Chain drive vs. cogged belt drive(timing belts)

[Donut]

Were you a high traction pushing robot? If so then you might want to go with #35 chain.

Our team has used #25 chain every year except 2004 and haven't had problems breaking them that I've ever known of (I know we haven't the past 2 years; don't know about before). We've never been a robot with high traction wheels that does a bunch of pushing either though, so I doubt we put as much stress on them as other teams do.

[colin340]

we have used them for the past 3 years
2004 the arm that hooked the bar- worked well
2005 the arm for picking up tetras- we use timing belts on the secant pivot but when we put it together and tryed to move it with no load and it riped the cogs off so we change 35# chain
2006 the upper Harv that moved balls to the shooter we used double sided timing belt

but after seeing 1503's robot i like chain

[Dick Linn]

We've used #35 chain for 5 years. We have never had a drivetrain malfunction and only need to adjust chain tension once during a regional. That is probably because we don't get much practice time in ahead of time and things are just getting seated

One thing I like about chain is that it's easy to add or remove links to get the right length. When we can do it, we position the gearbox between the front and rear drive wheels (4 wheel drive). This keeps the chains short, which helps with weight and reduces the effect of chain wear. Chain tensioning is done by placing shims (washers) under the gearbox where it mounts to the frame. Very simple, very sturdy.

[Kingofl337]

We used cogged belts on mech wheels last year and we broken normal timing belts and stripped Kevlar ones.

We ended up using gears for reliable operation. We also tried chain but couldn't find a robust 8 tooth sprocket the fit the dewalts.

[RyanN]

Originally Posted by LordBritten

Mt team used #25 chain last year and our chains would break all of the time. that is why lost in the semi-finals at the Portland regional we did not have time to fix the chain.

If you design the drive train correctly, you should never have any problems. (use large sprockets, dont have any slack, have chain guides)

We have been a high traction robot for two years with our 6WD system. The secret is the larger sprockets, it allows for more chain to go over a single sprocket than a smaller sprocket, which would give you more torque. Think of it as a bicycle, if you put your bike on the highest speed, it causes you to push harder (which also puts more tension on the chain), if you put it on a low speed, there isn't as much tension on the chain. The same applies with using 2 large sprockets or 2 small sprockets. The weight cost to go to larger sprockets is minimal, and will save you at competition.

[Sean Schuff]

Our team (93) used cog belts and cogs for our drive train last year and found that the drawbacks outweigh the benefits - at least for our application. We had a four-wheel tank-style drive using one CIM on each side and our modified variation of Andy Baker's two-speed transmission. We ran into three major issues with the belts.

First, the belts needed to be aligned precisely and captured enough that they don't wander side to side at all. Any wander will result in the belts walking off and the loss of one or both sides of the drive. Wander is also an issue with chain (although much more forgiving) but seemed amplified with the belt.

Second, the belts had to be extremely tight or they would skip over the teeth in the cog and not transfer any motion to the wheels. To remedy this meant to tighten the belts with a tensioner which led to our third problem.

Finally, the belts had to be tightened so much to prevent slippage that we created a ton of friction in the system which definitely translated to loss from the CIMs to the floor.

This year we are returning to chain and sprockets. It has worked well in the past and we know it will work well in the future. We've used #35 in the past but are going to test out #25 to save weight. Based on what many on these forums have to say, the smaller chain should be sufficient.

Our adventure into belt drive was definitely a learning experience and we would return to them if we could overcome some of the problems we encountered. At this point it is easier to return to the familiar and focus on improving that. If anyone has ideas on how to overcome these "opportunities", please share your insights!

Good luck!

Sean

[Andrew Schuetze]

Chaning the thread a bit,

How many teams have used vee belt for their drive-train. Percieved advantages from someone considering using it this year; less weight than rollerchain, make your length as with chain via hot-knife butt welding kit, alignment less of an issue than with timing belt as vee groved pulley helps center, some slippage not an issue, no need to tension as it stretches to fit.

I am ordering Eagle brand orange 85 and clear 95 vee belt for the drive-train and the same durometers in one size of round belt for ....

I've been told that teams from Michigan have been using this stuff for years

APS

[ewankoff]

although we did not use a v belt for drive it was again on our shooter. the v belt performed better than we thought and showed no signs of slippage and no damage short of normal ware and tare. the v belt and its pully's were the only component on our robot that did not need to be fixed at all.

from my experience, a v belt is easier to align/tention/is more forgiving than a cog belt.

[Gdeaver]

In 2003 we used 4L v belts for the drive. They worked OK but since then we have gone back to #35 chain. V belts will slip when torque goes above a certain threshold. This can be a good thing. Locking up a drive is bad. Something has to give or the motors are going to fail. We used timing belts for our arm in 2004 and 2005. If we have to use an arm again we will probably try something different. Timing belts probably would have been good as a drive for the shooter wheel this year. We used direct drive for the shooter and chose the wheel to match our velocity requirements. Less points of failure and eliminates some friction losses. The timing belt pulleys of the size needed for 6 wheel drive are expensive compared to IFI's aluminum sprockets.

[RTTComanche17]

Chain!!! #35. We have used it with no diffuculties whatsoever. It ran our drivetrain last year. We ran an extremely high ammount of torque through them and they never failed. We ran at 2.5 feet per second with 4 2" wide 8" diameter IFI drive wheels with the wedgetop tread material. We never met anyone we couldn't push, at regionals or at Nationals. We bent our frame, which pinched the chian between the wheel and the frame causing it to rub and misalign. Never fell off and never broke. Can a belt do that?!