-Sturmey Archer IGH for mid drives-

[waynebergman]

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Thinking of switching over from the deraileur system to a Sturmey 3 speed IGH. I good initial success with tweeking my drive train for a 4 speed deraileur system but the 42 tooth rear cog collapsed under power the other day so thinking of other options.The plan is to shop for a SX-RK3 IGH running a 22 tooth rear cog and replace my 42 tooth luna front ring with a luna 30tooth mini. This will give me the same one to one ratio in first gear that I had with the 42 up front and the giant 42 cog on the rear.
I have a few questions please as there are a few things I am not sure about and don't want to buy the wrong stuff.....

1.If I go with a 22 tooth rear cog shown in the photos I see there is an option for 1/8" steel. I should know this but I cant remember if this would be compatible with 8 speed chain or do I need BMX chain?
2.If I need to run BMX chain then I am wondering if that BMX chain would be compatible with the little luna 30 tooth mini?
3.I have one of the parts circled in red that comes with the hub kit that I am wondering if it will clear my drop out assembly? If these little arms need to be bent to clear the drop outs is that OK? I am not familiar with these IGH's so not sure how important it is too keep this little arm exactly like it is. I may run into clearance issues so I figure I may have to bend it to make it fit around the protrution where the drop out meets the seat stay.I have also circled this area in red in the photo of my bike to show the area of concern.

many thanks..........wayne

 

[Fantomas]

For ebike new Sturmey-Archer RX-RD5

 

[waynebergman]

Thanks Fantomus but it looks like that hub is does not support disc mount so its pretty much out for me. Also I am not so sure that model would be as trouble free as the three speed I am looking at. I have not heard of anyone with a mid drive putting 1500 watts through this 5 speed so I feel more comfortable going by what others have had success with like the 3 speed. I do like the huge spread of the gearing however and it covers a big range which is nice. It would be good to know if anyone is using this hub with a 1500 watt mid drive?

 

[Fantomas]

http://www.sturmey-archer.com/en/products/detail/rx-rk5 for disc brake

 

[spinningmagnets]

Karl wrote a glowing review of the Sturmey SX-RK3 3-speed. Has disc mount and fits fat tires. So...your initial plan sounds good to me.

http://electric-fatbike.com/2016/01/16/sx-rk3-sturmey-archers-3-speed-igh-for-fatties-its-got-the-power-dum-dum-da-da-dum/

 

[Avitt]

I posted this a while ago. Don't know if the shifting mechanism for SA 3-speeds has been updated, but I doubt it.

Bottom line: I wouldn't even shift while under leg power...

Sturmey Archer 3 speeds typically use a "key" to select the gear. And this is what tends to happen, when shifted under load (borrowed picture, but this same thing happened to my S3X):

I wouldn't pair one with a mid drive...

 

[spinningmagnets]

It seems to be able to take more power than many other well-known IGH's. Its good to know ahead of time that it has that weakness of not being able to shift under power without accumulating damage, but...for some applications, it may still be an option. When driving manual-transmission cars and industrial trucks, I always let off the power when shifting (with one truck having over 750,000 miles on the manny trans when I moved to another job), however...I understand that many riders don't want to have to do that, especially if they frequently use PAS as their main throttle.

 

[turbo1889]

@Avitt

S3X is the three speed fixed isn't it?

Which does not have the same internals as the standard three speed which should still be old style four pronged sliding clutch shifting?

 

[WoodlandHills]

I am curious why you chose the Sturmey-Archer over the Shimano Nexus 3? I have a few hundred trail miles on my Nexus 3 with no problems at all, but I also have a SA 5-speed at my local wheel builder awaiting a compatible rim. The SA and the Nexus both have the same 25% gear steps and both have the middle gear as direct drive. In effect, the Nexus is a 3-speed SA, or the SA is a 5-speed Nexus! This is a new design hub from SA and it is supposed to be much more robust than their earlier designs. Time will tell, I am out of town for a week or so, but I plan to start to beat on it ASAP.

 

[Avitt]

@Avitt

S3X is the three speed fixed isn't it?

Which does not have the same internals as the standard three speed which should still be old style four pronged sliding clutch shifting?

Yes, you're right. The S3X is a fixed hub, which uses a selector key. It's not the same shifter mechanism used in the SX-RK3.

Thanks for pointing that out, and I'm sorry for causing any undue concern.

 

[waynebergman]

Woodlandhills, I am choosing the Sturmey as it has the 170mm sizing with the disc mount. I don't think the Shimano will work for 170mm spaced drop outs.

 

[waynebergman]

http://www.sturmey-archer.com/en/products/detail/rx-rk5 for disc brake
Fantomus the link above here you provided shows the width is not for fat bikes. 135mm spacing, yes it has disc but not wide enough so this is no good for me but thanks.

 

[tomjasz]

Anyone found stock on the sx-rk3?

 

[waynebergman]

I found one site in the UK but it was way too expensive and the shipping was also super expensive. Funny thing is they at least would ship it to me in Canada from the UK but most suppliers in the USA will not ship it to me in Canada even if they have availablity so I am having a dilly of a time finding one for a decent price and having it shipped to me in Canada. I have given up for now.

 

[waynebergman]

I am having difficulty finding any online suppliers that has a Sturmey-Archer SX-RK3 170mm Disc Hub in stock. If anyone finds a supplier that has stock could you please post an update on this thread, thanks.......wayne

Once I find a supplier and I order I will also get one of the 30 mini's from Luna. If I run my 42 eclipse up front the chain line to the IGH with one of its stock cogs the chain line will be no good so I may run the 30 tooth up front as it runs more out bound to match the stock cog placement on the IGH and then run a 22 tooth cog on the IGH hub.

One other option is to keep the 42 up front and try using a 30 tooth mini bolted onto one of the supplied rear cogs from Sturmey Archer. The reason I am thinking about the 30 tooth mini for the rear is it has an inbound offset that would better line up with my 42 tooth eclipse that I have already mounted up front for better chain line and get me closer to my one to one gear ratio in first gear from the 3 speed IGH.

I feel it will be better to have two larger sprockets that two smaller ones for the same gear ratio and I may be able to use some spacers and machine something up to adapt the 30 tooth mini to the sturmey archer supplied rear cog.

Thoughts welcome

 

[WoodlandHills]

I am not sure if the SX hub uses the smaller base ID SA sprockets like the narrower 3-speed model mentioned earlier or if it uses the larger ID base cogs like the 5 and 8 speeds. If it is the former, Shimano Nexus 3 sprockets are interchangeable with Sturmey-Archer cogs and are available in a large enough physical size to be able to modify.

I used the 24t Fichtel and Sachs cog you show in the very first post as a base since it was cheapish and available and I combined it with cheap steel 28t and a 32t BMX sprockets from NiagaraCycle.com. The two BMX sprockets are made from the same blank and have the same 5 holes around their diameter that I transferred onto the Shimano base. Then I used a scrap Shimano freehub body combined with a Park Tool bottom bracket tool as a mandrel to align everything before drilling. Be advised that the steel in the Shimano cog is very hard and unless you use a carbide bit in a drill press you'll only scratch it! With 5 matching holes on all three sprockets I can bolt either the 28t or the 32t to the Shimano base at any offset I choose by using washers between the sprockets. Be sure to have spare snap rings on hand: if they lose tension from being removed and reinstalled too many times, the sprocket will pop off of the hub. For this reason I keep several spares and discard them when they show a gap where the ends meet.

I combined the homebrewed 32t with 3 thick AN washers for offset and some AN #10 screws on the hub with a Lekkie 42t on the BBSHD to give an almost perfect chainline as well as very good performance on the trail with a Nexus 3.

But if you need the larger ID cogs like I do with my new SA 5-speed, the choice is a lot more limited. The largest I have found so far is the stock 25t from SA, fortunately it is available in an offset version to help with chain misalignment and is relatively cheap too. Unfortunately, they don't seem to have enough metal to use as a base for a similar modification.

 

[waynebergman]

Hey Woodlandhills, this is good info when I get around to sourcing out different cogs. I have ordered the 30 tooth mini from luna and now I will just wait until one of the suppliers that ship to Canada get stock in on the SA IGH. I need to go with a Sturmey IGH as I need 170 mm spacing and also disc compatible. Thanks a bunch!

 

[WoodlandHills]

I just got my 25t sprocket in the mail and an 8-speed Shimano cog will not fit my 5-speed hub. It looks like I will have to wait for SA to start importing their 25t off set cogs to get the best setup. Make sure you order by part number from SA, it seems they have several sizes of cogs.

 

[waynebergman]

I have found a source for the Sturmey Archer SX-RK3. Industrial Bicycles will have stock in a couple of days and then its in the mail. From them I could only get the 18tooth so I will shop around for a 22 tooth somewhere else. They want $152.00 for the hub and it comes with the trigger shifter so I am OK with that. I hope I don't get dinged too much for the shipping and duty.

 

[waynebergman]

Hey Woodlandhills, I am thankful for your info. I was coming up empty on finding a 3/32" 22 tooth SA cog that was dished. SA don't make them. But I was able to get a Nexus 22 tooth in a dished cog and for a decent price from Niagra like you recomend see attached photo. I am pretty sure it will fit the SA. Thanks again .....wayne

 

[WoodlandHills]

You can also get a 25t from the Bikesmith, but is pretty spendy compared to the SA and Shimano cogs. Still, I got one and am very happy with it.

 

[waynebergman]

Thanks Woody, your the man! The 22 in the rear with the 30 up front is going to give me the one to one gearing I want when in first gear so I am happy with the 22 for now. Awesome!

 

[WoodlandHills]

I will be following your build with this hub with great interest: my new bike has a 170mm dropout width like yours. It is my first deraileur-type ebike after two IGH ebikes and if it does not work out its good to know I can go back to what I am familiar with. I hope this size cog is the one that works on your hub since I have a full selection of them on hand from when I had two Nexus 3s. I will give the 10-speed cassette a good trial, but I really have learned to like an IGH.

 

[waynebergman]

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My SX-RB3 arrived in the mail today & it looks really shookum! A few photos above for reference on some questions I am hoping to get some insight on.

One picture shows the hub, Awesome I love this thing.
Next comes the instructions and they are confusing me.

One picture shows the instructions that came with the hub. The instructions on the Sturmey web site are worse because they show what is called a fulcrum lever (screen shot of those instructions also shown above) which is not part of my package. I have no long fulcrum lever which is confusing as this is what you would attach your gear shift cable ferrel to if you had this long fulcrum lever. At least that would be my guess. Maybe the little piece marked with the number 3 in my parts photos would be the item to attach to this fulcrum lever. The 3rd photo shows the parts that came with my hub the the number 2 on that photo shows the fulcrum lever that I have so its not like they forgot to send it, it appears they have a different system but no instructions as to how this new shorter fulcrom lever replaces the old one as there is no allowance to anchor my gear cable to it that is for sure.

One my instructions that came with the hub they say to line up this "Indicator" with the chain stay. This makes no sense as my frames shifting bosses are on my seat stays and not my chain stays. Also from the last boss on the seat stay closest to the axle it is meant to run cable housing the rest of the way to your deraileur if you are running one. So my best guess is way up the seat stay I run bare shifting cable with no housing from the seat stay boss exit down to the "Indicator Assembly" and then this would mean I would angle the Indicator assembly more upwards towards the seat stay? In the one photo with the pen markings on the paper the number 1 points to what they can the "Indicator". No where in the instructions do they make mention of how to conect the gear change cable to this assembly. I am also guessing the part with the number 3 pointing towards it is something to attach to maybe a cable boss but its threaded so I am totally confused. Yes I have been into my evening Ciders and its just about time for a refill but these instructions are not helping.

If anyone has a photo of how they hooked theres up especially around the axle and seat stay area would sure help me a lot.

If there are any Sturmey guys that have done this install and can help .....thanks

 

[WoodlandHills]

Wayne, I now understand what SA mean by my 5-speed hub being a "rotary" hub: the cable from my shifter wraps around the outside body of the hub and rotates an external lever to change the 5 gears. Yours appears to be more like a wide version of the SA 3-speeds we saw as kids on "English racers", if anyone can recall that term from my youth, where the cable terminates in a chain that changes 90 degrees as it enters the hub and gear changes are made by pulling the chain out of the hub against spring tension. My instructions made reference to a series of yellow marks on the outside of the hub that had to be aligned, but that was much more in the way a Nexus 3 is setup (the goal of all hub designers IMHO). Are your instructions referring to marks on the chain or the amount the chain is pulled out of the hub thus sliding internal cogs and changing gears?

Have you tried Sheldon Brown? He's my go to guy online for basic bike info and might have a generalized tuning guide......