pic: Belt Drive Chassis Take 2

[Big Ideas]

The TENSION required to transmit the driving force will be a function of degrees of wrap around the cog not the number of teeth engaged. This is because driving force creates a force that lifts the belt away from the cog. It will take less belt tension to transmit a given force for a single segment wrapped twice as far then the 2 segments shown. This is assuming the tooth phasing problem mentioned above is solved. One more note. I have never seen this configuration used or recommended. It is a clever thought, but likely wont yield the hoped for result.

When you evaluate variations like this always look at the forces generated and if EXTRA structure has to be added to deal with those forces.

[Jared Russell]

Originally Posted by Hawiian Cadder

as long as the belt has an even number of teeth, and the distance between the center to the two outer pulleys is exactly equal, the teeth will line up on top and bottom.

oh, and the number of teeth on the center pully must also be even

I believe that this holds only as long as the center pulley has an even number of teeth.

[Hawiian Cadder]

Originally Posted by Jared341

I believe that this holds only as long as the center pulley has an even number of teeth.

that was in the edit, i realized that moments after submitting the reply.

[Chris Fultz]

Originally Posted by Sh1ine

Were you happy withe the 9mm wide belts? I have been thinking about going to the 15mm wide 5mm pitch belt, but they are huge.

Have you looked at the loading on your drive, to know what size belt you need? The Gates site has several design tools to help you with the evaluation. You might be surprised at the capability of the 9mm belts.

Also, is there a reason that you don't want to use two belts, instead of a single belt? It is a much simpler design, but I don't know what design constraints you are working with. Just curious.

[Chris is me]

The main constraint is that the team wants to keep the belts inside the AL tube - right now it's sized at 3x1.5 inches I think? I'm pretty sure it can be done with a 9mm belt.

[Sh1ine]

Originally Posted by Chris Fultz

Have you looked at the loading on your drive, to know what size belt you need? The Gates site has several design tools to help you with the evaluation. You might be surprised at the capability of the 9mm belts.

Also, is there a reason that you don't want to use two belts, instead of a single belt? It is a much simpler design, but I don't know what design constraints you are working with. Just curious.

There really is no reason. I starting off thinking that it would be easier to have one belt, and get the system in the tube. Now after reading everyones thoughts I think it is going to be harder. Did you have a spring tensioner in your system? Did you use steel pulleys or were you able to find Aluminum one? I can only find GT2 steel pulleys.

[AustinSchuh]

Originally Posted by Sh1ine

Did you use steel pulleys or were you able to find Aluminum one? I can only find GT2 steel pulleys.

From a quick search on SDP-SI.com, I'm finding the following 9mm wide GT2 5mm timing belt pulley in Aluminum. FYI. There are plenty more like it.

A 6A55-032DF0916

[Sh1ine]

Originally Posted by Sh1ine

There really is no reason. I starting off thinking that it would be easier to have one belt, and get the system in the tube. Now after reading everyones thoughts I think it is going to be harder. Did you have a spring tensioner in your system? Did you use steel pulleys or were you able to find Aluminum one? I can only find GT2 steel pulleys.

I was just reading the thread on your bot, and learned about your tensioner. Very ingenuous. Did you end up using a similar design for the game? How did the belts hold up over time?

[artdutra04]

Originally Posted by Sh1ine

There really is no reason. I starting off thinking that it would be easier to have one belt, and get the system in the tube. Now after reading everyones thoughts I think it is going to be harder. Did you have a spring tensioner in your system? Did you use steel pulleys or were you able to find Aluminum one? I can only find GT2 steel pulleys.

SDP-SI sells lightweight sprockets for 5mm HTD timing belts that have a polycarbonate body and various styles of aluminum hubs. We used the 'Aluminum T-Insert' sprockets at the time (which we broached keyways into), but might consider Fairloc hubs for the future. Both of the mechanisms (the shooter and ball intake rollers) were high-speed, low(ish)-torque systems, so the lower torque capacity of HTD belts versus GT2 wasn't an issue. We didn't have any issues with the belts (or pretty much anything else) on our robot that year.

[TroyCDH]

Reading this thread and a few other threads on the chain/belt compairison I see few spots where people talk of belts breaking, slipping or loss of the belts teeth/lugs. I don't understand. Maybe the small pitch belts from the Kit-of-parts would slip. Buy a better belt. Thinking of a car's timing belt or serpentine belt there is no way I would expect to see a failure in some belt like that on our robots.

I have also seen comments about robots pushing against each other and the chain one always wins over the belt. Saying the belt slipped. Here again if the correct belt is used and tensioned correctly etc I see no way that the contact patch between the wheels and carpeted floor could outlast a good belt.

I guess the real question is what type of belt is required for drive wheels?

Thanks--good luck to all in 2011

[Clem1640]

tres cool.

I'd suggest spring loading both of the chain tensioners equally. This should help the belt alignment issue on the middle wheel.

Putting this drive inside a rectangular tube is neat and will protect it. It will also make maintenance a bear.

I'd suggest prototyping after getting the design down. Look at maintenance ease an reliability in the prototype. Try to break it.

Good luck.

[apalrd]

Originally Posted by Clem1640

Try to break it.

Don't just drive it around. Run it full speed over a bump and see if it survives on impact. Run it full speed into a solid object (e.g. not a freshmen, a wall works well) and see if you can break it. Keep it stalled against a wall to see if it breaks before the breakers trip (if properly designed, the wheels should slip and the belt should not. If neither slips, the breakers will trip after a few seconds. The belt should not slip ever). Try pushing some other robots around. Fight well.

Do this for a really really long time (at least a few batteries). Then you will know if it is good enough.

You might be surprised how much abuse it has to take.

[Aren_Hill]

That's a 2"x1.5" tube Chris

[Crawler]

im going insane trying to figure out where i can get that tensioner, or even what its called, if that is the one for the belts that Gates gives us then please send a product number or something
Thanks