Front hub conversion on vintage delivery bike. Battery suggestions and best motor query

Nealh

Esteemed Pedelecer
Aug 7, 2014
16,985
6,638
59
West Sx RH
The RD5 is for 135mm OLN/drop out size yours is shy by 20mm, certainly one wouldn't spread the drop out on such an aged bike.
The X-RD3 70mm or 90mm drum version is for 117.5/118 mm OLN so one will be ok with just 2.5/3 mm stretching. One will have to settle for 3 spd with drum to keep the bike looking to outwardly modern with external gearing.
 
Last edited:

Rocket Raccoon

Pedelecer
Feb 10, 2020
33
6
The RD5 is for 135mm OLN/drop out size yours is shy by 20mm, certainly one wouldn't spread the drop out on such an aged bike.
The X-RD3 70mm or 90mm drum version is for 117.5/118 mm OLN so one will be ok with just 2.5/3 mm stretching. One will have to settle for 3 spd with drum to keep the bike looking to outwardly modern with external gearing.
OLD = Over Locknut, got it now thanks. Yes looks like you are correct if I want a rear drum. Might need a bit more power from the motor / controller with only 3 speeds though? (Will be used on some fairly gentle hills but also dont want to be peddling like a lune on the flat / downhill.) I guest that also raises another question, front and rear sprocket sizes. Spec for the RD£ says can accept from 13 - 24 teeth?
 

RogerA

Finding my (electric) wheels
Jun 21, 2021
21
8
It's possible to put 2 sprockets on a sturmey hub to give you an extra gear range. It usually has a 1/8" sprocket and 1/16" spacer. If you remove the spacer you can use 2 3/32" sprockets (eg I have a 15t and 20t on an old raleigh twenty to effectively make it A4 speed with all equal steps). The larger sprocket needs to be a double dished type. You would need some form of chain tensioner, but could then either change gear by manually moving the chain when needed, or fit a cheap old derailleur and shifter. I've used an old short cage 5 speed derailleur ( widened by the addition of a washer on the jockey wheels), and a friction shifter mounted under the saddle on the seat stay. It may spoil the vintage look slightly, but if you went for a tensioner and manual chain shifting it would take some close inspection to notice it.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
16,985
6,638
59
West Sx RH
I would opt for 44 or 48v if possible , the former means usally a bespoke or home welded/mad pack. A heavy motor like a BPM is 4.4kg so one has to think about how much weight on the front, ideally it needs a good steel fork then one shouldn't need torque arms, other wise opt for may be an AKM 100h/sx .
The sx variant is marked/rated 250w the h isn't.

For such a bike one expects a 201rpm will be best for a heavy bike, downhill one could freewheel almost as the bikes mass will help.
Most hubs have high internal gearing 4.4 or so with the lighter hubs they tend to be a bit higher geared the AKM100SX 12.6 in 201rpm form.
 
Last edited:
  • Like
Reactions: Rocket Raccoon

Rocket Raccoon

Pedelecer
Feb 10, 2020
33
6
It's possible to put 2 sprockets on a sturmey hub to give you an extra gear range. It usually has a 1/8" sprocket and 1/16" spacer. If you remove the spacer you can use 2 3/32" sprockets (eg I have a 15t and 20t on an old raleigh twenty to effectively make it A4 speed with all equal steps). The larger sprocket needs to be a double dished type. You would need some form of chain tensioner, but could then either change gear by manually moving the chain when needed, or fit a cheap old derailleur and shifter. I've used an old short cage 5 speed derailleur ( widened by the addition of a washer on the jockey wheels), and a friction shifter mounted under the saddle on the seat stay. It may spoil the vintage look slightly, but if you went for a tensioner and manual chain shifting it would take some close inspection to notice it.
Thanks, will give that some thought. It is already maybe going to be a bit "busy" back there with the gear and brake cabeling though!
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
16,985
6,638
59
West Sx RH
Gearing will have to be played with both front and rear, one can change the front chainring possibly if using a modern BB or spider and the rear play with sprocket sizes if using for inclines. Ulitmately you are going to have to sacrifice speed for lower gearing most likely for an easier ride, high cadence will be better for the knees on the flat and the motor will be doing most of the work. With the hub motor the lower the gearing the more torque one will feel as well as they don't like being laboured or stalled.

Rear sprocket wise a higher tooth number will be better then alower one.
Use the gear calc to see how one can model the gearing for speed etc.
Bicycle Gear Calculator (gear-calculator.com)
Select the SA s3 for the drive.
 

vidtek

Esteemed Pedelecer
Mar 29, 2015
315
153
71
Bournemouth BH12
Good luck with your bottom bracket. I resurrected a 1986 Specialized Crossroads from a charity cycle shop and fitted a mid-drive. I was unable to shift the bottom bracket at all. In the end I took it back to the shop and 2 mechanics with a railways issue 4 ft spanner finally managed to shift it after many heating/cooling cycles.
 
  • Like
Reactions: Bikes4two

Rocket Raccoon

Pedelecer
Feb 10, 2020
33
6
Good luck with your bottom bracket. I resurrected a 1986 Specialized Crossroads from a charity cycle shop and fitted a mid-drive. I was unable to shift the bottom bracket at all. In the end I took it back to the shop and 2 mechanics with a railways issue 4 ft spanner finally managed to shift it after many heating/cooling cycles.
Yep, I may have a crack at it today. Will keep you posted! (Went to a local bike shop to order new headstock bearings and cups this week. He said the same kn the BB. He ended up having a bar welded onto the nut to free it off!
 
  • Like
Reactions: Bikes4two

Nealh

Esteemed Pedelecer
Aug 7, 2014
16,985
6,638
59
West Sx RH
There should be an english thread on both sides so the crank arm and chain ring should come off, behind the chain ring should be another threaded bearing holder similar to the one on the lhs.
Bearings should be old money so 1/4", replace all after a degrease and clean.

Crank & chain ring might be one piece also may be rusted on ? Try plenty of penetrating oil and tapping off or apply the heat snd cooling method to see if it will budge.
 

Rocket Raccoon

Pedelecer
Feb 10, 2020
33
6
There should be an english thread on both sides so the crank arm and chain ring should come off, behind the chain ring should be another threaded bearing holder similar to the one on the lhs.
Bearings should be old money so 1/4", replace all after a degrease and clean.

Crank & chain ring might be one piece also may be rusted on ? Try plenty of penetrating oil and tapping off or apply the heat snd cooling method to see if it will budge.
Thanks! So crank and chain ring should just pull off like the other side so I can get to the other bearing? Its very tight. Might have to get a puller of some sort....
 

sjpt

Esteemed Pedelecer
Jun 8, 2018
3,063
2,308
I like your project, good luck.
Most so called 'advances' to bike technology make me feel 'so what?', but I'll certainly be happy if I never have to deal with a cotter pin chainset again.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
16,985
6,638
59
West Sx RH
It is most likely rust holding the crank/ chain wheel on esp as the cotter pin is out. Have to admit I hated cotter pins and still have the scars on my ankle from 50 years ago as a kid.
 
Last edited:
  • Like
Reactions: Rocket Raccoon

guerney

Esteemed Pedelecer
Sep 7, 2021
4,090
1,441
So I got this far by simply unscrewing the LH side of the bottom bracket assembly, surprisingly easily! How does the shaft come out though???
It is most likely rust holding the crank/ chain wheel on sesp as the cotter pin is out.
If there's nothing else keeping it on and it's stuck with rust, and you are completely stuck having tried penetrating oil, applied heat/cold, tapping and time, and you've exhausted all other options... you may have to do as I did? Find a plank of scrap pallet wood, drill a hole large enough to securely hold a metal butt of some kind (I used a ruined crank extractor), stick that into the hole in the plank, so that it stands vertical. Then place the shaft over it and carefully hammer around the shaft on the other side, until the shaft comes out. At least, that's what I was advised to do by the 100 year wizened old local bike shop Yoda: "If I may make a suggestion? Place it over a metal butt of some kind, and hammer like hell!" He also said because I wasn't an existing customer, he couldn't find time to do it for me. Said he had too much work on anyway - I'm certain he had a puller. It took about two hours of alternately tapping and hammering like hell to get that baby out! Do hammer carefully. I didn't have a wooden mallet but that would probably be a more appropriate tool than the claw hammer I used. Solid gold advice that was, from the bike shop Yoda.
 
Last edited:
  • Like
Reactions: Rocket Raccoon