View Full Version : sturmey archer mid-drive problem

09-07-2011, 07:59 PM
First of all kudo's to such a great site and such a great community.

I have been absent for some months but my mom and sister now have newer rebuilt and reliable cars and I can now finally move my 80% done warrior back to the front burner.

First what is the most acceptable way of posting pics too the forums? I think this would be helpful.

Second, Does anybody know of a bike shop (hopefully online) that has expertise in sturmey archer products and problems?

Thirdly, here is my problem. My rear gears (8 gear 13/34 Meagdrive) and Derailleur as well as my front crankset are mtn bike fare. These are designed for 3/32" chain.

For a Mid-Drive I am using a sturmey archer SRC5 (W) hub that "Staton Bike" sells as a transmission/Mid-Drive. The gears that are included are for a 1/8" chain. The 3/32" chain will not fit the Sturmey Archer gears.

I believe that places such as Harris Cyclery sell 3/32" input gears that will fix the input side of my Mid-Drive problem but the output gear is truly my issue.

There seems to be little hope of assistacce from Staton so I am turning to my fellow Zombies for help.

I have read that a 1/8" chain will work with components such as these but I am truly trying to refine my drivetrain not just get it to work.

In a perfect world I would have a duplicate of my output gear but for a 3/32" chain but I don't want to molest the only gear that I have that sort can be made to work.

I do not have access to a machine shop but I am thinking of ways to machine out the center of a 22 tooth gear (sourced from *** knows where) drill 9 holes to attach it to the spoke holes which is how the present one is attached.

I have read that a 1/8" chain will work with components such as these but I am truly trying to refine my drivetrain not just get it to work.

I am hoping for a more elegant solution, any help or suggestions would be appreiated.


09-08-2011, 06:03 AM
First steps first; Conversion for us logically inclined.. ;)
3/32" = 2.3813mm ~ 2.4mm
1/8" = 3.1750mm ~ 3.2mm
Your gears are designed for a 2.4mm chain, your mid-drive has got gears for a 3.2mm chain. Have I missed something?

What would prevent you from using the 3.2mm chain all over the place?

09-08-2011, 07:58 AM
I have concerns about if a .8mm wider chain will be as smooth through the derailleur and if the wider chain will shift as smoothly on an 8 gear freewheel. Seems to me that the wider chain might rub on the derailleur cage and on the adjascent gear ramps. If this happens it would likely cause drastically lower efficiency, wear parts and make annoying sounds.

I don't know if this will actually be a problem in practice and have never run into this before. I am willing to try it if the concensus is that it will likely fly.

I have found and ordered new 3/32 gears from smartbikes.com. I still dont know how i'm going to concentrically enlarge the hole to the required diameter butif all else fails careful work with a carbide burr might do the trick.

Opinions on all this is quite welcome.

Thanks Siggurd

09-08-2011, 08:22 AM
I see.
The derailleur might be a problem as you suggest. The thinner chains are usually designed to "bend" a bit more than the thicker ones.

Can you grind down the current sprockets from 3.2 to 2.4mm? See if you can mount them on something that's spinning and then use an angle grinder (with a flap-disk) to thin them down? 0.4mm per side is not that much. Best would obviously be if you could take the sprockets to someone who's got a lathe and turn them down carefully.

09-08-2011, 08:48 AM
Hello Siggurd
I am not familar with the sturmey archer hubs. And I am unsure where you are located. However here a link to a USA service center for internal hubs. (www.rideyourbike.com/internalgears.shtml) Maybe they could help with gear conversion. Alternatively you could pull the gears and find a machine shop to cut you 3/32 chain tooth gear that would remount to the hub. Or buy gears 3/32 toothed gears from a source such as (www.niagaracycle.com) and maybe hand file the opening to mount to the Sturmey Archer hubs. Another alternate would be to buy a couple gears and build yourself an adapter to mount to the present gears using stand off's and screws so it can be remove and reused with a 1/8 chain in the future. This is a couple ideas. Best of luck.

If there is a will there is a way.

09-08-2011, 12:34 PM
If you use the 1/8" chain, you can widen the derailler by adding washers to the derailler wheels. Sometimes it works, sometimes it doesnt.
Other alternatives include welding a larger 3/32 cog to the 1/8" cog, or carefully grinding each tooth of the 1/8" cog.

09-09-2011, 12:15 AM
Ok, thanks for the suggestions. I have ordered a few gears from smartbikeparts. One is a flat 22 tooth gear that I hope I will be able to bore the center out of. Since the gear is the correct thickness, I find this to be more promising than trying to thin out the existing gear. So my plan is to bore/ grind the center hole out to the correct diameter and carefully use the old gear as a drilling template/guide to locate the mounting holes. With shipping and such and a recent leg infection that I just now got antibiotics for I don't suppose I will have results before mid to late next week but I will update when I have something.

This is the last real obstacle between now and a real shakedown cruise wish me luck and thanks for all the input.


09-09-2011, 12:18 AM
BTW Darnthedog. Thanks a bunch for the link. I think this will come in very handy. I think I might become addicted to IGH's


09-15-2011, 09:18 PM
Still waiting for the gears that I ordered a week ago fromsmartbikeparts. Nice guy but not very responsive. Got tired of waiting so I ordered another from bikesmith designs. Looks like another week before I post anything interesting.

09-18-2011, 06:30 AM
Hope you get the bits soon!

10-02-2011, 08:39 PM
I got over an illness which kept me in bed for 4.5 days. But before that I got my warrior in ridable condition. I got tired of waiting for smartbikesupply so I ordered a couple from Mark stonich @ Bikesmith Design and Fabrication. He seems a bit Zombish and I got the gears in a couple of days.

Here is the the original on the right, the purchased one in the center and the hacked one on the left. I had to anneal it before i could easily drill the holes but it all works very well now.

With 18.5 to to 124.2 gear inches I think I got it all covered. I temporarly set up my computer to the rear wheel on a stand and informally counted 60 rpm @ the pedals which added up to 25=+mph.

I rode it about 15 miles before I got sick and I am sure people have said it so many times before but "Man is this thing fast". It is comfy, even over rough roads. The brakes are awsome (I will never be w/o discs again).

Now I gotta make my permanent handlebars so that I can run my cables better (My IGH is very stiff to shift due to routing I hope).

I also have a very cool power idler hack but I think that would be best in another post so that all may find it.

Thanks to all for the advice, more to come in other posts.