3220 - Matt's Single Stage - Belt Drive Solutions? (ASAP)

[MitchJi]

Hi,

I'm in on the . 3220 group purchase. I'd really like to resolve this ASAP so that if possible I can plan on higher reduction and switch my order to a motor with a higher kv.

I plan to use Matt's single stage reduction and strongly prefer a belt drive. These are Matt's comments:

As for belt drive, my 3220 setups have all run chain drive. The twin 3220 setups are belted together using 26 tooth pulleys that have 13 teeth, each pulley, contacting the belt. That belt is also run very tight. For a 3220 on my reduction, I highly recommend a #25 pitch chain. That small pitch does not make much noise and they last quite a long time (not as long as a belt, though). The PK Ripper and the trikes have many hundreds of miles on them without wearing out.

So 13 teeth of contact with HTD 5mm pitch 15mm wide belt and high tension works. Matt said he would sell a single stage unit with the dual motor plate. This will allow the motor to be mounted 3.5" further (7" instead of 3.5"?) from the driven shaft for better wrap on the small pulley.

PLAN A: 30t/90t. 3:1 reduction and I think about 12 teeth in contact. ( this calculator doesn't go up to 90t HTD so I'm not sure).

Then I read this reference to GT2:
http://www.gates.com/brochure.cfm?brochure=7916&location_id=11539

PowerGrip® GT®2 belts offer industry leading performance over other rubber synchronous belts, at little additional cost.
# Twice the HP capacity as HTD®, GT and competitive RPP® belts, allowing smaller, more compact drive designs
# Largest selection of belts and sprockets in the industry

Reduced Vibration, Less Noise, Greater Accuracy
* Gates unique curvilinear tooth profile delivers smooth, quiet operation and precise registration

Tooth/Groove Contact Comparison
PowerGrip GT2 Belt---------HTD Belt------------Timing Belt:

Full contact between the PowerGrip GT2 belt tooth and sprocket groove improves resistance to ratcheting and backlash.

Twice the HP capacity and its smoother and quieter? Larger selection of belts and sprockets?

PLAN B: 20t/80t Power Grip GT2. If twice the HP is accurate this should work with the shorter face plate. If not I could always either use a longer face plate as is or trim it down and locate slots for something like 2" longer shaft separation. Custom pulleys are not prohibitively expensive so even if this requires custom pulleys that would be ok. 4:1 would be excellent (higher kv - more power and efficiency). Worst case 24t/92t?

Any reason this won't work? Will it be difficult or impossible to source belts (with the option of trimming the longer face plate I should have a pretty wide range of workable belt lengths).

Thanks!

Mitch

 

[Miles]

You could play with the Gates calculator, Mitch: http://www.gates.com/designflex/index.cfm?location_id=809 - though it's not particularly helpful for us... Use a service factor of 1

 

[RWP]

My recollection is that these belts have more power handling capacity at higher rpm's but at low rpm, like at starting out and low speeds, the power handling capacity of all 5mm belts is quite low and I think the 3220 will destroy any 5mm belt at lower rpm almost immediately. Check out the power curve/rpm charts at SDP.
You can increase the 5mm power handling by going to wider belts but the pulleys have to be custom made from pulley stock. Doubling the belt width doubles the power handling capacity.

Going to 8mm would solve this issue completely, but 8mm is an increase in size and not nearly as available as the 5mm stuff.

Hope this helps and good luck.

 

[recumpence]

My findings with the various GT series belts and Powergrip are that there is not nearly the torque capacitly difference between GT and GT2 Powergrip as they claim.

Basically, I am really trying to save you the hassle I went through on the second stage of my recumbent drive. I tries everythign to stay with a belt rather than a chain. In the end, I had to bend to what I knew would work------------ A chain.

You can go with a larger pitch (8mm). But, the pulley choices are not nearly as good, and the pulleys are huge. In the end, the 5mm pitch, 15mm wide belt is really the only option without getting very custom. The best you could do is go with that setup and an amp limiter and make sure you limit the amp draw to keep the belt from skipping.

I think it is kind of a losing battle trying to run a belt at a 3220's potential with any reasonably compact size to fit a bicycle.

Matt

 

[MitchJi]

Hi Miles,

You could play with the Gates calculator, Mitch: http://www.gates.com/designflex/index.cfm?location_id=809 - though it's not particularly helpful for us... Use a service factor of 1

I tried with three browsers (Firefox, Camino, and Safari) and I still can't get in. Would you please pm me a copy?

You can increase the 5mm power handling by going to wider belts but the pulleys have to be custom made from pulley stock. Doubling the belt width doubles the power handling capacity.

Thanks. Matt explained to me that there is a big efficiency hit with wider belts.

Basically, I am really trying to save you the hassle I went through on the second stage of my recumbent drive.…

The best you could do is go with that setup and an amp limiter and make sure you limit the amp draw to keep the belt from skipping.…

I think it is kind of a losing battle trying to run a belt at a 3220's potential with any reasonably compact size to fit a bicycle.

I really appreciate all of your help and advice. With a Trike I have more space available. You posted the following on another thread:

My recumbent primary stage uses a HDT 5mm pitch 15mm wide belt and can handle 7kw at
6,000 rpm. That is with a 22 tooth motor pulley (10 teeth engaged) run very tight

With moderate belt tension, 5kw is fine.

I used the Calculator at sdp-si.com. I had to use half sizes, figure out the angle differences for shaft distance and double the results because the calculator only goes up to 72t in 5mm pulleys. This means that I could not try odd sizes of pulleys and the meshed teeth jump from 10t to 12t. I got the following which should be very close:

Ratio   Pulley Sizes Meshed  Shaft
                     Teeth  Separation 
   4:1     28t/112t    10t    (about 7") 
   4:1     30t/120t    10t    (about  6")
   3.7:1   30t/112t    12t    (about 7.3")

So at 4:1 I can get 10 or 11 teeth meshed using up to a 120 driven pulley. And at 3.7:1 I can get 11 or 12 teeth meshed. I was planning on 3:1 so 3.7:1 or 4:1 means I could use a 5 turn instead of a 7 turn.

Do you think if I get 11t or 12t meshing it can handle somewhere between 5kw and 7kw comfortably? Care to pick a number?

Do you think using GT2 make any difference as compared to HTD (even 10% or 20% might help a lot)?

If Gates is exaggerating on the power handling they might also be exaggerating on the noise but this might be an advantage:


Thanks!

Mitch

 

[spinningmagnets]

If 5mm-pitch gives you the off-the-shelf pulley diameters and belt choices you need, consider using two parallel belts. Just a thought...