# Gearing friction losses with wheels chained together.

So I’ve been really liking the idea of chaining wheels together for flywheels, but haven’t had a chance yet to test everything empirically.

Mathematically though, which would be theoretically more efficient, gearing the motors up and then chaining them together, or gearing the motors up separately from the gearbox that combines the motor outputs?

I think you might want to keep the chains moving slower rather than faster. Gears lose energy to friction when their teeth microscopically slide over each other. Chains lose energy to friction as their various parts rub on the teeth of their sprockets and even the chain itself is pivoting everywhere at its own tiny hinge points. I think that because the chains have a lot more parts rubbing against each other, you will want to keep the amount of motion the chain makes to a minimum. But I must admit that’s just my opinion: I haven’t tested that theory and a true analysis of the situation would require having detailed knowledge of the gear tolerances, etc. So it’s just food for thought.

Connect motors then gear up if you are doing a multistage compound gearing. If just a single gear conversion (eg 1:7) then people usually connect the motors as they gear them. Is that what you are asking; it’s a little confusing? Basically just try to minimize the number of gears/sprockets and axles required

that’s the idea. if you connect the motors, and gear up twice (once for each flywheel), you actually have more gears in your system than if you connected them, geared up once, and then connected that to one side, and chain the two sides together. You have less gears in the system, but now you have chain moving rather quickly.

Oh, I think I understand now. Driving one flywheel as a slave off of the other may cause some problems with the velocities not matching. For example, when the flywheels launch a ball the slave wheel may slow down before the other wheel due to slack in the chain.
But I don’t know; it probably just depends on how well you can minimize friction. Powering each flywheel separately and chaining them together is perhaps ideal—aside from friction.

I remember reading in vexforums that chaining is more efficient, but I never really found many things which looked into the subject. Which, I guess *can *make sense.

Cause with chaining, the tension would be distributed equally throughout the surface so the force is quite perpendicular

On the other hand, you have to deal with the pressure angles of the gears. Due to the angled forces, not only is the force applied inefficient, but I would think that because force is applied the wrong way and into the gear, it creates frictional forces as well, killing itself.

I’ve also read in general applications that spur gearing is more efficient than belts or chain. On the contrary other shapes of gears are more inefficient (but you don’t need to worry about that cause you’re probably only going to use spur since beveled vex gearbox sound ridiculous).

Of course don’t kill yourself when it comes to chain. If you make your chain to tight, you are defeating your own advantage. If you make the chain too loose, then you’re falling victim to the chain itself.

Don’t take this to heart, but I’ve seen too many exceptional teams die at worlds because even though their design was theoretically amazing, it was simply too fragile or corner cutting that it couldn’t handle the brutality of competition or imprecision (62,1114, 148, 2425, 2915, 254, 44, etc.).

OK. I really shouldn’t have brought chaining into this, since the question applies without chains too. So much info and every answer so close to the question, but I guess that to get the right answer, you have to ask the right question, otherwise the answer is “42”.

Even if it WASNT chain, the question was focused around whether or not doing the split early in the gearing, or late was better. As in, which of these configurations is better. (a * indicates gearing)

1,) Flywheelstage2stage1motor clusteridlerstage1stage2flywheel
2,) motor cluster
stage1stage2flywheelidleridler*flywheel

One has more moving parts, but the other has more moving parts moving at high speed It doesn’t really matter if it’s chain or not (at least it didn’t to me until I saw the replies here.)

I love all of the other replies, not things I thought of really, like slack in the chain.

Just keep in mind that the motors “see” friction at the flywheel magnified by whatever gear ratio you have. So if there’s 0.05 inch-pounds of frictional torque at the flywheel, it might look like 1.25 to 1.75 inch-pounds to the motor. The more moving parts you have, especially closer to the flywheel end, then the more frictional torque will be “seen” by the motor.

Also keep in mind that a chain effectively puts a force on a sprocket axle that is unbalanced. The two force vectors of the chain coming and going around a sprocket (the two T2 vectors in the picture below) add up to a total of T1, which can equal as much as 2 times T2. This unbalanced force will increase the friction present on the axle bearing. (Note: it’s possible you might not see T1 = 2 (T2) when there is lots of slack in the chain but then you’ll have other frictional problems to worry about.) In any case, you will still end up with an unbalanced force on your axle.

EDIT: Sorry, the diagram I chose is misleading in that the resulting vector T1 would obviously point in the opposite direction to what’s shown, but think of T1 as being the force that the shaft would need to exert to overcome the combined forces of the two T2 vectors. :o

So I guess the bottom line is this: reduce all your friction as much as possible but especially keep friction-generating activity as close to the motor as you can.