Hub Motor on skewer front fork?

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Brockster   1 µW

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Hub Motor on skewer front fork?

Post by Brockster » Apr 26 2022 12:02pm

I have a Specialized Hardrock from around 1995, give or take a few years. I bought a front hub motor from Battery Clearance House :thumb: and actually got it on the front fork. I have two nuts, one for each side. Since this fork had a skewer-style axle on it, can I use the hub motor with it? If yes, how many nuts, washers etc. would you recommend? My other frames were too old (not slot style) or had a clearance issue. Thank you in advance.

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Re: Hub Motor on skewer front fork?

Post by 99t4 » Apr 26 2022 1:47pm

You'll get some better advice if you can include some photos of what you're working with.

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E-HP   1.21 GW

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Re: Hub Motor on skewer front fork?

Post by E-HP » Apr 26 2022 2:26pm

Brockster wrote:
Apr 26 2022 12:02pm
I have a Specialized Hardrock from around 1995, give or take a few years. I bought a front hub motor from Battery Clearance House :thumb: and actually got it on the front fork. I have two nuts, one for each side. Since this fork had a skewer-style axle on it, can I use the hub motor with it? If yes, how many nuts, washers etc. would you recommend? My other frames were too old (not slot style) or had a clearance issue. Thank you in advance.
You need at least a washer on the inside of the fork dropout on each side, since the shoulder between the flat cut portion of the axle and the rest has a very narrown engagement surface. On the outside of the dropouts, it depends on how much axle you have to work with and after including a torque arm, which is you may either need one or two of, depending on how much power/torque the motor has.


https://www.ebikeschool.com/install-hub-motor-washers/

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Chalo   100 GW

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Re: Hub Motor on skewer front fork?

Post by Chalo » Apr 26 2022 2:27pm

The fork you have is fine, but you need to use tabbed washers so you don't spin the axle. Like this:

Image

I use a C washer (ready made or cut and filed from a regular washer) on the inside of the fork tip on the cable side, to provide some room for the cable so it doesn't get pinched. Then I use a tabbed washer on the outside, followed by the axle nut. On the opposite side, I use the tabbed washer inside the fork tip, with a plain washer and nut on the outside.
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Re: Hub Motor on skewer front fork?

Post by Brockster » May 02 2022 10:49am

Thank you for the advice! I also purchased torque arms already. :thumb:

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Re: Hub Motor on skewer front fork?

Post by docw009 » May 08 2022 4:12am

You can't use the anti-tamper nuts that came with the motor, unless you have the wrench that goes with it.

You can get conventional M12-.1.25 flanged nuts at Lowes, Ace Hardware (maybe), and online, but not at Home Depot,

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Re: Hub Motor on skewer front fork?

Post by calab » May 08 2022 11:58pm

For low power (~500w) the flanged/knotched washers are good but still why risk it?
I would never use them even on 250w wimpy UK power setups.
My ebike is to precious as a valuable day to day tool and no I dont care about the looks of my ebike.
I dont want much down time for a spun axle, which destroys the bikes dropout, alright for a front fork but a rear :shock:

Buy or make real torque arms
If you are scared off by the price of real torque arms (~$15-25) then it costs you literally nothing to make your own torque arms out of steel and a grinder, make it as vain and flashy as you want or as humble as you wish to be.

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Chalo   100 GW

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Re: Hub Motor on skewer front fork?

Post by Chalo » May 09 2022 1:02am

calab wrote:
May 08 2022 11:58pm
For low power (~500w) the flanged/knotched washers are good but still why risk it?
I would never use them even on 250w wimpy UK power setups.
I've installed more front Jump motors (and a few Ebikeling ones) than I can keep track of, all with two tabbed washers each. No problems so far, which is a lot more than I can say for torque arms I've installed. The vast majority of these setups have had 48V x 22A controllers running unrestricted.

One thing the tabbed washers have in their favor is that they fit closely to the axle, unlike most torque arms. They are also made of hard material, unlike most torque arms. Some of the same motors with which I've had no trouble from tabbed washers, have cut their threads though the flats on cheesy torque arms. So, I say why risk it with the typical torque arms such kits have? Grin torque arms work fine, but then so do tabbed washers.

You can't put a front hub motor on just any old fork; it's got to be steel and the tips should be substantial. I think it helps greatly to have a hub with a one-way clutch or at least no electrical braking going on.
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Re: Hub Motor on skewer front fork?

Post by amberwolf » May 09 2022 12:44pm

Chalo wrote:
May 09 2022 1:02am

One thing the tabbed washers have in their favor is that they fit closely to the axle, unlike most torque arms. They are also made of hard material, unlike most torque arms.
Do you happen to have an idea what they made them from/how? They appear to be cast, or sintered; but I am no expert.

They certainly do work well--I'm using a pair of them from one of those Jump motors on the SB Cruiser trike now, on an old A2B Metro Ultramotor driven by an external sensorless 40A controller on 14s. (because the axle is so good on those Ultramotors it actually cut into my clamping dropouts, "threading" them, so hopefully these tabbed washers will help prevent that until I make a better solution--previous motors, like the MXUS3k (450x) just broke their axles instead). Haven't tested them with motor braking, and don't intend to...but if the emergency circumstance arises (as it did when the cutting occured) we'll see how they hold up. ;)
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Chalo   100 GW

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Re: Hub Motor on skewer front fork?

Post by Chalo » May 09 2022 1:28pm

amberwolf wrote:
May 09 2022 12:44pm
Chalo wrote:
May 09 2022 1:02am

One thing the tabbed washers have in their favor is that they fit closely to the axle, unlike most torque arms. They are also made of hard material, unlike most torque arms.
Do you happen to have an idea what they made them from/how? They appear to be cast, or sintered; but I am no expert.
It's a worthy question I can't answer. But they're harder than cheese-grade Chinese torque arms for sure.

I've been having trouble lately getting my hands on such washers at a reasonable price. Two AliExpress sellers in a row have offered "front" washers, used a picture of the correct item in their listing, and then sent me washers that don't work with fork tips. And then insisted with me that they were the thing I'd ordered. That's $70 down the toilet so far for washers I can't use.
IMG_20220505_084544820.jpg
IMG_20220505_084544820.jpg (586.85 KiB) Viewed 223 times
I can find the right washers from USA sellers for ludicrous amounts of money, or I guess I could keep taking my chances with different Chinese fraudsters. It would be nice if I could just buy them at hardware prices, though.
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Re: Hub Motor on skewer front fork?

Post by amberwolf » May 09 2022 7:53pm

Chalo wrote:
May 09 2022 1:28pm


I've been having trouble lately getting my hands on such washers at a reasonable price. Two AliExpress sellers in a row have offered "front" washers, used a picture of the correct item in their listing, and then sent me washers that don't work with fork tips. And then insisted with me that they were the thing I'd ordered. That's $70 down the toilet so far for washers I can't use.

IMG_20220505_084544820.jpg
I don't have the tools to do it, but it should be possible to fold the angled tab down flat onto the washer part, though I don't know how well the bent part will take that kind of forming. It isn't the same as the ones that we know work, but it would be better than nothing (but it is probably not worth the labor of doing it).
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Re: Hub Motor on skewer front fork?

Post by calab » May 09 2022 9:01pm

https://youtu.be/c96n0Ma2rLY?t=1139
23:00 on those lipped washers

Lipped washers OK up to 40Nm, with steel rim it can handle more power, look at the graph.
Fork itself can vary but usually fails at about 40-50Nm others 90-100Nm
Wrench as tight as you can on the axle nut, is about 60-70Nm

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Re: Hub Motor on skewer front fork?

Post by spaceship » May 13 2022 2:16pm

Chalo wrote:
May 09 2022 1:28pm

I've been having trouble lately getting my hands on such washers at a reasonable price. Two AliExpress sellers in a row have offered "front" washers, used a picture of the correct item in their listing, and then sent me washers that don't work with fork tips. And then insisted with me that they were the thing I'd ordered. That's $70 down the toilet so far for washers I can't use.

IMG_20220505_084544820.jpg

I can find the right washers from USA sellers for ludicrous amounts of money, or I guess I could keep taking my chances with different Chinese fraudsters. It would be nice if I could just buy them at hardware prices, though.
Which AliExpress sellers did you try? I just ordered 2 sets from here

https://www.aliexpress.com/item/1005003 ... f9%21%21sh

Hopefully not one of the same ones who send you the wrong washers... I will report back when they arrive.

I am in the same boat debating whether to pick up a hardware set (m12x1.25 nuts, tabbed washers, flat washer) from Hilleater.com for $19 CAD plus a drive to Saltspring Island to pick them up. From what I've heard its a nice place to check out so could be worth it for the day trip on my motorcycle alone.

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Chalo   100 GW

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Re: Hub Motor on skewer front fork?

Post by Chalo » May 13 2022 3:05pm

spaceship wrote:
May 13 2022 2:16pm
Chalo wrote:
May 09 2022 1:28pm
Two AliExpress sellers in a row have offered "front" washers, used a picture of the correct item in their listing, and then sent me washers that don't work with fork tips.
Which AliExpress sellers did you try? I just ordered 2 sets from here

https://www.aliexpress.com/item/1005003223662932.html
I haven't tried that seller. I was taken for a ride by "MORIEN Store" and "SportbetterLife Store".
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Re: Hub Motor on skewer front fork?

Post by Mclewis1 » May 14 2022 7:55am

Chalo, Can you at some point in the future post a pic with the two different types of "front washers"? I'm guessing that it's a bent tab vs an elongated tab, but I'd like to see the differences. My only experience with them are those included in the Grin front wheel kits. Those, a tight front axle nut and nice beefy steel dropouts (on a Surly) have so far been bullet proof with a smaller hub motor, a Shengyi SX run with up to 1000w, so I'm guessing less than 50nm.

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Chalo   100 GW

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Re: Hub Motor on skewer front fork?

Post by Chalo » May 14 2022 9:32am

Mclewis1 wrote:
May 14 2022 7:55am
Chalo, Can you at some point in the future post a pic with the two different types of "front washers"? I'm guessing that it's a bent tab vs an elongated tab, but I'd like to see the differences.
Right kind:
IMG_20220505_084412126.jpg
IMG_20220505_084412126.jpg (1 MiB) Viewed 94 times
Wrong kind:
IMG_20220505_084544820.jpg
IMG_20220505_084544820.jpg (586.85 KiB) Viewed 94 times
Both kinds:
IMG_20220514_092422290.jpg
IMG_20220514_092422290.jpg (688.83 KiB) Viewed 94 times
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Mclewis1   100 mW

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Re: Hub Motor on skewer front fork?

Post by Mclewis1 » May 14 2022 1:57pm

Thought so ... thx

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