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[smithy]

Contact Gates & ask?
https://www.gatesaustralia.com.au/

I'm not sure Gates make toothed pulleys, only smooth idler pulleys & belts I believe....but I stand corrected.

Smithy.

[smithy]

All good thoughts guys....and you've all given me plenty of food for thought....Looks like i'll be doing a lot of thinking.

@Demoni, the welding of the Experia sprocket centre, (which is also the same as the Aprilia Tuono), to a matching pulley to get the required offset sounds like a good idea. I did the measurement of the rear pulley and although it will be very close, it should fit in the swingarm space if I get the offset correct, it's essentially the same overall diameter as the stock 52 tooth sprocket, which has ~10mm clearance.

Did a little field work for ya. Looks if you lined everything up perfectly there is 24mm between face of the motor and the inner face of the swingarm. Meaning you should be able to squeeze a 20mm bolt and pulleys in there.

Also you can download 3d files of every part Mcmaster sells. If you have a 3d printer you can import that into a slicer and print prototype parts.

Wow...thank you for that.....and yes, I do have 3D printers...two normal filament printers and a resin printer.

What bike is that by the way..?? Doesn't look like an Experia..??

Smithy.

[Specter]

maybe whats left of my ego heh.

Aaron

[Grauteufel]

I'm not sure Gates make toothed pulleys, only smooth idler pulleys & belts I believe....but I stand corrected.

Smithy.
[/quote]

Gates absolutely offer quite a number of toothed pulleys (and can even be swindled into prototyping for aspiring manufacturers.....)

[Demoni]

Wow...thank you for that.....and yes, I do have 3D printers...two normal filament printers and a resin printer.

What bike is that by the way..?? Doesn't look like an Experia..??

Smithy.

Your printers will be super handy in confirming part fitment and what modifications need to be made to the base parts. Easier and cheaper to squirt out some plastic before dropping $$ on parts. I also have a FDM and a resin printer, they are invaluable tools.
Yea their 3d files are super handy. If you have fusion 360 or another CAD program you can import the 3D files and modify them. Let me know if you need assistance with any turning, I have a PM-1130V and would be happy to assist.

That photo is of a EGO modified to accept an Experia swingarm. Little side project I'm working on in my spare time. I'll make a post about it once it's complete. The pulley is for another project...

[smithy]

Your printers will be super handy in confirming part fitment and what modifications need to be made to the base parts. Easier and cheaper to squirt out some plastic before dropping $$ on parts. I also have a FDM and a resin printer, they are invaluable tools.
Yea their 3d files are super handy. If you have fusion 360 or another CAD program you can import the 3D files and modify them. Let me know if you need assistance with any turning, I have a PM-1130V and would be happy to assist.

That photo is of a EGO modified to accept an Experia swingarm. Little side project I'm working on in my spare time. I'll make a post about it once it's complete. The pulley is for another project...

Great information Sir...thank you..!

I might take you up on the machining offer...although I do have a small metal working lathe at home in the shed.

Smithy.

[Biff]

The smaller rear sprocket on the Expria compared to the Zero will result in higher force in the belt for the same wheel torque.  I suspect, as other have, that the 20mm wide belt will not offer great durability with that increased force, but I suspect it will be able to handle the full torque but won't last very long. If you design your system to utilize as large of sprockets as you can reasonably fit, that will minimize the force in the belt and will probably be your best chance at making something that will last a while.

Also, I have some experience cutting belts to different widths, and it is actually quite easy and works just fine. Just setup a small jig that holds a sharp blade rigid and has a guide to keep the belt width accurate and pull it through.  Gates belts are actually manufactured in really wide sections and cut down to the desired width.

Here are some things to note:
The current Zero belt is 11mm pitch, which for a given width can handle more force than an 8mm pitch belt.
Zero used a 14mm wide 8mm pitch belt on their 2014 SR (144 Nm torque I think) and had a 30t front sprocket and 132T rear sprocket.
Zero changed to a 17mm wide 11mm pitch belt in 2018
Zero introduced a 20mm wide 11mm pitch belt with the SR/F in 2020
Zero introduced a 25mm wide 11mm pitch belt with the DSR/X in 2023

So you can see the general trend there to make the belt system stronger.  The 20mm wide 8mm pitch belt you are thinking of using should have about 50% more force capability than the 14mm wide 8mm pitch belt that Zero used on a production vehicle had. If you design your system to use around 130t wheel sprocket (the same as the Zero used, and is about as big as you can fit next to a motorcycle wheel), you should be able to handle about 200Nm of torque at the front sprocket.  I am not sure what the Experia gear ratio is but it is lower than the Zero, so your font sprocket will have to be larger than what was used on the Zero Motor to maintain the same gear ratio as the stock Experia . That will significantly improve the belt system's durability, but it might be hard to fit, so you might have to go with a smaller wheel and motor sprocket to fit.

-ryan

[Specter]

smaller pulleys /  etc are also going to require more tension to keep the belt from slipping in them, that puts more pressure / stress on bearings which over time could shorten their life.  just something to think about.

aaron

[smithy]

The smaller rear sprocket on the Expria compared to the Zero will result in higher force in the belt for the same wheel torque.  I suspect, as other have, that the 20mm wide belt will not offer great durability with that increased force, but I suspect it will be able to handle the full torque but won't last very long. If you design your system to utilize as large of sprockets as you can reasonably fit, that will minimize the force in the belt and will probably be your best chance at making something that will last a while.

Also, I have some experience cutting belts to different widths, and it is actually quite easy and works just fine. Just setup a small jig that holds a sharp blade rigid and has a guide to keep the belt width accurate and pull it through.  Gates belts are actually manufactured in really wide sections and cut down to the desired width.

Here are some things to note:
The current Zero belt is 11mm pitch, which for a given width can handle more force than an 8mm pitch belt.
Zero used a 14mm wide 8mm pitch belt on their 2014 SR (144 Nm torque I think) and had a 30t front sprocket and 132T rear sprocket.
Zero changed to a 17mm wide 11mm pitch belt in 2018
Zero introduced a 20mm wide 11mm pitch belt with the SR/F in 2020
Zero introduced a 25mm wide 11mm pitch belt with the DSR/X in 2023

So you can see the general trend there to make the belt system stronger.  The 20mm wide 8mm pitch belt you are thinking of using should have about 50% more force capability than the 14mm wide 8mm pitch belt that Zero used on a production vehicle had. If you design your system to use around 130t wheel sprocket (the same as the Zero used, and is about as big as you can fit next to a motorcycle wheel), you should be able to handle about 200Nm of torque at the front sprocket.  I am not sure what the Experia gear ratio is but it is lower than the Zero, so your font sprocket will have to be larger than what was used on the Zero Motor to maintain the same gear ratio as the stock Experia . That will significantly improve the belt system's durability, but it might be hard to fit, so you might have to go with a smaller wheel and motor sprocket to fit.

-ryan

Thanks Ryan....lots good info there...I've also been looking at an 11mm pitch belt system as used on the BMW F800 GT....The rear pulley is 80 teeth and just a little bigger in diameter than the Experia rear sprocket and I can use a cut down Experia rear sprocket to hold it...the front however is 40 teeth so only a 2:1 ratio...There is a Kawasaki EN440 which also uses an 11mm pitch system and a 25tooth front pulley, I can also get a belt from the BMW which is the correct tooth count, 182....might be worth investigating.

[princec]

Been thinking about this ... I can't quite see how the size of the rear pulley affects the force on the belt. The force is converted to a simple linear tension force by the front pulley, and this reaches the rear pulley the same no matter how big it is. The load is then spread out over the edges of all of the teeth on the rear pulley until it exits at the bottom. The only factor affecting the force experienced at the rear is the size of the front.

Cas

[Biff]

Been thinking about this ... I can't quite see how the size of the rear pulley affects the force on the belt. The force is converted to a simple linear tension force by the front pulley, and this reaches the rear pulley the same no matter how big it is. The load is then spread out over the edges of all of the teeth on the rear pulley until it exits at the bottom. The only factor affecting the force experienced at the rear is the size of the front.

Cas

You are right, the size of the rear sprocket on its own doesn't contribute to the force in the belt (at least not from motor torque), however if the system is designed to have about the same ratio as the original gearing, when you make the rear sprocket larger, the front sprocket gets larger too to maintain the same ratio.  And since the peak motor torque will be the same regardless of the sprocket size, the larger front sprocket will impart less force into the belt that a small sprocket, therefore under that assumption, a larger rear sprocket will result in less force in the belt. Example if the motor does 100Nm a sprocket with 50mm radius will result in 2000N in the belt (100Nm / 0.050m = 2000N), if you reduce the front sprocket size to 40mm radius (also adjusting the rear sprocket to be smaller to maintain the same front:rear ratio)  the force goes up to 2500N in the belt when the motor is delivering 100Nm.

That said, the same math is true for when the rear wheel imparts force into the belt through its sprocket, a larger wheel sprocket will impart less force into the belt when the wheel tries to accelerate the motor.  This is easiest to visualize by picturing what happens when the wheel lifts into the air while on throttle. In the air, the wheel will accelerate quite quickly as there is no longer any force from the road preventing the wheel acceleration, then when the wheel hits the ground again the tire's surface speed could be much faster than the ground speed, and the force of the wheel contacting the ground could be high resulting in excellent traction to slow that wheel back down to ground speed very quickly and as the wheel slows down it will create a force in the belt to slow the motor down too. That, combined with the motor probably still delivering forward torque from throttle demand results is a significant shock load and force to the belt.  Also, when the swingarm goes through its travel the belt will also cause the motor to rotate, typically that doesn't cause much motion (the amount of rotation will be approximately equal to the rotation of the swingarm around its pivot), and the nature of the physics around that motion (mainly due to suspension) tends to restrict the motor acceleration caused by suspension travel, so it is generally not a belt design consideration.

-ryan

[Grauteufel]

More power!

[Specter]

question is bullshit off the top.
you will never gain power.... just lose less.

in theory the belt should do better, it weighs less, less articulation so should lose less, however longevity plays into it as well.  how well does it handle shock, and extreme forces and overloads on it,  oh yah  ... pop!!  belts don't handle abuse as well as a chain does.

[ESokoloff]

question is bullshit off the top.
you will never gain power.... just lose less.

in theory the belt should do better, it weighs less, less articulation so should lose less, however longevity plays into it as well.  how well does it handle shock, and extreme forces and overloads on it,  oh yah  ... pop!!  belts don't handle abuse as well as a chain does.

Uhh?
The belt GAINED approximately 1 additional HP @ the rear wheel over the chain.
I question your claim that the belt “should do better” due to “less articulation”.
The belt has less then half the mass & flexes vrs pivots links imparting energy loss due to friction.
Regarding longevity… my last belt lasted 31.5k miles.
My 1st belt, not so much (too much initial fun).
Belts don’t do dirt/mud will tho (don’t ask how I know).

[Specter]

the belt can not GAIN any power, it does not produce power, only the engine does that.  the belt just transmits the power to the wheel, therefore it didn't gain it just lost less of the power the engine created.  You might say it preserved power, there is no GAIN, just less loss.

Aaron