and phase >100A are not unheard of, on steep slopes or hard acceleration from standstill. In my GT16 phase and battery wires look no thicker than 14AWG, and phase wires are pressed against each other tight in the axle hole and there's no air circulation, so the temperatures there could be extreme. Reducing the heat by 4x factor would eliminate all concerns.

Edited January 5, 2020 by Aneta

[The Fat Unicyclist]

FWIW... The KS-18L/XL has the wires split across both ends of the axle. The KS-16X may as well - I can't recall (I haven't torn down enough of them)...

For the 18L/XL though the wires are split with the hall sensors on one side and the power cables on the other (not duplicated). The challenge with running all wires in parallel would be the larger hole required, reducing the strength the axle was designed to have.

I also wonder if there would be any impact of two sets of motor wires in parallel if they were different lengths... Electrical engineers, please jump in here... If the wires were different lengths would that confuse the timing (for either the hall effect sensors or the motor)?

[Gaz Bon]

38 minutes ago, The Fat Unicyclist said:

The KS-16X may as well - I can't recall (I haven't torn down enough of them

16x hall wires on one side of axle and motor cables the other

[mrelwood]

2 hours ago, Aneta said:

But the hollow side of the axle is not bending, why would either side bend if an exact same diameter hole was made on the other side? The bending stress is not transmitted from one side to the other, it's concentrated between stator and pedal hanger's edge.

I fail to follow. Surely you agree that the hollow tube of an axle is under a lot of stress, since the rider is standing beyond of the attachment point, trying to constantly bend the axle with one’s full weight. And even more on bumps.

1 hour ago, Aneta said:

From my experience with e-bikes and e-scooters, even 12AWG wires for both battery and phases become very hot

Becoming hot is not an issue, it is normal operation. Teflon and silicone coated wires are rated to withstand temperatures in the range of 200-300˚C. If there is a huge steel element surrounding them and cooling them down, I’m pretty sure it’s next to impossible to get the wires to overheat. The axle is to the wires what a heat sink is for the Mosfets.

1 hour ago, Aneta said:

Reducing the heat by 4x factor would eliminate all concerns.

And what exactly are all the concerns? That the wire shields will melt inside the axle? Have you heard or read that ever happening on an EUC? Why would you worry about that, but not about the axle strength even though there are numerous cases of snapped axles even without weakening the structure by a random steel shop that will have no idea what the exact material even is, or what kind of forces the rider’s weight load will apply to the axle? You’d have to calculate the forces, steel durability, and drilling temperature’s affect on those very precisely for the idea to make any sense. And without even knowing the exact steel compound used, how would you do that?

 

[Aneta]

The reason I'm so concerned about overheating and redundancy is because I like to conquer the mountains in the American West, and did a lot of rides on my DIY 3000W 2WD e-scooter last summer, with elevation gains of 1500-2200m at a time, and with total elevation gain for all rides probably like 5 Everests. So I know very well how the components, even distributed between two powerful motors, not one, and air cooled much better than on hoverwheels, heat up to very high temperatures so possibility of charcoaling the windings, melting the solder between phase wires and windings, fusion of phase wires touching each other in the axle, magnets going over the Curie point and losing their magnetism, controller frying, battery overheating and starting a thermal chain reaction are very real. It can easily be +35-40C even at high elevations in the summer in Eastern Sierra in CA, Rockies in CO, let alone Great Basin desert mountains in Nevada, Arizona, Utah, where +45C is not unheard of. I did have a motor failure on my smaller scooter where the solder inside motor melted. Such a failure would be catastrophic while riding a hoverwheel.

So far, I've done several mountain rides on my Rockwheel, with the highest elevation gain of about 1100m, which is limited by the size of GT16's battery (1036Wh). But it was done in the Fall when it was already freezing at altitudes of 2500-3000m, so it helped. But I was still concerned, since I don't have any means to know the temperatures of wires and solder joints. The controller was reaching up to 70C. What would happen in the summer, at air temperature +35C?

I guess it's very different in Finland, it's much flatter and cooler? That would explain the lack of concerns about overheating.

[mrelwood]

1 hour ago, Aneta said:

I guess it's very different in Finland, it's much flatter and cooler? That would explain the lack of concerns about overheating.

Mind you, I have fried my MSX, so I know first hand what happens when the motor phase wires melt. Several other people have fried their MSXs too (although they seem to have since changed the design in a way that is likely more resilient).

But I’m not referring to my own concerns here, but reflecting the issues I have read about here during these three years. And most notably the ones I haven’t seen mentioned. I would think you’d have searched and read about all possible GT16 issues and failure points by now. I’m pretty sure they are even of more value than your personal experience with scooters, as the failure points vary so much already between different EUC models. And while heat is heat, the wheels differ in how they generate heat, and which part is most likely to fail first. The 18XL for example, my guess is that it can’t be overheated catastrophically since the phase currents are monitored and controlled, and it will warn the rider if necessary. Polar opposite to the MSX, which is seemingly all fine and dandy until it literally melts all over.

Have you read about instances where the GT16 phase wires have melted? If so, where exactly did they melt, and how was the wheel being used to achieve that?

But to drill a hole through the axle and then go stress the wheel on the mountains? That’s some different level of ”brave”, that I don’t even call ”brave” anymore. The heat from the drilling will change the steel’s properties, as it provides a non-controlled tempering process. So it might remove some or all the strengthening effects that were achieved when the steel was originally hardened for it’s planned purpose.

If I were you I’d rig up temperature sensors all over the wheel’s insides, especially the cables, and if nothing else, a simple row of LCD displays taped on top of the wheel. And more importantly, do as many test rides in similiar circumstances as possible, since there will surely be several aspects you (and us) fail to think of beforehand.

[Aneta]

The main question remains: how to find a shop capable of drilling axles with high precision, in the West US?

[Rehab1]

15 hours ago, mrelwood said:

If I were you I’d rig up temperature sensors all over the wheel’s insides, especially the cables, 

I used a digital temperature data logger on my ACM a few years back when burnt motor wires were a common occurrence. 

 

4 hours ago, Aneta said:

The main question remains: how to find a shop capable of drilling axles with high precision, in the West US?

There is a plethora of tool and die machine shops in your state. You’ll just need to call around.

In order to precisely drill a shaft into the other end of the axle it will first need to be extracted from the motor’s hub.  A milling lathe will probably be used to accomplish the task. Once drilled the axle will need to be heat treated again. The entire process will be costly. 

[Marty Backe]

On 1/4/2020 at 12:33 PM, Aneta said:

I want to drill a hole in the axle on the other side of where phase and Hall wires enter the motor - for redundancy, I want to pass a second set of wires from the other side. I can't do it myself, I need to find a shop in the US that will do it. Any hints on how to find such a shop? I'm not familiar with all these custom manufacturing/metalwork shops oftentimes located in some sketchy industrial areas and don't know how to even find them. And how much one can expect to pay for this? I hope it's not like 200 dollars, I'm willing to pay no more than 40 bucks.

$40??? I don't think you have any understanding of work, particularly quality work that would be required to do what you're seeking. You value skilled labor very cheaply 

If your only alternative is to pay someone to do this work, I would anticipate hundreds of dollars.

[Aneta]

Hundreds of dollars?! I'm not talking about dropping off my hoverwheel at the shop and saying "I want it tomorrow with the additional hole, fully wired up and ready to go", and they spend a full workday figuring out what the hell is this and how to take this thing apart and not damage anything. I bring to them the fully prepped stator, or even just the axle if I figure out how to extract it myself, with everything thoroughly protected and ready to be mounted in a vise of a plunge press drill or lathe, they just need to center is precisely which I'm sure they already have means to do, otherwise all their works would look amateur. Drill a 40-50mm long hole - how long can it take? And for that simple drilling for several minutes, they'll charge me hundreds of dollars?!

Edited January 6, 2020 by Aneta

[Aneta]

 

 

 

Edited January 6, 2020 by Aneta

[Marty Backe]

51 minutes ago, Aneta said:

Hundreds of dollars?! I'm not talking about dropping off my hoverwheel at the shop and saying "I want it tomorrow with the additional hole, fully wired up and ready to go", and they spend a full workday figuring out what the hell is this and how to take this thing apart and not damage anything. I bring to them the fully prepped stator, or even just the axle if I figure out how to extract it myself, with everything thoroughly protected and ready to be mounted in a vise of a plunge press drill or lathe, they just need to center is precisely which I'm sure they already have means to do, otherwise all their works would look amateur. Drill a 40-50mm long hole - how long can it take? And for that simple drilling for several minutes, they'll charge me hundreds of dollars?!

Like I said, I don't think you appreciate skilled labor and the value of a man's time. In my youth I did machinist's work for some years. That, plus life, has taught me the value of skilled labor. 

When you see your Doctor, does he charge you $20 because he only spent 10-minutes with you? Overhead, the value of his knowledge, etc. Doubtful.

You may be able to find someone who doesn't yet know how to value his time and charge accordingly, but that person probably won't provide the outcome that you'd like.

[Rehab1]

3 hours ago, Marty Backe said:

You may be able to find someone who doesn't yet know how to value his time and charge accordingly, but that person probably won't provide the outcome that you'd like.

Yeah there use to be some guy on the forum that would modify member’s tools for free but he has since retired. 

Edited January 6, 2020 by Rehab1

[RockyTop]

You can’t just drop this on a drill press and drill. They would likely use a lathe to bore the hole. Also as @Rehab1 Said the axle is very likely hardened steel. (Cheaply and poorly hardened) Drilling would be very difficult using bits that are very expensive. Depending on the hardening process used the steel would then be severely weakened. 

Price: $75 -$200 per hour (two hour minimum?) plus cost of bits used. 

I would take another approach. Instead of drilling through the existing axle I would make a new one from scratch with holes in each end then harden the steel. Machine shops are more used to and set up for making new parts rather than altering and damaging hardened steel. 

If you could wait a week your axle would get tossed in with other projects and flow threw the shop painlessly. 

[Aneta]

You're absolutely right, what was I thinking?! New axle means zero risk to the wheel until the axle is ready. How's the axle extracted/fixed in the stator? Is it just pressed in and is held by friction? Does it require a powerfull press to extract/insert, or can be done at home?

[RockyTop]

From what I have seen they are tack welded, pressed or both. Welds are usually easy to remove. pressed is easier. The 

inMotion axles are easy to remove.