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]

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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