Basic possibly stupid question about dropout hangers

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tolkaNo
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Basic possibly stupid question about dropout hangers

Post by tolkaNo » Dec 31, 2017 9:23 pm

Hello i was wondering something

Say you have a dh bike like an older giant glory that can use replacement dropout/derailleur hangers such as this: https://www.sjscycles.co.uk/gear-spares ... a/?geoc=AU

Is it then possible to be able to use a regular axle hub motor on the frame? I know the left side of the frame will still be a hole instead of a slotted dropout so would you be able to thread that in with the axle from the hub motor?

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Re: Basic possibly stupid question about dropout hangers

Post by amberwolf » Dec 31, 2017 10:25 pm

YOu'd want to make torque plates or clamping dropouts that bolt to or clamp to the frame.

See the Torque Arm Picture Thread for a few ideas, or search on
torque plate*

There's at least one thread in the for sale section for versions of them, I think by Miguerillart.

You can also look at the build threads for the various frames like that, wherever they've used their frame name in the thread title or first post to make it easy to search.

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Re: Basic possibly stupid question about dropout hangers

Post by tolkaNo » Jan 01, 2018 3:13 am

amberwolf wrote:
Dec 31, 2017 10:25 pm
YOu'd want to make torque plates or clamping dropouts that bolt to or clamp to the frame.

See the Torque Arm Picture Thread for a few ideas, or search on
torque plate*

There's at least one thread in the for sale section for versions of them, I think by Miguerillart.

You can also look at the build threads for the various frames like that, wherever they've used their frame name in the thread title or first post to make it easy to search.
Yeah i know doing that is definitely ideal, but im wondering is the scenario i presented possible?

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Re: Basic possibly stupid question about dropout hangers

Post by amberwolf » Jan 01, 2018 3:29 am

If the DH bike is a 20mm thru axle type, then your hubmotor axle, which is probably anything from 12mm to 15mm, will just be floating in the hole, unsupported.

So every bump, lean, acceleration, and regen braking you do will bend and twist the axle end that is actually mounted into the slotted dropout.

At some point, sooner or later, you'll get this:
Image
at the stress riser where the axle becomes flat past the shoulder.


Mine was from a different cause, with less stress on that axle than what you're talking about doing, but it still broke. It's happened to others for reasons similar to the stresses you'd be putting on it.

It's not really too hard to make a torque plate to solve the problem, so I dont' know why you wouldn't want to, unless you have a really small low-torque motor. (though even that can still break the axle from the bumps and leaning flexure).

If you don't have power tools you can hacksaw a thick (5mm+) piece of steel so it's Y-shaped in a way that lets you use U-bolts to clamp it to your chainstay and seatstay if that's how your bike is shaped (or a single bar if you only have chainstays), . Then on the rear-pointing part, you can hacksaw a V into it and then file that V out into a rectangle that fits your axle flats, then file the inside end of that round to fit the rounded part of the axle, so it's all snug. See the Torque Arm Picture thread and others for more stuff like that.

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Re: Basic possibly stupid question about dropout hangers

Post by tolkaNo » Jan 01, 2018 5:27 am

amberwolf wrote:
Jan 01, 2018 3:29 am
If the DH bike is a 20mm thru axle type, then your hubmotor axle, which is probably anything from 12mm to 15mm, will just be floating in the hole, unsupported.

So every bump, lean, acceleration, and regen braking you do will bend and twist the axle end that is actually mounted into the slotted dropout.

At some point, sooner or later, you'll get this:
Image
at the stress riser where the axle becomes flat past the shoulder.


Mine was from a different cause, with less stress on that axle than what you're talking about doing, but it still broke. It's happened to others for reasons similar to the stresses you'd be putting on it.

It's not really too hard to make a torque plate to solve the problem, so I dont' know why you wouldn't want to, unless you have a really small low-torque motor. (though even that can still break the axle from the bumps and leaning flexure).

If you don't have power tools you can hacksaw a thick (5mm+) piece of steel so it's Y-shaped in a way that lets you use U-bolts to clamp it to your chainstay and seatstay if that's how your bike is shaped (or a single bar if you only have chainstays), . Then on the rear-pointing part, you can hacksaw a V into it and then file that V out into a rectangle that fits your axle flats, then file the inside end of that round to fit the rounded part of the axle, so it's all snug. See the Torque Arm Picture thread and others for more stuff like that.
Alot of them have rear 12mm through axle no? Meaning the hub axle should still be able to thread on that side, Then on the right side with the dropout adapter you just push that side in like normal?

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Re: Basic possibly stupid question about dropout hangers

Post by amberwolf » Jan 01, 2018 5:42 am

tolkaNo wrote:
Jan 01, 2018 5:27 am
Alot of them have rear 12mm through axle no? Meaning the hub axle should still be able to thread on that side, Then on the right side with the dropout adapter you just push that side in like normal?
If it's a 12mm axle, and a 12mm hole, then the axle will at least be supported and centered, so it won't have the flexing problem at the other end from the bumps and leaning.

But it will still have the twisting forces from acceleration and regen braking (if you use that) countered at only one end. That's where at least a torque arm would help.

If it is a 14 or 15mm axle, it won't fit in the 12mm hole, and the frame will have to be modified, filing material from it (or drilling it), which may weaken that side, depending on how it's made. That's also where a torque plate would help (or at least a torque arm).

If it is a 20mm hole, and a smaller axle, it'd have to have something to hold the axle centered in the hole.

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Re: Basic possibly stupid question about dropout hangers

Post by tolkaNo » Jan 01, 2018 6:00 am

amberwolf wrote:
Jan 01, 2018 5:42 am
tolkaNo wrote:
Jan 01, 2018 5:27 am
Alot of them have rear 12mm through axle no? Meaning the hub axle should still be able to thread on that side, Then on the right side with the dropout adapter you just push that side in like normal?
If it's a 12mm axle, and a 12mm hole, then the axle will at least be supported and centered, so it won't have the flexing problem at the other end from the bumps and leaning.

But it will still have the twisting forces from acceleration and regen braking (if you use that) countered at only one end. That's where at least a torque arm would help.

If it is a 14 or 15mm axle, it won't fit in the 12mm hole, and the frame will have to be modified, filing material from it (or drilling it), which may weaken that side, depending on how it's made. That's also where a torque plate would help (or at least a torque arm).

If it is a 20mm hole, and a smaller axle, it'd have to have something to hold the axle centered in the hole.
Yeah.. well not many hub motors have a 14mm or 15mm axle atleast to my knowledge

I'm more just making the thread because it seemed suspiciously easy to bolt on a hub motor to a dh frame in the scenario i described

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Re: Basic possibly stupid question about dropout hangers

Post by amberwolf » Jan 01, 2018 6:50 am

tolkaNo wrote:
Jan 01, 2018 6:00 am
Yeah.. well not many hub motors have a 14mm or 15mm axle atleast to my knowledge
There's a number of them out there; they're not uncommon. At least some versions of the MAC (and probably BMC) geared hubs have 14mm axles. Crystalyte H40xx series, probably the 35xx, etc. I think the Leaf motors are 14.

I know at least three of mine are larger than 12mm (probably more of them). Both of the MXUS 3Ks, and the HSR3548. I think my Fusin "1000w" geared hub is also bigger than 12, and maybe the Ezee (would have to go measure them). Possibly even my old 9C/MXUS generics (28xx types).

Only ones I know for sure that I've got that are 12mm are the old small Fusin geared hubs, and a TongXin roller-geared hub.

A quick search of ES for 14mm axle* finds a number of posts, though I havent' looked thru them to see how many different motors come up
https://endless-sphere.com/forums/searc ... mit=Search

Haven't checked for 15mm.


FWIW, I think there are some DH forks that use 15mm thru axles, not sure about rear dropouts.

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Re: Basic possibly stupid question about dropout hangers

Post by tolkaNo » Jan 01, 2018 7:05 am

amberwolf wrote:
Jan 01, 2018 6:50 am
tolkaNo wrote:
Jan 01, 2018 6:00 am
Yeah.. well not many hub motors have a 14mm or 15mm axle atleast to my knowledge
There's a number of them out there; they're not uncommon. At least some versions of the MAC (and probably BMC) geared hubs have 14mm axles. Crystalyte H40xx series, probably the 35xx, etc. I think the Leaf motors are 14.

I know at least three of mine are larger than 12mm (probably more of them). Both of the MXUS 3Ks, and the HSR3548. I think my Fusin "1000w" geared hub is also bigger than 12, and maybe the Ezee (would have to go measure them). Possibly even my old 9C/MXUS generics (28xx types).

Only ones I know for sure that I've got that are 12mm are the old small Fusin geared hubs, and a TongXin roller-geared hub.

A quick search of ES for 14mm axle* finds a number of posts, though I havent' looked thru them to see how many different motors come up
https://endless-sphere.com/forums/searc ... mit=Search

Haven't checked for 15mm.


FWIW, I think there are some DH forks that use 15mm thru axles, not sure about rear dropouts.
The theory build i had in mind was the giant dh glory frame, which has 12mm rears, and 3000w qs hub motor with 12mm axles

Might end up doing it if its easy as i think

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Re: Basic possibly stupid question about dropout hangers

Post by Patchogue » Jan 01, 2018 10:32 am

Hi TolkaNo,

I'm assuming that you're from the UK and I must admit that I didn't read all the replies, my apologies in advance.

Here's a couple of rigid frames that I think they're the best for hub DD motors, specially when you're in trouble with wider dropouts. If you're not looking for rigid frames, then I'm afraid I can't help you.

Frame #01, Voodoo Wanga, I've just bought one from this guy on ebay and this frame is a double butted alu frame that can work perfectly with any mega dropout size. You can design and machine torque plates to the size you want. The only thing that is annoying with this very affordable frame, it's for 26" wheels. I wouldn't use the original dropouts for hub motors, the fixings are a bit weak, specially with that bolt that holds the track adjustment.

https://www.ebay.co.uk/itm/New-Voodoo-W ... Swak5Zx-V3

Image

The other frame that I really like is the Boardman CX Team 2012 till 2015?, ready for 700cc but "limited" to 137mm dropouts width. This is a 3 butted alu frame with amazing smooth welds. You can find the silver paintwork that is gorgeous or other options. There are some good deals of used bikes on ebay. I like this frame because is sturdier than other bikes and the dropouts have a great shape to fit torque arms or even torque plates. You can use both holes (mud guards and panniers) to fix your plates.

https://www.ebay.co.uk/itm/Boardman-cx- ... SwaSZaRjHA

https://www.ebay.co.uk/itm/Boardman-tea ... SwVF1aO~kz

Image

Cheers!

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Re: Basic possibly stupid question about dropout hangers

Post by wturber » Jan 01, 2018 12:59 pm

tolkaNo wrote:
Jan 01, 2018 7:05 am

The theory build i had in mind was the giant dh glory frame, which has 12mm rears, and 3000w qs hub motor with 12mm axles

Might end up doing it if its easy as i think
I don't know about the frame you are talking about. But I don't think you'll find anybody here who would not urge you to have two robust torque plates or clamps (maybe not arms) if you are going to be using a 3000w hub motor - pretty much regardless of the frame. So if you think the frame dropouts may be less robust than typical, you REALLY need to be thinking about how to reinforce the mounts.
Last edited by wturber on Jan 01, 2018 6:17 pm, edited 1 time in total.
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Re: Basic possibly stupid question about dropout hangers

Post by amberwolf » Jan 01, 2018 3:12 pm

tolkaNo wrote:
Jan 01, 2018 7:05 am

The theory build i had in mind was the giant dh glory frame, which has 12mm rears, and 3000w qs hub motor with 12mm axles
If it's a 3kw motor, and you run it with a controller capable of using it well, it's likely to have a lot of torque.

All that torque will be applied to the extremely small cross section of axle flat that touches the frame. It doesn't apply any of the torque to anything else, so that's a whole bunch of force in a fingernail-sized area (or smaller!) doing it's very best to destroy your bike.

If it only has a 12mm axle, that is weak for a motor that size already, and is going to be under stress just from the torque even when properly installed and clamped down.

If you only clamp down one end of it, then that end will be under twice as much stress as it was designed to take, and that much more likely to break.


If the axle itself doesnt' break, then that leaves the doubled stress on the torque plate it's in, and the mountings of the plate to the frame.

If it's not in a torque plate, then it leaves the double stress on the torque arm, whcih is usually thinner than the plate would be, and more likely to deform or cut into the axle and allow it to spin in the frame, damaging the dropouts.

If it's not in a torque plate or torque arm, then the double stress is all on the dropout/frame, which was not designed to handle that at all, and what happens to it depends on how it's made, but it's hardly ever pretty or fun.


I don't know why people sometimes don't want to listen to the voices of experience, even when shown what can happen, until after their own stuff breaks and they crash and get hurt, but it's a continuing thing around here. :/

Up to you how you build your bike, but you can't say we didn't warn you and try to prevent it, when either the axle, the frame, the dropouts break, or the axle spins and rips apart your wires and blows up the controller and/or the motor halls. :(


It's quite possible that nothing bad will ever happen.

But I wouldn't put my faith in that, after the stuff I've seen on other's bikes and my own.

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