Advice on Donor bike for rear hub conversion - Downhill Full Susp

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beyondr9k   1 µW

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Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by beyondr9k » Apr 30 2021 3:42am

Hi guys I'm quite new to the sphere so excuse any naivety...

Been dreaming of tackling a project like this for about a year now and about to pull the plug on a donor bike.
An Iron Horse Sunday downhill full suspension bike has popped up in my area and i'm wondering whether it'll suit my prospective build. Looks to be a very reinforced Aluminium frame sitting at ~20kg with enough inner triangle space for mounting. I believe it's also a through-axle. I'm still quite confused with the dropouts lingo and would love some advice on whether this would be appropriate to purchase.

Basically wanting to do:
- MXUS 5KW Turbo V3 rear hub motor DD
- unsure on controller
- I intend to make the battery pack myself with 18650s

With the outcome basically being a weaker Stealth Bomber B-52 I can take out on trails and in the city (hopefully without too much suspicion by the police)

budget is around $3000AUD but I'm wanting to buy the bike now to ease into downhill riding as I won't have the time for the project till my University break (studying Engineering)

Otherwise, would something like a Giant Trance/Anthem be suitable? Heaps seem to pop up used in my area

Thanks fellas :)
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Voltron   1 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by Voltron » Apr 30 2021 4:42am

The thru axle design won't work with a hub motor.

markz   100 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by markz » Apr 30 2021 1:45pm

Voltron wrote:
Apr 30 2021 4:42am
The thru axle design won't work with a hub motor.
Thru axle will work with only one hub motor.
Grin All Axle hub motor
https://ebikes.ca/grin-all-axle-hub-standard-wind.html
However there are various diameters of thru axle in the bicycle industry itself.
The quick search did not reveal the size of thru axle on all axle hub.

Voltron   1 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by Voltron » Apr 30 2021 1:51pm

He specified an MXUS motor, that won't work, but yes, I was being overly broad re all hub motors.

markz   100 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by markz » Apr 30 2021 2:22pm

Well I was just suggesting that there was a thru-axle motor that is available.
I like how we justify on both our parts.
Its an interesting human characteristic, more exemplified and exaggerated online.
I wouldnt have posted this thread otherwise.
All I am just saying is I could have perhaps done my original post in a different way, made more of an explanation, made a longer post, did some quotes of the OP. It would have taken up as much time as clicking Submit on my post here.

edit
But I feel as though I should ad more value to this post.
I dont know who said it, maybe it was Nep, maybe it was probably more Justin but with the way the bike industry is going in general, there should be more hub motors with thru axles. Just like hub motors should deviate away from freewheels to cassette but profit margins tell the story. Well we could open a big bag of discussion on what I typed there, but shall leave it there.

Voltron   1 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by Voltron » Apr 30 2021 2:37pm

We're all just here to help👍

And it would be nice to see more motors that aren't true thru axle maybe, but solid axle tapped on both ends for bolts, and an integrated torque arm like the old Heinzmans, that would fit into newer frame.

Grantmac   10 kW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by Grantmac » Apr 30 2021 10:19pm

How aggressively do you intend to ride off-road?

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MadRhino   100 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by MadRhino » Apr 30 2021 10:28pm

Voltron wrote:
Apr 30 2021 4:42am
The thru axle design won't work with a hub motor.
Just every bike that I have built in the last 12 years were through axle, all of them built with big DD hub motors fed high power.

Through axle is a standard in DH bikes for a long time. Powerful ebikes require custom dropouts anyway. We couldn’t care less about through axle since we need to cut them, or use them as part of the mount for custom dropout plates.
Make it fool-proof, and I will make a better fool.

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E-HP   100 MW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by E-HP » May 01 2021 10:00am

MadRhino wrote:
Apr 30 2021 10:28pm
Powerful ebikes require custom dropouts anyway. We couldn’t care less about through axle since we need to cut them, or use them as part of the mount for custom dropout plates.
It looks a bit challenging with this frame, as far as easy ways to mount the plates, but if not, it would be nice to see how they'd be fitted/attached, since that would provide a lot more options when looking for frames,

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MadRhino   100 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by MadRhino » May 01 2021 11:31am

E-HP wrote:
May 01 2021 10:00am
MadRhino wrote:
Apr 30 2021 10:28pm
Powerful ebikes require custom dropouts anyway. We couldn’t care less about through axle since we need to cut them, or use them as part of the mount for custom dropout plates.
It looks a bit challenging with this frame, as far as easy ways to mount the plates, but if not, it would be nice to see how they'd be fitted/attached, since that would provide a lot more options when looking for frames,
Well, depends of the year. It was made 135 mm and 150 mm. The older would need to mount the custom dropout plates on the outside to fit a big hub, not as easy as the later that could accommodate them on the inside flat surface. Still, the outside surface could be shaved snd filled in order to make an easy fit. The through axle hole can be used for a mounting screw of chainring type, plus two smaller ones to make a solid mount. The dropouts would be extended to a few inches to the rear, which is desirable when feeding high power to a compact frame.

Another, more expansive solution, is to cut and weld the alu in order to make a mount for through axle dropout plates. This kind:
DB86DF90-AE35-4F77-95DC-83CFFE8D9C68.jpeg
DB86DF90-AE35-4F77-95DC-83CFFE8D9C68.jpeg (1.35 MiB) Viewed 193 times
637A5B59-5B10-4ED2-9996-F9EC4F7F0148.jpeg
637A5B59-5B10-4ED2-9996-F9EC4F7F0148.jpeg (64.85 KiB) Viewed 193 times
Make it fool-proof, and I will make a better fool.

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E-HP   100 MW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by E-HP » May 01 2021 11:45am

MadRhino wrote:
May 01 2021 11:31am
Another, more expansive solution, is to cut and weld the alu in order to make a mount for through axle dropout plates. This kind:
DB86DF90-AE35-4F77-95DC-83CFFE8D9C68.jpeg

637A5B59-5B10-4ED2-9996-F9EC4F7F0148.jpeg
With the contours of the frame the OP is using, it looks like the cut and weld would be easiest, assuming access to a tig welder.

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MadRhino   100 GW

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Re: Advice on Donor bike for rear hub conversion - Downhill Full Susp

Post by MadRhino » May 01 2021 1:58pm

E-HP wrote:
May 01 2021 11:45am
MadRhino wrote:
May 01 2021 11:31am
Another, more expansive solution, is to cut and weld the alu in order to make a mount for through axle dropout plates. This kind:
DB86DF90-AE35-4F77-95DC-83CFFE8D9C68.jpeg

637A5B59-5B10-4ED2-9996-F9EC4F7F0148.jpeg
With the contours of the frame the OP is using, it looks like the cut and weld would be easiest, assuming access to a tig welder.
Welding custom mounts is always more expansive and complicated. It does require to make a jig first, and after the mounts are welded the swing arm need to be cooked in an oven and mechanically aligned, essential to restore the frame symmetry and alloy hardness.
Make it fool-proof, and I will make a better fool.

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