Ebiker33
Well-Known Member
Interesting, if you have rode both bikes which is more comfortable for hard packed/groomed trails ?
Woohoo.. we are live with the exclusive new controller for bafang ultra.. and more goodies!
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pushkar
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Ebiker33
Well-Known Member
If Pushkar can put Gates/Rohloff/Fenders & Rack on this he will have a very unique Ebike in the industry, the lightest one that's is for sure, and the ultimate hybrid.
I like that it also comes with the slightly beefier 3" tires.
The reviews on this bike from even people that own many Ebikes is fantastic, there is a guy who owns 6 high end Ebikes, he says it's the very best of the bunch.
German video of it
I like that it also comes with the slightly beefier 3" tires.
The reviews on this bike from even people that own many Ebikes is fantastic, there is a guy who owns 6 high end Ebikes, he says it's the very best of the bunch.
German video of it
pushkar
Well-Known Member
Rohloff and fenders are absolutely doable. Belt for that level of rear travel is definitely a problem.
Ebiker33
Well-Known Member
This is how the R & M Superdelite does it. However they are working off an aluminium frame.
pushkar
Well-Known Member
You are right that R&M is doing it. There are a couple others that are as well.
Here is my understanding of why this is hard on the Bafang ultra in particular.
With a smaller motor, like with R&M, we can be in the 35lb-50lb range, and not breach belt tension ceiling. So R&M full suspension will work because it is a smaller motor.
There are 2 ways of making this happen on the ultra.
Here is my understanding of why this is hard on the Bafang ultra in particular.
- Gates updated tension requirements here - https://www.gatescarbondrive.com/~/...arbon-drive-tension-recommendations.pdf?la=en
- Using the Bafang ultra with that much torque puts us in the "Punching rough pedaling style" category. (We tension our belts at ~43lbs as a reference)
- With FS and belt, we need to be atleast at 45lbs nominal (sitting down on the bike) position to account for belt slack. The drive train will routinely blow through the highest recommended tension with the incredible rear suspension travel.
- If we choose to have a lower tension to begin with, we risk the belt falling off and will need a belt guide and other contraptions.
With a smaller motor, like with R&M, we can be in the 35lb-50lb range, and not breach belt tension ceiling. So R&M full suspension will work because it is a smaller motor.
There are 2 ways of making this happen on the ultra.
- Have a smaller travel for the rear suspension.
- Have a soft tail suspension (another way of limiting travel with rear suspension).
smorgasbord
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It appears Pushkar is on top of the requirements.
For the curious, from Gates' eBike Integration Guide, which doesn't cover the Bafang Ultra: "Gates Carbon Drive components have been designed and tested to handle higher loads than most eBike motors produce. If you are using a mid-drive motor that exceeds 90 Nm of torque, contact Gates Carbon Drive to ensure system warranty."
As Pushkar points out, supporting both high torque AND big rear suspension travel is a tall order.
But, having recently ridden both a Gates/Enivolo hardtail with Kinekt seatpost and a full suspension carbon frame with SRAM 10-50 12-speed, I definitely preferred the ride of the full suspension, even on pavement. That may be due to the hardtail being quite 12 lbs or so heavier. My view is that the Kinekt definitely helps cushion the ride, but full-suspension helps the bike stay more firmly planted on the ground, even on pavement (which is often not totally smooth).
For the curious, from Gates' eBike Integration Guide, which doesn't cover the Bafang Ultra: "Gates Carbon Drive components have been designed and tested to handle higher loads than most eBike motors produce. If you are using a mid-drive motor that exceeds 90 Nm of torque, contact Gates Carbon Drive to ensure system warranty."
As Pushkar points out, supporting both high torque AND big rear suspension travel is a tall order.
But, having recently ridden both a Gates/Enivolo hardtail with Kinekt seatpost and a full suspension carbon frame with SRAM 10-50 12-speed, I definitely preferred the ride of the full suspension, even on pavement. That may be due to the hardtail being quite 12 lbs or so heavier. My view is that the Kinekt definitely helps cushion the ride, but full-suspension helps the bike stay more firmly planted on the ground, even on pavement (which is often not totally smooth).
pushkar
Well-Known Member
I want to stick with Gates just because of wider availability. I believe continental already withdrew their belt solution. I have not seen Bridgestone but will check it out.
Yes we are at the higher belt tension with Bafang Ultra. This is based on the recommendations we received as part of the certification.
I will look at the other designs and circle back. Thanks for the details.
Yes we are at the higher belt tension with Bafang Ultra. This is based on the recommendations we received as part of the certification.
I will look at the other designs and circle back. Thanks for the details.
Explorer-1
Have bike, will travel
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As I understand it, different designs of the tensioner (or dual tensioners) allow for more teeth on the sprocket(s) to be engaged with the belt and thus allow for a reduced belt tension, which can make the design easier. Not to say there are still not challenges. Also we don't really need that full power on the bike, so there is probably a very happy middle ground that can be achieved even if it means running both rear suspension and seat post suspension, It really depends on what the bike is being made for, or to what extremes is it expected to experience. If designing for 1% or even 5% of riders you can make your challenges a lot harder.
pushkar
Well-Known Member
1. Continental stopped producing belts and wound down that group last year.
2. I reached out to Bridgestone. Not a lot of active effort in furthering the ecosystem. Very limited range of sprockets - none for some of the hubs we need.
3. Goodyear - cant find the right contact.
The regular bikes you described work because the pivot point is the BB itself. IN such cases we wont need tensioner at all (may probably need a snubber to keep the belt in place). The Bafang ultra has a pivot offset of between ~95-125mm (depending on manufacturer).
I will keep looking. Thanks for the ideas.
So are you saying you need higher tension from the tensioner if you were to go Bafang Ultra?
I'm not an engineer so I may have missed something.
BELT TENSIONER:
Let's say you have two pulleys, one on wheel and one of crank (or whatever power source) and maybe think about pulling something heavy like cars.
The tension will stay on the top part of belt, not the bottom part.
Unless you use the tensioner on top part of the belt to push down the belt, I don't know if you need to add much tension on the tensioner?
For example, without tensioner, the bottom part of belt will be floppy and may come off, but all tensioner has to do is to keep the belt in place.
It's not like motorcycle where you use downshifting (in this case, all the tension comes to the bottom part of belt).
In addition, bicycle's cadence is only like 100rpm or so... it's not like motorcycle revving up to 14,000rpm.
Because motorcycle tensioners need to push down the belt pretty hard, otherwise the belt will come off because of centrifugal force.
However, I don't know if bicycle belts are exposed to much g-force at 100rpm (centrifugal force in this case)
I know simple rpm calculation doesn't say much, because bicycle chain rings and motorcycle sprockets have different sizes and all that, but I still don't know if bicycle belts will expand to outside due to centrifugal force like how motorcycles do on the dyno at full rev.
SUSPENSION TRAVEL:
You said that belt drive will be hard because of the rear suspension travel.
Both of your proposed solutions were to reduce the suspension travel.
Do you think the suspension travel (the travel of, the center of rear wheel) was the problem? or is it the distance from chain ring to rear wheel?
For example, what would be more problematic? 1) rear suspension with 50mm travel, but has 10mm change in rear stay, or 2) 140mm travel with 5mm change in rear stay?
The change in rearstay length will depend on the suspension geometry.
For example, I've seen a several MTBs with no change in chainstay length.
Gary Fisher
Klein
Schwinn
Now, even if you look at more modern MTBs, some of them clearly have more change in chainstays travel than other.
Depending on the design / geometry of suspension, the travel of chainstays differ drastically.
Lol, three of the worst riding fs mtbs of all time......
You can always pivot around the BB like Lenz does.
Ebiker33
Well-Known Member
Can you swing that with a carbon fiber frame?Rohloff Gates Full Suspension SVC Strato
care to elaborate? why are they the worst of three all the time?
What about Trek?
You're hitting home runs with all the URT bikes. The Trek Y bike was famously known as the "Why???" bike among my friends who owned them in the day, or commonly, as "The bike that kept trying to kill me". Here's the short answer, the suspension only really worked when seated, not when standing and descending at speed, when you definitely want it to. Plus, "The dark side of Klein's Mantra was, to some extent, the downfall of the URT concept as a whole. The two features that gave the Mantra its extraordinary pedaling performance: its high swingarm pivot location and biased bottom bracket position, interfered with its descending and braking performance and often at the worst possible moments. When descending out of the saddle and hard on the front brake, the rider's mass would push the cranks towards the front wheel, extending the shock, shortening the wheelbase and effectively steepening the bike's head tube angle. None of those traits are helpful while negotiating a technical downhill. All of them at the same time are just plain scary. " https://www.pinkbike.com/news/the-short-turbulent-life-of-urt-suspension-mtb-history.html
Lenz does make an ebike, it mounts the motor above the BB pivot. https://lenzsport.com/mountain-bikes/interceptor-e-bike/
Explorer-1
Have bike, will travel
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Love the SVO Strato Rally, if I ever want to buy a non-electric bike again, I hope they still make that one.
Re your belts, they are used as drivers for alternators, water pumps, and cams as most of you know. On a race car V8 that will turn 1000's of rpm, I ran them slightly loose as expansion of things when hot would not damage the belt, but tear up other things. On an oil pump drive, a belt guide was used on the crank pulley, the pump would be 'open' so the belt could be slipped off, this was a wider belt than you use and aligned pretty well with the pulleys and would not come off on it's own. The alternator and water pump used guides on both pulleys and the belts were the width you are using or thinner.
The only time a belt slipped was when it was set too loose on the oil pump, it chattered every once in a while but never damaged the belt, and tensioners were never used on any of them btw.
I would think it would take minimal amount of tension to keep the belt from skipping using my experience, but your application is different of course.
You might want to talk to these guys and tell them what you are doing, they will have experience that might apply to your application and they are good to work with. They also make parts.
The only time a belt slipped was when it was set too loose on the oil pump, it chattered every once in a while but never damaged the belt, and tensioners were never used on any of them btw.
I would think it would take minimal amount of tension to keep the belt from skipping using my experience, but your application is different of course.
You might want to talk to these guys and tell them what you are doing, they will have experience that might apply to your application and they are good to work with. They also make parts.
pushkar
Well-Known Member
58 lbs for size large.
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