Best way to enlarge hubmotor spoke holes? How tight a fit?

[Offroader]

This is on my full suspension ebike with something like 10" of rear travel.

I didn't know spokes helped absorb shocks. I doubt it my case it will make much of a difference as I use a very large 3" tire run at 15PSI. The tire alone absorb a huge amount of shock.

I'll keep you updated with the build. I am going to put white out on each nipple and spoke to see if any movement happens in the spokes.

 

[bowlofsalad]

"Perfect uniform tension on each spoke," How do you know? How much tension is on your spokes?

"The other issue is the spoke doesn't wrap around the flange near the elbow as tightly as the thinner spokes. I'm not sure why this mattered and if it matters in my case.

The obvious place for next breakage will most likely be the flange. I am hoping that because of the sharp spoke angles that some force are distributed sideways in the flange and not completely up, so that the spoke doesn't pull through the thin steal above the spoke hole in the flange. "

https://imgur.com/ea1GdZq is the head of the spoke touching the hub? If so, that is very bad. The worst case scenarios involve either the spoke head breaking or the elbow breaking. If you can slide a piece of paper between the spoke head and the flange near where I drew that red mark on your picture, you might be ok on that aspect, but I'd still be concerned about the wiggle room (up and down) of your spokes elbow/head region. You might need some washers under the spoke head.

 

[cal3thousand]

https://imgur.com/ea1GdZq is the head of the spoke touching the hub?

The flanges are normally countersunk to reduce the stress point near the elbow. Not sure if I can see how these sit against the it.

I'm interested to see how this wheel holds up to your riding. Are you going to put it to the standard 'offroader' test?

 

[Offroader]

Yes the spoke head may be touching the motor at the very tip of the spoke head. The spoke holes are countersunk and the 9 gauge spokes start to enlarge towards the head and this area is in contact with the countersunk area on the flange. The spoke head does not sit completely flush in the hole like a smaller spoke because the heads are so big.

These spokes are so strong and massive that I don't think the spoke would break because the tip of the head touches the flange, I would think it would just conform?

So I took the bike out today for a 27 mile run of almost complete offroading. My purpose was to vibrate those spokes loose and take the wheel out of true. Basically to test how good my wheel build was. I marked each nipple and spoke with white out as shown in the picture. I beat my bike as hard as I could on some pretty tough trails. I made sure to ram that rear tire hard while hopping logs, roots and anything I could.

I couldn't believe that the spokes didn't move at all. I was constantly checking it during my ride and could not believe that I had zero movement in the spokes.

You have to understand this is my 5th wheel build using these prowheel rims and I had constant loose spokes. Especially the rides after my wheel build. Each ride I actually turned my bike around and checked spoke tension. I was checking spoke tension and loose spokes multiple times per ride sometimes, it was driving me crazy.

It gets even better, I had the wheel trued to .01 inches or .25 mm after my build. When I got home I wondered how much my wheel came out of true. I figured it had to come out of true a little bit as all new wheel builds supposedly do? I could not believe that it was still within .01 or .25mm, it didn't move at all.

This wheel was so true that when I first starting riding my bike I thought my bike was power/watt limited at first as it felt slow. Basically the ride was so smooth that my bike felt slower, but my speed was still 40MPH as always. I felt like I was doing 30MPH when doing 40MPH. My other rims were bent and so out of true with bad wheel hops that they made the ride that harsh. Another interesting thing I thought is that when the road was very smooth it felt like I was floating on air as it was so smooth. This shows how important it is to have a very true wheel.

The other great thing was that it was such a relief to not worry about my wheel and spokes. I noticed that my confidence and riding skills have increased because I know my wheel can finally take the hits and won't pop (that's what it sounds like when I break 5+ spokes with one hard hit, which I unfortunately heard too often) or loosen up. I can concentrate more on the trails and not on if my wheel is going to fall apart or how loose the spokes are getting with the hits I am doing. I just bash my bike down the hardest trails.

I didn't climb stairs yet with the wheel. I figured I would work up to that as stairs seem to be very hard on my wheel builds. It's the climbing the stairs and not the riding down that is hard on the rear wheel. Part of me doesn't want to ruin my perfectly trued wheel with stairs, but I can't resist and was one of the reasons I built my bike. I think the rim should be able to take it now without any issues.

 

[Offroader]

I wanted to add that it was obvious I didn't use enough tension on my other builds because the spokes were unloosening. Would more tension have stopped the spokes breaking on hard hits I don't know for sure. I thought I had those spokes reasonably tight.

So I am not going to say at this point that 9/10 gauge are better than 11/12 gauge or even 12 gauge when I didn't have my wheel tensioned properly.

Will I personally use smaller spokes again? absolutely not.

 

[bowlofsalad]

I wanted to add that it was obvious I didn't use enough tension on my other builds because the spokes were unloosening. Would more tension have stopped the spokes breaking on hard hits I don't know for sure. I thought I had those spokes reasonably tight.

So I am not going to say at this point that 9/10 gauge are better than 11/12 gauge or even 12 gauge when I didn't have my wheel tensioned properly.

Will I personally use smaller spokes again? absolutely not.

It's kind of hard to imagine what is going on with a spoke while in a wheel. I kind of think of it like a guitar string or a trampoline spring. For these things to work, they have to be under the right amount of tension and stay that way, just like a spoke.

Another thing to consider are the purpose things were made for. I wouldn't use guitar strings on a trampoline or trampoline springs on a guitar. Just like I probably wouldn't use triple butted 13/15/14ga spokes on a hill jumping dirtbike nor would I use the tree trunks you call spokes on a electric bicycle. If you were going to make an electrified bicycle, especially in the case for transportation as many do on this forum, the common opinion around here of using thinner spokes would probably be a safe bet.

I couldn't tell you if you had enough tension on your previous wheels, but the only difference which makes no difference is no difference.

If I was making a wheel where a lot of jumping was involved, I'd probably not use a hub motor, I'd probably use a chain drive of some sort. You might consider looking into the idea of using some really light loctite (also called thread locker) in this wheel build, loctite 222 is something I've seen recommended on forums and in wheel building books for spokes. I am no wheel building expert, but I imagine downhill biking, dirtbikes or very fast ebikes are all great candidates for some sort of thread locker.

Personally, I don't really get the appeal of massive hub motors. For a while I thought that they were more efficient and that the higher thermal capacity was always better. These massive hub motors have huge rotational weights, and don't make great wheel hubs. Using a separate motor with a chain drive isn't just going to be cheaper, it opens up so many options. There is plenty opinion around about really massive thermal capacity and ways to improve these capacities (oil, vents). You might just be able to find a water cooled electric motor, and pair it up with big radiator for some insane thermal capacities. Maybe make the cromotor mammoth look like a wind up toy.

I couldn't tell you for certain how the spoke head touching the hub is going to interact, I guess in your case, time will tell. Maybe the spoke head will just gouge into the hub, maybe the spoke elbow will break, maybe the head will pop off like a dandelion, or maybe a thousand beautiful people will dry hump your wonderful dirtbike to celebrate it's glory, who knows. I am hoping there will be humping though.

 

[Offroader]

Just to give an update. I put around 200 miles on the wheel. Lots of hard off-roading. I also started to do drops again with my bike, like launch over a small staircase, or maybe launch from the top of 3 feet small hills. I also rode down plenty of steps. Today I started to ride up my first stairs.

The Tire was trued to .25mm and seemed to have lasted for two rides or around 50 miles. I then checked it again at around 100 miles and it is now within .5mm.

None of the spokes moved at all, as all have been marked. I am not sure why it came out of true between 50 and 100 miles by .25mm. I wonder why it didn't come out of true during the first 50 miles.

I checked it today and it is still trued to .5mm, even after riding up some stairs.

I am going to start my stair climbing and more urban assault riding again and will be checking every few rides to see if climbing stairs knocks the tire out of true.

So far I am very happy with the build. I haven't adjusted or touched any of the spokes since I built the wheel and there was zero nipple movement. This is such a relief not to have to constantly check spoke tension each ride. I honestly never thought this was possible on a hub motor wheel. I don't carry my spoke wrench with me anymore. I used to even check and tighten my spokes sometimes twice per ride. Words can't describe the nightmare I had with my other wheel builds.

My offroading skills have also improved since I don't constantly think about my rear wheel anymore. I don't worry about it failing or coming loose, now I just plow over everything without concern.

It took me 5 complete wheel builds (and two badly damaged rims) to finally get it right, this doesn't count constant spoke repair during each build.

When I take a 12 gauge spoke in my hand, I wonder why I ever used such a tiny spoke. It's all physics, a few spoke elbows have to take the high forces when I rammed things while also giving full throttle, those tiny 12 gauge elbows just aren't strong enough too withstand those forces.

Plus those thick shinny spokes just look bad ass. I look at the spokes sometimes and just admire them.

This is the weight difference.

9/10 gauge spokes and nipples are around 15.5oz for 36.

12 guage spokes and nipples are around 10 oz for 36.

The extra weight of the spokes is around 5 or 6 oz.

 

[arkmundi]

Glad it worked out for you.

 

[Tench]

It might be worth retensioning the wheel now you have "settled it down" with some use. This is always a good idea on any wheel build after a good shake down and can only be good for the integrity and longevity on the wheel.

 

[skeetab5780]

It almost seems like it was the spoke angle of your original rims that was causing the breaking issue, it looks like the new black rim has much better angle causing less stress. But we will never know now with those diesel huge spokes in their place.

 

[Offroader]

I don't know if that was the case because I had a holmes MMP rim for the build before this and that had straight spoke angles for the 12 gauge.

I think why I was really breaking them easily was climbing things too fast that had a curb or stair at the bottom. I notice that if I come fast at stairs the rear wheel really hits hard while the front of the bike is lifted. It may be because of leverage or something that has to do with lifting the front of the bike up while hitting the curb or step.

Since I upgraded to 17" wheel, The torque is so much greater that I can simply just drive right up to the steps, stop and slowly give throttle and climb them slowly. No need to come at them with speed to get the momentum.

I can't get myself to really hit those steps with speed anymore because I don't want to possibly damage something, like the rim or cromotor flange. I doubt I would break anything, but don't want to chance it.

This is why I think most people will get away with 12 gauge spokes on the rear because they just don't subject the bike to these hard hits and always go slow over curbs. But I think that eventually they will hit a huge pot hole or something and the rim will fail.

I have to build another 17" wheel for another cromotor I have and I can't decide if I want to go with 9/10 gauge again or straight 10 gauge. The 10 gauge may require almost no drilling to get the spokes in and I am thinking that straight 10 will be strong enough and are cheaper and easer to use. The spoke heads may also be smaller and fit better. Since I'm not doing things like driving at stairs super fast, or over curbs at 20MPH, should I even bother with the 9/10 gauge.

However, drilling for the 9/10 gauge isn't that much and does make for a stronger spoke. The added weight must be close to minimal. I also had no problem breaking 11/12 gauge, so the 11 gauge was not strong enough, 10 gauge may not be either.

I just don't know, I keep changing my mind. I do know that if I break at least a few spokes in a hard hit, which I have done over 10 times with the smaller spokes the $100 rim is now bent and toast as it will not be round anymore. Are using 9/10 gauge worth it just for that reason alone?

What do you think, use 10 gauge straight as they are plenty strong and require no drilling of the cromotor flange, or just get the 9/10 gauge as its cheap insurance against ever breaking a spoke again?

 

[johnrobholmes]

I would use straight 10g because of how thin the flange is.


It sounds like your problems could have been tension related. Too low of tension and the spokes will break at the heads from constant flexing and stress fracturing. When the spokes are not strong enough they typically break at the thread end from stress risers of the thread. But your riding into stairs at speed is a wild card that could have flexed the rims enough that no short spoke would keep tension. There just isn't much length and stretch to work with.

 

[cal3thousand]

If you wheel is really stronger with 9/10 Ga, you'll put it through that same test without any real worry :wink:

Worry means you're not exactly sure that it is better, just hoping.

 

[Offroader]

If you wheel is really stronger with 9/10 Ga, you'll put it through that same test without any real worry :wink:

Worry means you're not exactly sure that it is better, just hoping.

I know, but I am not so worried about breaking spokes as breaking the flange or motor. The other issue is I'm running 14-15PSI and worry a bit about actually bending the rim. I'm not sure how much the tire will compress at that low PSI.

The other issue is I had rubbing in my cromotor which I am not sure if I bent the side covers or if it was because of the magnets coming unglued. When I reglue the magnets I will have to find out if I actually bent those side covers.

I am so happy to finally have a maintenance free wheel now that also allows me to beat it to death and stays basically perfectly true. It hasn't had one nipple unscrew/loosen yet.

I don't want to ruin a good thing. But 9 gauge elbows are so massive, I can't see breaking before actually pulling through the flange. On my other cromotor one flange hole I can feel slightly where the spoke pushed the steel up. It is a very slight bump if you run your finger on top of the flange over the spoke hole.

Like John Holmes was saying, the flange is weak and thin. I think 9 gauge may still be fine as it only needs to be very slightly enlarged, probably only .1mm in the thin area, which should not make much of a difference. But requires a lot of work to get the spokes in the flange because it is such a tight fit.

 

[Chalo]

thnks for the pics - looks & sounds like a nice build. let us know how she rolls.

If that wheel rolls like it looks, that would be like a Model T.

I wonder why so many folks here want to remake their rides into the retarded stepchildren of cars, when bicycles are the fathers of airplanes.

 

[Offroader]

Here is a video of me practicing riding over logs. I'll do this like over 10 times in a row for practice.

When the front is lifted up like that all the weight (130lbs bike) gets slammed real hard when the rear tire makes contact. You can see that it hits so hard the front slams down.

Still can't make a single nipple move from initial build as the white out is still in its original position and I beat this bike endlessly. Simply amazing, and shows that proper spokes and tension is all you need.

[youtube]fKmLpTQoGFY[/youtube]