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... I want to end up with a belt like a gates Poly Chain GT.
You said that I should have this engineered, any suggestions on finding an appropriate one?
The Gates Poly Chain GT Carbon Belt Drive Systems manual has just about everything you need to know about using these belts.

If you plan carefully (so your shaft spacing is right for the specific pulleys and belt that you choose) you don't need much adjustment, but you do need some to account for imperfect construction, belt stretch, and ease of installation.
 

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Brian is right about the shaft spacing related to belt and sprockets tooth count. But in that pesky real world again, even if you have fixed on an ideal ratio with a chain drive, you may not find a combination of acceptable belt and sprockets tooth counts that allows the set up to work with your limited belt tension adjustment. In case this happens, you should have another backup plan for using an idler. I haven't had to use one yet. But I would think it should be a fixed(rather than spring loaded) one that could handle the heavy belt tension during regenerative braking.
 

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... in that pesky real world again, even if you have fixed on an ideal ratio with a chain drive, you may not find a combination of acceptable belt and sprockets tooth counts that allows the set up to work with your limited belt tension adjustment. In case this happens, you should have another backup plan for using an idler.
Absolutely - the manual helps with selection, but there are only a finite number of available combinations.

I haven't had to use one yet. But I would think it should be a fixed(rather than spring loaded) one that could handle the heavy belt tension during regenerative braking.
I agree - these belts don't stretch much, so an idler (or adjustable drive or driven component) should be rigidly clamped in place after tension adjustment, to work in both regenerative braking and driving in reverse.
 

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Discussion Starter · #25 ·
My thought in the original design was that the motor sprocket would be my way of getting the belt on. I re-drew diagram with the double overhung with 2 pillow-block bearings in front, as you suggested. I have preselected some drive belt solutions to give me the center distance measurement. I attached my current choice.
 

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I guess this would make putting on and taking off the belt easier. Although, I don't see it. My suggestion is to mount the two closely spaced bearings, supporting the drive shaft sprocket shaft, on the other side of the sprocket. This leaves space in front of the sprocket to pull the belt through. It looks like my design would have to have the motor mounting flange or plate removable (bolted-in, like the motor) to gain access to the drive shaft sprocket. Or, you may be able to cut a large enough opening in the plate to pass the sprocket through.

On your drive design report I see the install/take-up range distance is only 1.41" instead of the 1 .5", I estimated. My bad. The 25 tooth drive sprocket is near the lower end of the tooth count you want to use to minimize noise and belt wear. Just a few more teeth on this sprocket would reduce the noise and possibly let you use a narrower, cheaper belt and sprockets. Also notice the force pulling on the shafts is ~600lbs. This info will be useful to determine the bearing loads.

What does ~1950 RPM on the drive shaft translate into vehicle speed?
 

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Discussion Starter · #27 ·
I will need 2500 rpm on the driven sprocket 5000 on driver motor sprocket to reach 50mph
thanks for the link to the gates manual. In the manual as well as in using the design software they seem to limit rpm to 4000 rpm and in other places in the manual it indicates 5000 rpm. Perusing the manual. It looks like I could use a larger driver sprocket with a workable center distance.
On flopping the bearings to the other side the only way to create enough space would be to keep moving the motor plate forward to allow space to pass sprocket and bushing over end of shaft. On that subject, I could not find any info on the overall width of sprocket assembled with bushing. Does the bushing nest in to the sprocket?
The chain sprockets that I already purchased slip on and gates sprocket would be taper lock. It doesn’t seem too hard to thread the shaft through the bearings and sprocket. Am I missing something? And thank you both for your responses.
 

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I will need 2500 rpm on the driven sprocket 5000 on driver motor sprocket to reach 50mph
thanks for the link to the gates manual. In the manual as well as in using the design software they seem to limit rpm to 4000 rpm and in other places in the manual it indicates 5000 rpm. Perusing the manual. It looks like I could use a larger driver sprocket with a workable center distance.
My impression from the manual is that the charts and tables cut off at the high speed end to avoid violating a 6500 ft/min linear belt speed, but if you calculate specific combinations - or find them in the software - you can get combinations at moderately higher shaft speeds which stay within that 6500 ft/min limit. Bigger sprockets are better (to reduced belt tension required and to bend the belt less), but a potential problem with enlarging sprocket diameter is increasing linear belt speed to an excessive level.
 

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AIR the 6500 ft/min limit is a max for regular cast iron sprockets as the Gates manual states on page 102:

"Centrifugal forces developed beyond this speed may prohibit the use of stock gray
cast iron sprockets. For rim speeds above 6,500 feet per minute, contact
Gates Power Transmission Product Application for other alternatives."

The sprockets are sometimes made of other materials. Sintered steel, ductile iron, stainless steel come to mind. These sprockets usually have higher rim speed and RPM limits. Unfortunately, these limits are not listed in the catalog, that I've been able to find. The RPM limits are printed or embossed on the sprockets themselves. So, you'll have to do some looking and hunting or contact Gates or a supplier.
 

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Discussion Starter · #30 ·
Doesn’t appear that I would be anywhere close to 6500. More like 4500 rpm. Any thoughts on assembled width of sprocket and bushing?
 

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On flopping the bearings to the other side the only way to create enough space would be to keep moving the motor plate forward to allow space to pass sprocket and bushing over end of shaft.
To get around this, you could make the motor mounting plate removable, as I mentioned before, to get good access to the sprocket and bearings. So instead of welding the plate directly in place to the motorcycle frame, weld in some mounting points on the frame that the plate bolts to.

The chain sprockets that I already purchased slip on and gates sprocket would be taper lock. It doesn’t seem too hard to thread the shaft through the bearings and sprocket. Am I missing something?
As I mentioned before, in the real world, rust, grime and metal burrs(like from set screws) can make it very difficult to remove bearings and sprockets from a shaft.Taperlock type bushings are usually an exception to this problem. This could make a normally simple belt change a very difficult, drawn out process. With a removable motor mounting plate, as described above, you would only need ~1/2" clearance in front of the drive shaft sprocket to twist and slide in a new belt. This could be done without moving or removing the motor plate, sprocket, shaft, or bearings.
 

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Doesn’t appear that I would be anywhere close to 6500. More like 4500 rpm. Any thoughts on assembled width of sprocket and bushing?
Sprocket rim speed is different from RPM. Calculate the rim speed the same way you calculate the vehicle speed from the RPM and diameter of the rear tire. Just calculate it in feet per minute, instead of miles per hour.
 

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AIR the 6500 ft/min limit is a max for regular cast iron sprockets as the Gates manual states on page 102:

"Centrifugal forces developed beyond this speed may prohibit the use of stock gray
cast iron sprockets. For rim speeds above 6,500 feet per minute, contact
Gates Power Transmission Product Application for other alternatives."

The sprockets are sometimes made of other materials. Sintered steel, ductile iron, stainless steel come to mind. These sprockets usually have higher rim speed and RPM limits. Unfortunately, these limits are not listed in the catalog, that I've been able to find. The RPM limits are printed or embossed on the sprockets themselves. So, you'll have to do some looking and hunting or contact Gates or a supplier.
Good catch. (y):)

When I found the belt speed limit it wasn't in context with that note, and I didn't search the rest of the catalog for the explanation... apparently I should have.

It didn't make sense to me at first because centripetal acceleration isn't just related to speed (if using tangential speed, it's the speed squared over the radius), but it looks like the pulley is approximated as a ring with the centre just locating against side force and taking torque, so the hoop stress in the ring is proportional to tangential speed squared, independent of radius (because it's proportional to the product of the squares of angular velocity and radius, and tangential speed is the product of angular velocity and radius). Convenient! I had incorrectly assumed that the limitation was the belt, not the pulley.

While it technically makes sense, I was surprised by this limitation... in automotive applications 5,000 RPM is routine and shaft speed typically isn't an issue for pulleys, most of which are cheap and simple stamped steel. Of course for a toothed belt the pulley can't be stamped, and cast iron is dense (increasing the hoop stress). A suitable grade of aluminum is the obvious solution.
 

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Doesn’t appear that I would be anywhere close to 6500. More like 4500 rpm.
Sprocket rim speed is different from RPM. Calculate the rim speed the same way you calculate the vehicle speed from the RPM and diameter of the rear tire. Just calculate it in feet per minute, instead of miles per hour.
Right - 6500 ft/min, not 6500 RPM.
 

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Discussion Starter · #35 ·
Here is a revised plan. I am going to see if one of the jack shaft bearings will fit between original motor plate and the elastic coupler.
This will achieve clearance to change belts. I am also seeing if I can mount motor with slotted mount holes so the motor can move up and down for adjustment. It is 115 lbs so tough to move.
 

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You'll be much happier with this set-up. You should keep the clearance between the front of the drive shaft sprocket and the motor mounting plate to a minimum, just enough to slide the belt through. This will keep the motor sprocket as close as possible to the motor output shaft bearing, reducing the load on it (minimum overhang load). If you opt for this design, you'll have to make the motor mounting plate removable or make sure there is an opening in the plate large enough to slide the drive shaft sprocket through, and access its Taperlock bushing.

Belt velocity should be very close to the rim velocity. Formulas for calculating this are on page 110 of the manual. AIR the max rpm of this motor is moderately low, 6-8k rpm? You will probably be alright with the cast iron sprockets-but you should confirm you are below the max 6500 ft/min rim speed. I'm working with motors running 10-12k RPM, and having serious design issues trying to keep the sprockets below their RPM limits.

You can use the formulas on page 107 to calculate the bearing loads for your set-up. It's basic teeter totter/ lever arm stuff. Being so close together(you should try to make them as far apart as practical), the bearing and shaft loads will be quite high. This means the shaft diameter and bearing size will need to be larger than you might imagine. Bearing suppliers will rate their bearing load capacities based on the RPM. This is where a good contact at bearing store or an engineer will be very helpful. Don't forget, these large loads will be transferred to the mounting plates, their supports, and the motorcycle frame.

You can weld threaded clips (sometimes just regular nuts will do) to the mounting plate that use jacking screws to move the motor to tension the belt. Threaded rod sections welded to the motor mounting washers will work in a pulling type adjuster.

Unfortunately, some set-ups can be very noisy. It would be a good idea to have a plan to completely enclose the drive. This will also keep dirt and rocks out.
 

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You can use the formulas on page 107 to calculate the bearing loads for your set-up. It's basic teeter totter/ lever arm stuff. Being so close together(you should try to make them as far apart as practical), the bearing and shaft loads will be quite high.
I had the same thought. Could the bearing on the output shaft side be spaced further back (to the right in the drawing) from the mounting plate, or is the rubber coupling location fixed?
 

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Just to clarify, z-guy, you write that you have an AC30 motor? Is that the size motor that's no longer available? 115lbs? Isn't that the weight of AC50 motors?
 

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Just to clarify, z-guy, you write that you have an AC30 motor? Is that the size motor that's no longer available? 115lbs? Isn't that the weight of AC50 motors?
Wow, it looks like the HPGC AC-30 is from so long ago that HPEVS (Hi Performance Electric Vehicle Systems) was still called HPGC (Hi Performance Golf Carts) at the time. If it's this old HPGC/HPEVS motor, it was apparently (and this is more forum rumour than factual information) an earlier version of the AC-31, which became the AC-34/35. The AC-34/35 (which are the same size but wound differently) are the same diameter as the AC-50/51 (which are again, the same size but wound differently) and an inch shorter, and lighter as a result. The AC-3X weigh 85 pounds; the AC-5X are 115 pounds. My guess is that the AC-30 would match the current AC-3X external dimensions and weight.

Given the entirely unoriginal naming system, and the existence of other "ACnn" motors unrelated to HPGC/HPEVS, it could also be an entirely different motor... except that it looks like an HPEVS motor and HPEVS seems to have confirmed that.
 

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Discussion Starter · #40 ·
The rubber coupler is fixed without a lot of re-design there. To fit a bearing between the rubber coupler and the original motor plate, I will need to modify my cardon shaft slightly to allow the coupler to move back 1/4".

The motor is in fact an early AC-30 and I believe it's weight is 115 lbs. I bought this from Frodus and spoke with HPEVS about it before purchasing. Older formulation of metal in the windings or something, slightly less efficient than the newer ones.
Anybody know about the sprockets and hubs if they nest into each other? Tried to ask a distributor this question but got no response. This will tell me how much room I will need and how far forward to install new motor plate.
 
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