Pole Internal Gear Transmission /MGU Integration Thread

[slickrock]

Houston, we have a problem.

Today I have received the 122T belt. So far I have the following belts: 120T, 122T and 125T.

The problem I discovered is the chain growth:

• The 120T belt is too short. Nothing to add here.
• The 122T belt is slightly too long when the bike is unweighted. Yet it is too short when and no full wheel travel could be achieved.
• The 125T belt is too long when the bike is unweighted. It allows, however, the full wheel travel.

I suspect the chain growth is too great for the existing setup (Pinion BT1 chain tensioner, 39T front sprocket, 34T rear sprocket).

So far this is a bike stand-testing. Next week I will have my forks ready so once they are fitted, I will test the system with my own weight. I do not expect different results but I want to confirm it.

So, it is time for the collective brainstorming. What to do here? Any thought and/or suggestions?

So,

1. If you are planning to use a SpeedHub, then AFAIK, you can only use 19, 20, and 22 Tooth sprockets as those are the only available.
2. Minimum gear ratio for this hub is 1.90, so if you are using a 39T chainring, a 34T sprocket would be way below that and would break warranty. If you stick with the 39T chainring, then largest rear sprocket would be 20T. A 19T would probably provided a more suitable ratio since this is an EMTB.
3. If this ratio is still too low then you would need bigger front sprocket, like a 42T or 46T
4. The consequence of these changes is that the belt lengths available in the suitable range: 118T, 122T, 125T and 128T - one these combined with your choice of front chainrings and rear sprockets with your desired gear ratio, might get you a combinatorial belt deflection that gets you in the ballpark with your tensioner kinematics, while supporting the chain growth limits of the Voima. BTW, what is the chain growth of your Voima?

All of this is tediousness is the consequence of not having some form of horizontal adjustable dropout (which the Voima/Sonni do not) to fine tune the belt choice. As such, one can only resort to experimentation, as you are well on your way of doing. Great progress so far I might add.

 

[tooFATtoRIDE]

Hi all,

The progress is slow at the moment and will remain so for the next month or so. On the flipside, I think I have the tensioning roller positioned fairly well.

Protos 8 and 9 are of the same basic adapter shape but with the tensioning roller positioned is a slightly different spot. I think the final adapter extension should have 2, maybe 3 options tensioning roller position options, just in case I decide to play with the different rear sprocket sizes at some point in the future.

Belt tensioner prototype no. 8

www.youtube.com

Proto 9(1) is the same as Proto 9 but I added a white straight line to help visualize the exact movement of the roller vs the pivot point. I think it looks ok for a cardboard aided design.


Thoughts? Comments?

 

[slickrock]

Hi all,

The progress is slow at the moment and will remain so for the next month or so. On the flipside, I think I have the tensioning roller positioned fairly well.

Protos 8 and 9 are of the same basic adapter shape but with the tensioning roller positioned is a slightly different spot. I think the final adapter extension should have 2, maybe 3 options tensioning roller position options, just in case I decide to play with the different rear sprocket sizes at some point in the future.


Proto 9(1) is the same as Proto 9 but I added a white straight line to help visualize the exact movement of the roller vs the pivot point. I think it looks ok for a cardboard aided design.


Thoughts? Comments?

Impressive. It's good to keep the configuration options open as you will be forced to to move to a 19mm or 20mm rear sprocket if you go Rohloff with you existing front chainring and then choose the best tensioner configuration for that setup.
Feel a bit helpless on my side as I've yet to receive my Sonni.

 

[tooFATtoRIDE]

Feel a bit helpless on my side as I've yet to receive my Sonni.

When do you expect to receive your bike? What sort of setup do you plan for it? Are you more or less settled on it or is it all fluid situation?

 

[slickrock]

When do you expect to receive your bike? What sort of setup do you plan for it? Are you more or less settled on it or is it all fluid situation?

Most likely an additional month due to K1 bikes coming after k2 bikes. I ordered a mullet configuration (first for me), but I don't want to commit to it unless I try the setup with a rear 29 as well. So I expect to experiment with the bike outside of any geared transmission setup so I can properly review it and compare it to my Voima experience. For the future setup:

1. I'm definitely going with the Speedhub, so unlike the Kindernay, you definitely have to commit to a wheel size.
2. I want to use the Nicolai tensioner as I expect it will directly mount to Bosch motor, while taking advantage of the "naked" motor design of the Sonni.
3. Dropout mounted Snubber - still need to research which on to get. My current dual suspension MTB setup does not use one because my bike has zero chain growth (because of the concentric bottom bracket suspension) and also has adjustable dropouts
4. Rear Sprocket: originally wanted to go with largest rear 22T sprocket, as I want more teeth engaged in the rear to deal with higher torque situations with an EMTB setup.
5. Front Chainring: That said, my worry with a 22T rear I would need to get a 50T chainring to get a higher gear ratio better suit to EMTB. But chainring may be too large and this may squeeze the space chainring the upper swingarm, and besides may look a bit huge as folks come to expect 32 or 34 teeth on EMTB chain setups. At the other extreme I could go with a 19T rear matched to a 42T front or split the difference with a 20T rear / 46T front.
6. Belt - Well this depends chain growth, cog choices and tensioner kinematics. Like you I will have to experiment due to the lack of adjustable horizontal dropouts on the bike (unlike with the Nicolai).
7. E14 Electronic Shifting: Will definitely commit to this, but only after I can prove the above setup works. I've tried the E14 and was blown away by its performance.

 

[tooFATtoRIDE]

It is alive, sort of .... Still lots of work ahead of me.

 

[slickrock]

It is alive, sort of .... Still lots of work ahead of me.

This is absolutely fascinating!
I can see almost almost NO chain growth! Did you fully articulate the suspension in this video? I mean the tensioner is hardly doing any work at all - any less movement you could almost get away with a fixed tensioner. Do tell us what the actual chain growth is of your bike.

Also, what is you rear sprocket size? As mentioned in prior posts you will be limited to 3 sizes if you go Rohloff.

Overall, this is quite promising in belt-driving a Pole.

 

[tooFATtoRIDE]

Hi, I am glad there is at least interest in this prototyping stage

Indeed, there is very little chain growth. I guess the roller's placement is crucial. Around time when I started prototyping with various extension arms, I visited a pretty cool Swiss brand using Gates components. Once very interesting recommendation was to play with the exact position until there is very little tensioner arm movement. Two reasons were given: (1) it prolongs life of the entire sutup; and (2), more importantly, it ensures relatively constant belt tension.

What you see on this short video shows the entire suspension articulation. I have disconnected the shock to ensure there is enough of belt length even slightly outside the shock travel of 75mm.

What you see here is with the front sprocket size 39 and the rear sprocket size 32. I tested it with 34, though the roller was mounted in a slightly different spot. That is why the tensioner arm extension has 5 potential mounting options. I know that for the Rohloff setup there will be some additional testing required. At present time I do not have sprockets in the required size. I test it on a hub with Shimano HG freehub body yet Rohloff has its own mounting pattern. However, to counteract this, I have three different belt sizes available (120T, 122T and 125T) and 5 potential mounting options. I hope this would be enough to make it work.

Lastly, apologies for infrequent postings. I do not have access to a workshop or garage so major changes only happens when I visit my brother, who has basic equipment to make it work.

 

[tooFATtoRIDE]

Most likely an additional month due to K1 bikes coming after k2 bikes. I ordered a mullet configuration (first for me), but I don't want to commit to it unless I try the setup with a rear 29 as well. So I expect to experiment with the bike outside of any geared transmission setup so I can properly review it and compare it to my Voima experience. For the future setup:

1. I'm definitely going with the Speedhub, so unlike the Kindernay, you definitely have to commit to a wheel size.
2. I want to use the Nicolai tensioner as I expect it will directly mount to Bosch motor, while taking advantage of the "naked" motor design of the Sonni.
3. Dropout mounted Snubber - still need to research which on to get. My current dual suspension MTB setup does not use one because my bike has zero chain growth (because of the concentric bottom bracket suspension) and also has adjustable dropouts
4. Rear Sprocket: originally wanted to go with largest rear 22T sprocket, as I want more teeth engaged in the rear to deal with higher torque situations with an EMTB setup.
5. Front Chainring: That said, my worry with a 22T rear I would need to get a 50T chainring to get a higher gear ratio better suit to EMTB. But chainring may be too large and this may squeeze the space chainring the upper swingarm, and besides may look a bit huge as folks come to expect 32 or 34 teeth on EMTB chain setups. At the other extreme I could go with a 19T rear matched to a 42T front or split the difference with a 20T rear / 46T front.
6. Belt - Well this depends chain growth, cog choices and tensioner kinematics. Like you I will have to experiment due to the lack of adjustable horizontal dropouts on the bike (unlike with the Nicolai).
7. E14 Electronic Shifting: Will definitely commit to this, but only after I can prove the above setup works. I've tried the E14 and was blown away by its performance.

I was thinking about this. Based on the pictures and videos, given a different bottom suspension pivot location when compared to Voima, it appears that there might be less space for sprocket.

Perhaps you could inquire with Pole what is the absolute maximum front sprocket size that could be fitted. Of course, the number of teeth does not correspond directly between the belt and chain options. I am not sure what's the conversion formula but from what I heard for a reputable source, an 32T gates sprocket equals roughly to an 32t chain sprocket. Once you have info from Pole, perhaps with additional info on a max sprocket diameter, we could work out whether there would be any interference. I hope not, but let's work it out.

 

[tooFATtoRIDE]

Work in progress. Still plenty to do.

 

[Onetime]

View attachment 138170

View attachment 138171

Work in progress. Still plenty to do.

How’s the belt drive working out And how’s the gearing with it only being a single speed?

 

[tooFATtoRIDE]

How’s the belt drive working out And how’s the gearing with it only being a single speed?

The belt drive is awesome. I see no issues so far. I am having issues with the rear Mavic hub that came with the bike but nothing with the belt.

The current setup (39T front, 32T rear, 125T belt) is significantly undergeared for any fast riding but plays little role when gunning down the track. I have two other setups to test: (1) 39T front and 28T rear; and (2) 39T front and 24T rear. I have two additional belts lengths to test: 120T and 122T. I am not sure whether it is going to work but I will find out.

Btw way I took my Voima for a little bit of shake-down. It absolutely rips and scares the shit out of me most of the time. I have a 8 year gap in mountain riding so any moment it gains speed, and it does easily, I am on the brakes immediately. It rides very differently to my other bike (Nicolai ION GPI) so this is something that will take time to get used to.

One more thing I noticed is that the Pole's equivalent to anodizing is absolute shit. It is so weak that I am shocked. It feels like it gets scratched when I just look at it in anger. My Nicolai bike mentioned above it bulletproof. Pole's equivalent is a kindergarden play. Total disappointment.

 

[slickrock]

View attachment 138170

View attachment 138171

Work in progress. Still plenty to do.

It’s wonderful to finally see an actual belt drive setup on the Voima. I have to say your bike definitely looks the part out there in Switzerland and hints of a Pole MGU setup in the future.

You also probably have the only single-speed Voima out there. I agree that you should play with some more gear ratios to extract the best narrow gear range for your type of riding. As it is there a too many gears with typical MTB setups. For a while I was thinking of a limited IGH gear range to simplify and lighten things, such as the Classified Hub, but unfortunately at this time there is no Gates sprocket adapter available - belt drive is a must. Keep up the good work.

 

[tooFATtoRIDE]

Ohhh fuuuuuck

 

[Sander]

OK, I got a parts list from the Rohloff distributor in the U.S. that handles non-OEM E-14 bike integrations. On can feel goosed enough pricewise with just converting a bike to use a Rohloff hub, but adding electronic shifting adds to the sticker shock (R&M and Nicolai must get some heavy discounts it seems). it would make sense to first see if I can get the Sonni integrated first with belt drive tensioner and hub itself before committing to an E-14 setup. While I omitted the prices to the parts list below (you can PM me if interested), I'm curious if any of you know a European (not necessarily Euro) Rohloff retailer where one could get favorable prices for Rohloff parts (In my case for Yanks like me since the U.S Dollar is strong, and also can take advantage of VAT tax discounts ).

1. Rohloff Speedhub 32-hole A12 DB PM, black-8097PM-300268 [Thru-axle version of the hub need for the Pole. Technically this is not an E-14 specific part] Note: Rohloff 32-hole A12 DB PM, black-8097PM-(,8097PM,8097PM,,,,,)

2. Rohloff A12 PM Set (Art. #8558+8555) Axle-plate A12 PM + PM Bone*-8564-278430 [Technically this is not an E-14 part, rather it is needed to attach hub to rear post mount bikes that aren't built specifically for internal gear rear hubs. ] Note: Rohloff A12 PM Set (Art. #8558+8555) Axle-plate A12 PM + PM Bone*-8564-(,8564,8564,,,,,)

3. Rohloff E-14 DC/DC-CAN Converter-278418 [E-14 Specific part] Note: Rohloff E-14 DC/DC-CAN Converter-(,8802,8802,,,,,)

4. Rohloff E-14 Switch Unit (Shifter) 265834 [E-14 Specific part] Note: Rohloff E-14 Switch Unit (Shifter)-(,8801,8801,,,,,)

5. Rohloff E-14 DC/DC-Can Converter to Shifter Unit Cable 600 mm-8806- 299344 [E-14 Specific part] Note: Rohloff Rohloff E-14 DC/DC-Can Converter to Shifter Unit Cable 600 mm-8806-(,8810,8810,,,,,)

6. Rohloff E-14 Shifter Unit, E-Bike-278385 [E-14 Specific part] Note: Rohloff E-14 Shifter Unit, E-Bike-(,8803,8803,,,,,)

Hi Slickrock,
Since I'm grinding a couple of cassettes each year with my Voima, I'm also interested in a geared hub like Rohloff. But if you look at the exclusion criteria I think our dropouts are to thick...:-(

A-12 (142/148/177/197mm) - Rohloff AG

www.rohloff.de

 

[slickrock]

Hi Slickrock,
Since I'm grinding a couple of cassettes each year with my Voima, I'm also interested in a geared hub like Rohloff. But if you look at the exclusion criteria I think our dropouts are to thick...:-(

A-12 (142/148/177/197mm) - Rohloff AG

www.rohloff.de

Good eye.

Well damn if this is a firm requirement! The disc side swingarm on my Sonni is 22.5mm. I'm really hoping the problem is not on the inboard side where the hub goes (after all Boost 148 is a standard), but rather on the outboard side. If this is the case, I don't see why there would be a constraint in making a reduction sleeve extension along with a longer bolt. This would need to be custom machined if I can't make it work with the fitting kit. Still this is more added complexity/risk. I would need a firm answer from Rohloff as to why this 17.55mm constraint exists before anymore steps are taken.

I might just abandon Rohloff and go with the 3X3 NINE, as it is built under a true 12mm thru-axle design, can safely handle full power motors, and looks the have a standard 6-bolt rotor. I just need to convince them to let me purchase their electronic shifter to complete my OP design objective.

 

[tooFATtoRIDE]

...

I might just abandon Rohloff and go with the 3X3 NINE, as it is built under a true 12mm thru-axle design, can safely handle full power motors, and looks the have a standard 6-bolt rotor. I just need to convince them to let me purchase their electronic shifter to complete my OP design objective.

It is not a standard 6-bolt rotor but the brake rotors are available from a 3x3 dealer when ordering the hub.

 

[slickrock]

Ok, so it’s been awhile since I last contributed to this thread. The intervening time has been spent getting one of the very few Sonni’s up an running at the very moment Pole closed it’s doors (now, for good, at least as far as that business entity is concerned). Now that I’m comfortable with riding characteristics of the bike (and there’s a lot to share I’m sure when I write an eventual review of the bike) I’m returning the steps to get my bike into a belt-driven internally geared transmission. I hope this should prove interesting or useful despite that I’m working on a bike that nearly nobody else has. My sense is that a lot of this will transfer to other bikes and might be especially relevant to bikes with Bosch Gen 4 (perhaps Gen 5 as well) motor.

ASAIC, and I’ve mentioned this before, while belt-drive is not required to moving to a geared transmission, it is inextricably essential to having a geared transmission in the first place and there are too many benefits to belt transmission, not to mention a capability that is simply denied with derailleurs. So anything that gets in the way of incorporating a belt drive is simply a nonstarter.

Which gets me to the biggest obstacle of a belt drive solution for MTBs/EMTBs: the need for a spring tensioner, which does 2 important things that standard chains and derailleurs have done all along:

1. Since belts sizes can’t be adjusted like chains can, there has to be a mechanism to take up slack and maintain tension on the belt. This can be statically provided by a fixed tensioner or also the design of the bike itself. Take your typical single speed bike - it may have a horizontal dropout or a sliding vertical drop out that allows you to move the back the rear axle to take up belt slack to obviate the need of tensioner at all.
2. But unfortunately we have the problem introduced by dual suspension designs on MTBs/EMTBs: almost always the rear axle path of the rear suspension causes the chain length to grow as it progresses through the travel. It’s a dynamic problem that requires continuously varying spring tension on the belt. It’s interesting that suspension chain growth has never been an issue for suspension designers because the derailleur IS a spring tensioner - this critical gear shifting component is already there to take up the duty of taking up slack. But same cannot be said of IGH hubs, and so a spring tensioner is essential.

The other problem with spring tensioners (especially belt tensioners) is there is no standard by which they are designed, located, and implemented. Some of this has to do with the fact that internal geared transmissions are fairly rare to begin with mountain bikes and only a small batch of bike companies have MTB/EMTB dual suspension bikes expressly designed for geared transmissions. Those that do each have their own spring tensioner solutions, and admittedly some can be rather ungainly, intrusive, and heavy (when it comes to belts) or look too much like freaking derailleurs (when it comes to chains) - a clear aesthetic I want to be rid of in the first place.

But what of MTBs/EMTBs that were not designed for geared transmissions? Well there’s no choice but to either adapt an existing spring tensioner or craft your own. I’m in the former camp (I’m a software guy). But to adapt a spring tensioner requires that everything has to work: a firm mounting placement, the attachment, the space required, tension arm angle, etc. The best approach is to prototype solutions and choose the best one.

For the tensioner itself I chose the one made by Universal Transmissions, which is the tensioner used by Nicolai for the EBOXX and Saturn IHG/MGU bikes, and chose it for the following reasons:

1. This tensioner has a transverse mount design so it can be tucked behind the motor so as to not protrude under the bike where it would otherwise be prone to damage from undercarriage bashing and rock strikes. A counter example here is the Pinion tensioner, which is exposed and rides along the bottom of the motor where a bash guard would normally go.
2. The tensioner is not hard-designed for a particular frame, but rather is designed to swap out its mounting flanges. This design basically allows you to craft your own flanges to adapt the tensioner to your own bike.
3. The current flanges that come with tensioner are designed (or at least I thought so) to mount to Bosch Performance CX Gen 4 motors , which the Sonni, as well as many other esteemed bikes have.

That said there are two downsides to this tensioner:

One is that’s it's heavy. I’m not sure why, but the tension arm appears to be some kind of cast ferrous metal rather than CNC or forged alloy. A prior version had a tension arm made of CNC alloy but the flanges were an intrinsic part of the tensioner casing, reducing its adaptability. Still I feel this is the best tensioner out there for the job. Hopefully future versions will bring about a lighter design.

And the other problem was the time and effort just trying to get one. Universal Transmissions does not directly market this tensioner (at least a few months ago this was the case). Rather, they rely on B2B relationships with bike manufacturers to spec the tensioner for their bikes, unless of course you were willing to buy, say a hundred of them. That said, I did find an indirect way to get the tensioner and if you are interested you can PM me and I can describe what I did.

Regarding the installation, I had hopes to just bolt the thing onto the Bosch motor, since the flanges were designed for this motor and because the Sonni has basically a naked motor bolted to the bottom of the bike frame as it’s signature (notorious?) design aesthetic, seemingly offering easy open access to mount the tensioner. Unfortunately this was not case, as the rear mounting point surfaces of the frame bulge out (for added strength I suppose) and threw off what could have been clean and simple mounting point opportunities. As such I had to design my own flanges.

So for the adaptation design, I decided to go with a 1/8” 7075 alloy sheet, cutting it out (by hand or perhaps by laser) as a flange to be mounted to each side of the tensioner. For prototype purposes I used 1/8” ABS plastic sheet in place of the alloy sheet to try out and test various designs. Once I settle on a functional design, I’ll carve out the alloy versions, matching the shape of the plastic ones, which can be seen below.

I used various-sized ABS plastic spacers and longer stainless bolts to stand off the flanges from the inner mounting plates of the motor. This was tedious process of trial and error to the get the offsets right to get the tensioner aligned with the Gates front sprocket with a 52mm chainline. Note that I avoided using the bolt motor mounts that attached the frame to the motor. Instead, the longer bolts replaced the ones used to attach the smaller stock alloy plate mounts to the motor. I also temporarily installed a back plate that was used as a small jig to keep the tensioner alignment true when I drilled holes into the plastic flanges. This plate will be removed in the final product.

Overall I think it looks pretty clean and looks like it will work. Which is important because the next steps involve purchasing the the internal gear hub, shifter, and associated components, which is a financial commitment I didn’t want to make unless this critical spring tensioner solution was in place.