|
|
|
![]() |
|
|||||||
|
||||||||
![]() |
|
|
Thread Tools |
Rating:
|
Display Modes |
|
|
|
#1
|
||||
|
||||
|
Re: pic: Another Belt-In-Tube Drivetrain
Quote:
SDP/SI does sell 23t 5mm HTD pulley stock, however. |
|
#2
|
||||
|
||||
|
Re: pic: Another Belt-In-Tube Drivetrain
Quote:
|
|
#3
|
||||
|
||||
|
Re: pic: Another Belt-In-Tube Drivetrain
Quote:
For the correct belt thickness I made my belt drawings using the tooth heights and overall thicknesses of the belts given in the gates belt design manuals. |
|
#4
|
|||
|
|||
|
Re: pic: Another Belt-In-Tube Drivetrain
Hopefully not de-railing the conversation, but if anyone could humor me and take this discussion up a level, or link the relevant threads if it has been adequately discussed before, I'd certainly appreciate it.
#1: What are the pro/con of going to belt in tube if you are currently running chain in tube? #2: Do you believe the differences are significant? And why? As a data point, since I've been on 3005: In 2014 we ran a WCD style 3.25" 6WD tank with internal 9mmxHTD5x20T pulleys (Vex) on the inside of the robot. Never had any ratcheting issues (or would expect). Used VexPro/WCP bearing blocks (without retention cams) and had enough slippage issues (block vs. tube, our fault) to cause pulley misalignment and the press-on walls of the pulleys to come off. In 2015, we ran a chain in tube for an H drive configuration in 1x3x.125" extrusion, #25 chain, ~22-25T sprockets as I recall, geared at maybe ~10ft/sec. No issues to note. In 2016, we ran a chain in tube, 8WD with #35 chain, 8" pneumatic tires, in a 2x3x.125" extrusion. No real issues to note. Looking forward, though we may play around with "other" drive train options, it is highly likely we will prefer to similar drivetrain styles. We have the manufacturing capability to handle most designs (lathe, cnc mill, Al welding, etc), it just requires the investment of resources to create in the offseason and prove out. We value robustness over maneuverability, and think we can make up for any loss of mobility with extra driver practice in most games. What advantages might we be missing out on by continuing to run chain in tube? The things I can think of: - We have run 3" high tubing two years in a row, to accommodate extra center drop as well as a slightly larger sprocket to reduce chain loads/sprocket wear/etc. I have justified this in my head by saying the extra profile yields a stronger frame (torsional), but is it needlessly stronger? Would running belts make it easier to go to 2" profile and maintain the high safety factor I would like, even at large diameter wheels? - Are belts (when properly tensioned) more accurate with less slop when it comes to measuring distance traveled (for auton)? Or is the difference to chain not worth mentioning? - Is the system more efficient? More robust? Overall lighter (I know the belts are, but the hubs look heavier than an equivalent plate sprocket). - Other? Any rate, we will probably do another iteration of our drivetrain before build season next year, and the discussions on the belt in tube have me intrigued. Thanks for any input! |
|
#5
|
||||
|
||||
|
Re: pic: Another Belt-In-Tube Drivetrain
Chain is a bit less efficient than belts. Look up Team 234's paper on Chain vs. Belt, it has some good info in it.
Because both chain and belt are positive interference/have engaging teeth, neither is more accurate in auton. Timing belts might give you better performance by a couple hundreths of an inch, but that's about it. Belts are lighter than chain, but you're right that the pulleys are not. In my experience the weight difference is negligible. If you're considering switching drivetrains, running 9mm belts on 36 tooth pulleys or something could be a good swap for you. If you're already using 3" tall tubing, using the largest pulley (around 36 tooth) would net you a good factor of safety. I'm only going off the "24 tooth 9mm" being the absolute dangerous bare minimum for belts, so doing your own testing in the offseason would be a good idea. Personally, I prefer chain in tube for the compact factor and the strength that it offers; I've never broken a #25 chain (well I did once, but not in a drivetrain, and certainly not in a normal application). But if you're already used to designing with 3" tall tubing, maybe large pulley belts are the way to go for you. 2x2" tubing, or a setup like the one in this thread, are also options you can pursue. The low noise of belts is also a big appeal factor for me personally. |
|
#6
|
||||
|
||||
|
Re: pic: Another Belt-In-Tube Drivetrain
Quote:
|
![]() |
| Thread Tools | |
| Display Modes | Rate This Thread |
|
|