S/A 3spd IGH to 8spd IGH questions

[Defjr333]

While this topic category has me confused as to whether it is for IGH's or Motorized Hubs with gearing, I will post here anyway.
I currently have a Sturmey Archer XL-RD3 IGH on the rear. It has a 90mm drum brake and 133% gear range, 3 speed Internally Geared Hub. 2nd gear is straight through 1:1 or 100%. Gear 1 and 3 are +/- 33% respectively. I have a 13 tooth cog on it driven by a 48 tooth Chainring up front. It decided to have issues and needs to be rebuilt or replaced. The damage is due to the way S/A designed the gear shift mechanism. The little chain indicator part snapped off inside the hub right at the thread line. After researching online, it seems this is a common failure, even when installed correctly(the 1/2 turn back off from fully tightened). It obviously has been such an issue that Sturmey re-engineered that part of their hub lines to a newer "rotor" style adjustment of gears. The newer design makes adjustments much easier and simpler, and no longer has any parts that protrude from the bike past the frame(other than the bolts on each side). On top of those 2 improvements, the "rotor" style is supposedly more robust and less prone to breakage. So, I have decided it is a better use of my money to go ahead and replace the hub instead of just rebuilding it. I could rebuild my current one for around $55. That is around half the cost of the hub itself. The hub I am looking at replacing my XL-RD3 with is the X-RD8. Yes, it is only a 70mm brake on that unit, but its a rear wheel, the front will keep its 90mm drum hub. The idea is due to the X-RD8 1st gear is the 100% or 1:1 straight thru gear, with the following gears at +30%,+14%,+14%,+14%,+14%,+14%,+30%. For a gear range of 325% vs 133% for the 3 speed. That is a HUGE difference, and the "start" gear(1) is still a straight thru pass to maintain strength in the gear the highest torque would be applied during take offs or hills. So instead of starting in 2nd like now, I would be starting in 1st. Granted I will no longer have a "granny" gear for hills, but 1) this is a road bike/ cruiser. Not offroading on it, and 2) I will be swapping the current 13T rear cog for a 23T or 24T which will give me a considerable amount more of torque for those occasional hills. I rarely ever used 1st on the current set up, as 2nd was fine for the hills near me. I think the extra torque from the cog swap should off set any issues on the low end, but with HUGE gains on the high end. So those of you more knowledgeable than I on these hubs, or those who wouldnt mind doing the math(feeling lazy, but may just have to do it to see) that can give me some good input as to how the 2 setups would compare/ differ for me. My only concern is the new hub(X-RD8) in 1st even with a 24T cog would not be able to climb a decent hill. Again, I am not talking about taking it on any trails. This bike ONLY knows the pavement and maybe some sand. I ride this 60-80% of the time to work and back. There are not many BIG hills here in town, but I am close to Skyline Drive, VA. So hills and mountains are nearby. I would just like a little re-assuring before ordering and swapping all these parts out. Not to mention re-lacing the wheel. I think that is all the technical info on the 2 setups I have to give. Oh, this is all on a cruiser(see avitar/pic or my build page) that weighs aprox 90lbs, has 26"x3" tires on 65mm rims, and powered with the BBSHD at 52v(dual 50amp capable 12.5ah packs in parallel). I am also about to finalize the decision between the Ludi or Phaserunner, so the BBSHD will have more torque(Ludi) and quite possible spin faster(phaserunner) soon. So the low gear may be moot at that point as it will be 2500-3k watts.

[Retrorockit]

You might look at the new Shimano 5 speed E bike hub.
https://www.google.com/search?newwin...30.a2wDv6kDhLc
You would probably have to get one form Europe.
https://www.husqvarna-bicycles.com/e...modelYear=2019

[Retrorockit]

Sheldon Browns gear calculator does IGH hubs. Pick speed @ 90rpm for gear units unless you have another preference. Then tire size, and chain ring. You can try several rear cogs at once.
https://www.https://www.husqvarna-bi...gear-calc.html
I don't think the new 5 speed is in there yet. The new one is 1:1 first.
With 2500W you might want to stay with the SA 3 speed for strength.

[Rider]

Watts in the range you are stating (2500-3000) can rip apart IGH hubs built to pedal bicycle specifications. I wouldn’t apply more than 750 watts to any of the bicycle IGH hubs myself. Good luck.

[Defjr333]

Thank Retrorocket. That should be helpful. When I built my 1st ebike I went with a Nexus 3 spd IGH, my new one I went with Sturmey for the drum brake with 3 spd. I chose both of those because of the many write up and reviews of people pushing 1k+ through them without issue. From everything I can find, and have read, the single most important thing is to make sure your primary starting gear is a straight through design. The 3 spd version has 2nd as straight thru, the 8spd has 1st as straight thru. Neither of those units use pawls or dogs to engage that gear, only the other gears. It seems a lot of IGH failures are on MTBs as the amount of force a standing rider constantly climbing and descending add a LOT more force into the equation than a seated relaxed rider on a cruiser bike frame could ever add. Or the constant start stop of torque from the motor. So if there is no difference between the 2 units starting gear how can one be weaker than another? Am I missing something? Starting in the straight thru gear, then shifting as needed to maintain/ increase speed means the vast majority of torque will only occur at start, once the bike is moving, that should take most the stress of the gears when I do shift. I can totally see blowing up an IGH if one starts in too high a gear from a stop or on a hill. Please help me to understand anything I am not grasping. Thanks everyone for the input

[Defjr333]

Watched a ton of videos on S/A 3 spd IGH rebuilds. I now think my current IGH can be salvaged/ repaired much more cheaply than I thought. It appeared to have damage on some internal components. But after watching, rewatching, slow motion, and much zooming, It appears I may be able to just tear this one down and replace the Axle key(HSA295) and Indicator Mark 4(HSA316), for a grand total of $10! I really wish there was a way to change the gearing ratios of these IGHs. I would love this one, if it had a wider gear spacing and range. I guess the bike parts manufacturers still dont take ebikes into consideration and still focus on the human powered components. I would think the first company to release an IGH that only has 3 gears, but with a range of say 200-300 and beefy enough to handle ebike power, would sell out quickly right now. It cant be that hard for them, as they dont need to focus as much on weight. Just make it STRONG and BIG RANGE between gears. So, I will be ordering those 2 items along with a few other small bits that will make the rear a little more reliable. I am still debating the 5 and 8 spd IGHs with 70mm drums. But for 10 bucks, I cant see rebuilding an entire wheel and the cost of the hub. Fix whats there, and think a bit more on replacing it later. I have never taken one of these apart, and the exploded diagram is terrifying. But, Youtube videos have given me a better idea of what items actually need to be disassembled. Not nearly to the exploded diagram point. It seems I will only need to take it apart to a point, where I can replace the axle key, then reassemble. I did verify the hub unfortunately is in 3rd gear right now since the Indicator chain is not installed(broke off). So I cant exactly use it, and dont want it to take to long to repair. That is the main reason I decided to fix this hub and not rebuild the wheel with a new one. I can get those 2 small parts overnighted cheap.

[Rider]

If you can fix your current S-A 3spd I would. Another solid hub choice is the Sturmey-Archer Heavy Duty RX-RK5 disc brake hub with a gear ratio of 243%. 3rd gear is 1:1 if that matters to you. I find that the 1:1 gear on IGH hubs seem to have the least drag and are the best gear to be in for the majority of your riding (hard to achieve). The 3rd gear 1:1 in this hub works well for off-road use, as you can gear your ride to the 1:1 for most riding. On the street I tend to be in 5th all the time. Having your starting gear as 1:1 isn’t nearly important if you aren’t running mega watts through the hub off the line. Slow starts that build speed will save IGH hubs; as does slow shifts without power. On a BBS02B all you have to do is a little short back pedal to kill the motor, shift and start pedaling again. Also, this hub has 25% gear spacing which is almost double normal pedal IGH spacing and better suited to electric assist bikes. I actually prefer the even wider spacing of the 3-speeds at 33% & 36%.

As for one IGH being strong than the other. Each IGH has a its own design and gear reduction and/or enhancement. All those internal spinning parts make each hub somewhat unique. The thing to keep in mind is that all these IGH hubs are only “designed” for pedal power and some for pedal power with a heavy loaded bike. I don’t know of any IGH hubs that are specifically designed for electric assist or even more powerful high wattage throttle use.

As electric bikes become more popular maybe a company will step up and build an undestructable electric assist IGH with proper electric assist gear spacing. I don’t understand why the major manufacturers haven’t created a mid-drive with the transmission built into it. That is what I see coming down the road.

[Rider]

Oh, and Sturmey-Archer also makes the RXL-RD5 which is the same hub, but has a 90mm drum brake in place of the disc rotor mount. ;-)

[Defjr333]

Thnx Rider. I had done quite a bit of research before I went with this 3spd (XL-RD3) at the start of the build. When I was discussing strength, I was referring to the "primary" gear. Whichever one is the 100%/ 1:1/ straight through. However you wish to term it. In my research, I found that they are NOT all the same. Some IGH's use a riveted 2 piece axle, and are not nearly as strong. The 3 speeds ALL have 1 piece axle, which is why 3 spd IGHs are generally all you see companies recommend with anything over 750watts. There are some exceptions, but those come with their own downfalls, mainly in the $$$ category. I ordered the parts from SJScycles 2 days ago, and tracking shows delivery on weds. Parts were $7. For the axle key, indicator chain, and a new, larger cog. Delivery was $12 due to rush ship. So under $20 and it should be all fixed. I am however still thinking of swapping out this hub, just maybe not so quickly. I will have to do some more research, as I dont like the limited gear range. As for the RX-RK5 or RX-RD5 in my case(gotta keep the drum brakes....lovem), I do not see much benefit. While it adds 2 more gears over my 3 speed, the tiny jump in overall range is just not worth the time and $ to do. It would be the cost of the hub($120, plus spokes, and the time to re-lace the rim). All to go from 133% range to 243%! That means 23% over my top and bottom range. I rarely use my granny gear as it is, so the lowest is a waste, and the top gear, is not enough of an increase to warrant the work. But the RX-RD8 however has a HUGE range, AND they are all scaled up from the primary 1st gear(which is a solid axle, not riveted). So, if my XL-RD3 with a 13 tooth cog has no issues with hills/ torque with only using the lowest gear rarely, the RX-RD8 should do fine with a larger cog. It would increase the torque and climbing ability on the strongest gear, allowing me to shift up when needed for higher speeds. Doing the gears this way makes more sense to me. Granted, I still think these companies should pull their heads out of their a$$es and make a 3 speed IGH with the gear range of the 8 speed. Make them heavy as crap, and over built. And the Ebikers will still buy them left and right. It would be cool to know what % of bike part purchases now days are for ebikes vs non powered to gauge what kind of purchasing power our community has. If numbers back ebikers being a rising % or even the majority now, it would change some minds at these companies.

[tklop]

If you want potentially lots more gears, you can get this hub too: http://www.sturmey-archer.com/en/pro.../cs-rk3-silver

(also available in black).

Gives you three-speeds from the SA-3 IGH via your left-hand shifter, while your right-hand shifter will work for the cassette... Lots more gears--all the same strength.

One drawback with the regular SA-3, is that the sprockets have only three engaging tabs--same as the Nexus single-speed sprockets.

If you're using larger rear-sprockets, and you're putting a lot of power through them (like I do), the regular galvanized ones won't last that long. I've got at least a half-dozen that spun their engaging-tabs right off. I hang them up like snowflakes at Christmas time.

The cassette-version eliminates this issue--even if you only used one of the cassette's gears, you'd still have a stronger setup... And odds are--with a good chainline--that you could use at least a few of the cassette's gears--even with a Cyclone or the like.

Best of luck!

Tklop

[Defjr333]

Appreciate that Tklop. I had looked at those too, when picking parts at the beginning of the build. I just dont like the look. While it more than likely would do what I wanted, it would look like a bicycle. I am trying my hardest to keep it "clean". The cassetteless IGH's just look nice. IMO. If S/A were to make a "Uber wide range" 3 speed they would fly off the shelves. They supposedly have a "wide range" 3 spd, but I have not seen specs on it. They come in many of the 3 speed models, and the model # just ends with a "W". But from what I have heard, it is not a big difference from the standard 3 speed. I want a 3 speed IGH with gear 2 as straight through(1 piece axle), gear 1 at -60% and gear 3 at 60%. That seems like at nice setting. We, ebikers are not using gears to "maintain cadance speed". We use them more like an actual transmission, shifting to keep the MOTOR rpms at the proper speed, and to climb hills, or go faster once lower gear is maxed. So I will probably do the 8 speed IGH and always skip a gear to make it a 4 or 5 speed with my preferred gear ratio/ range.

[tklop]

"...[we] are not using gears to 'maintain cadence speed'. We use them more like an actual transmission, shifting to keep the motor RPMs at the proper speed..."

I totally agree. Generally speaking, I only use gears 1 and 2 of my SA3--even on my massively heavy bakfiets project.

But there are times, esp. when operating off-road, where some more "fine adjustment" might be very nice--allowing higher motor RPM and torque at lower vehicle speeds. If I had a "granny gear" and could run my Cyclone mid-drive at max-rpm--while rolling along at walking-speed, I'd like that.

So in spite of my predominantly 2-gear experience--I'm still planning to experiment with the cassette/IGH combi at some point. For the versatility, but also--as I mentioned--for the additional strength. Yet I think it'd only be for the bakfiets. I don't know if I'd bother with it for a regular bike-project either. Maybe it would depend on my goals...

I don't use all my gears on my city-bike conversion either. With the 750W TSDZ2, it has a 7-speed Nexus IGH--and I am constantly skipping over unused gears. I pretty-much start in 2nd, then skip to 4th or 5th, then skip to 7th. If I'm climbing a long grade, I sometimes put it in 6--it just seems kinder to everything. But I've found the lower-gears are mostly just for "breaking inertia" on my way up to full-speed.

I think it's all about our intended use--as to what sort of "transmission" we e-bikers choose. This is illustrated well by my two extremely different projects--one which I feel could use more gears, while the other has too many! Maybe a bicycle made for extreme off-roading/hill-climbing, or the like, might need more gears to match motor-speed to the prevailing conditions of grades, surfaces, and terrains... But that's not my situation (for now).

I agree too--the IGH install is tidier--and I also agree about that dream of a broad-range SA IGH... A 1:1 with a plus or minus 60% would be nice--very nice indeed!.

But in fairness, even if the SA3 is only 1:1 and either + or - 33%---even that can be effectively a pretty broad range, depending upon the ratio between your front and rear sprockets.

When you mentioned barely ever needing "granny" gear--had me thinking you could go for a larger front-sprocket, and get a lot more "top end" out of your IGH. Depending upon your choice of front and rear sprockets, you should be able to basically get your 1st gear around the ratio where your 2nd used to be--effectively bumping your 2nd-gear up to a really-good "cruising speed"--and then your 3rd can be your "overdrive"--for when you've got that tailwind, and you're in a massive hurry... That's roughly what I've done with the bakfiets--because as you menetioned, the SA3's "magic" 1:1 rato 2nd-gear, is indeed the most indestructable, so it made sense to set up my gearing to allow that to be the gear I do almost all my riding in.

Anyways...

Best of luck!

Tklop

[Retrorockit]

Surly makes some nice single speed cogs with wide derailer splines on them.
https://surlybikes.com/parts/cassette_cog
They say you can stack them up and shift them. They don't have an indexing spline so you can reverse them for wear or chainline.

[tklop]

Those are really gorgeous! That might be just the thing to pop onto my as-yet unbuilt CS-RK3! *Bookmarked*

Even running a single rear sprocket--with spacers to take up the rest--would be stronger than the standard 3-speed sprockets... Much stronger.

And going "single-speed" with that thing--would allow the world's straightest chainline!

I like their suggestion on the item-page to do a rudimentary multi-speed with say--three single-speed sprockets to choose from. Way cool ideas!
.
Thanks, @Retrorockit

All the best!

Tklop

[Rider]

I wonder if Surly or anyone else makes a 3spd shifter/derailleur setup that works with three stacked cassette single speed sprockets?

I’m in the no derailleur camp too (if possible), but I like the idea of additional range over and above the CS-RK3 when wanted/needed. Also the ability to use the CS-RK3 as designed, but with the option of three different gearing combinations built in is appealing.

[Retrorockit]

I'm also runnning a Surly 50T stainless steel front chainring. ( it's that cadence thing).

[Defjr333]

My front is a 48t

[Retrorockit]

I've run 48x11t top gear and for me at 65 years old and a BBSHD it wasn't enough top gear.I also run 175mm cranks out of habit. On a 26x 2.16" bike you kind of have to reach for a good top hear. I couldn't find any offset 50T rings. I tried a couple narrow wide 50T, but ended up with a Surly SS and a roller chainguide at the top. On a Sunrace 8 speed 11-40 casette. I don't use power in the bottom 2 gears where the chainline is bad. Just for riding around pedestrians. The top 6 gears work great for urban ,and road work. I have another bike that's 750W TSDZ2 PAS with 44x19t Nexus 8 for guests. That's why I follow the IGH threads.

[Defjr333]

Parts are in, and hope to get everything done tomorrow. Replace axle key and indicator chain. Replace rear cog with 24T. Install new chain(s) with a half link(should help). Replace headlight relay(last one rated 10amps, new one is 30). Prime, paint, polish, replace front and rear fenders. Test everything, aka......."Go for a ride". There is one last thing I want to tackle tomorrow. For a "hint" see picture.