DD Hub as a mid drive motor pros and cons?

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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minde28383   10 kW

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Re: DD Hub as a mid drive motor pros and cons?

Post by minde28383 » Dec 27 2020 2:42am

Regarding ''plate with the 44mm 6 bolt pattern to fit the disc rotor interface".

yes, but consider few hundred Nm on these six 5mm bolts. [If these bolts where at least 6mm...] This adapter has to be the same thickness as brake rotor or barely thicker (everything is cramped there). Brake rotor (adapter) Inside diameter is quite big therefore we are looking to sprockets 30t and up therefore we need to increase rear sprocket too to get that needed ratio. If we do 1:2 than rear sprocket over 60t which gets unaesthetically.
Keeping that 1:2 with 19t and 38t would be much better.

It would be nice to attach 15t-19t sprocket to qs205v3 hub.
19t 428 sprocket has 81mm/82mm outside diameter.

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ferret   1 kW

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Re: DD Hub as a mid drive motor pros and cons?

Post by ferret » Dec 27 2020 2:43am

veloman wrote:
Dec 26 2020 1:17pm
Is there an off the shelf sprocket that can mounted to the 6 bolt disc rotor holes? Or are the guys building these mid drives customizing motorcycle sprockets to fit on the hub side cover?
https://www.velosolo.co.uk/shopdisc.html
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minde28383   10 kW

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Re: DD Hub as a mid drive motor pros and cons?

Post by minde28383 » Dec 27 2020 2:52am

I made ~19t (updated teeth number) 428 sprocket sketch from paper over brake rotor. Precision is not there lightly to say, but no strength to do any sketch with AutoCAD lately.
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minde28383   10 kW

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Re: DD Hub as a mid drive motor pros and cons?

Post by minde28383 » Dec 27 2020 3:18am

ferret wrote:
Dec 27 2020 2:43am
veloman wrote:
Dec 26 2020 1:17pm
Is there an off the shelf sprocket that can mounted to the 6 bolt disc rotor holes? Or are the guys building these mid drives customizing motorcycle sprockets to fit on the hub side cover?
https://www.velosolo.co.uk/shopdisc.html
pitch is the same as 420 and 428 but these sprockets are thin bicycle sprockets. Adding few of these would increase thickness but not sure if there would be possible to install due limited space between cable. Maybe it is possible but I see tenancy to install sprockets on other side of a hub.
Adapter could be less thickness than of a 428 sprocket but machining is needed.

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minde28383   10 kW

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Re: DD Hub as a mid drive motor pros and cons?

Post by minde28383 » Dec 27 2020 3:30am

To make it proper way new hub cover has to be CNCed. Other side than phase cables. Than it would be possible to install quite small sprockets, maybe ~20teeth.

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Chalo   100 GW

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Re: DD Hub as a mid drive motor pros and cons?

Post by Chalo » Dec 27 2020 3:51am

ferret wrote:
Dec 27 2020 2:43am
veloman wrote:
Dec 26 2020 1:17pm
Is there an off the shelf sprocket that can mounted to the 6 bolt disc rotor holes?
https://www.velosolo.co.uk/shopdisc.html
Those are fine, but you don't get much reduction ratio that way.
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veloman   1 GW

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Re: DD Hub as a mid drive motor pros and cons?

Post by veloman » Jan 02 2021 4:51pm

by Chalo » Dec 27 2020 3:23am
"If it were me, I'd make a plate with the 44mm 6 bolt pattern to fit the disc rotor interface, and a 74mm or 110mm 5 bolt pattern to fit any one of a number of chainrings. 74mm for rings under 34t, or 110mm for rings from 34t up. It would be easy enough to get it laser cut, or else drill it using an indexing head.

Modifying a sprocket means having to throw that work away when the sprocket wears out."


Ah yes, good thinking.

My application for this is not a bike. I'm mounting a hub motor to drive an axle on a small tractor I'm building. I need a 5:1 reduction for my goal machine speed of 4mph under load. It would have been easier to use a 3kw Cyclone motor with gearbox, but the hub motor I got ended up being a very fast wind, so it negated the lower rpm advantage I thought I was going to have. Both spin around 900rpm on 72v.

I'm excited to see the torque I'll have with 3kw at 4mph. :D
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