Belt types

what is the diffrence between gt2 and htd belts

In general GT2 was an improvement over HTD. For robotics purposes it does not matter as the belts are hardly used at their limits. The HTD has a little less friction and the GT2 can take more torque being everything being equal. But you are not talking big differences. GT3 is a very slight improvement over the GT2 same tooth profile and pulley but very slightly higher torque rating

You can lift up to 275 lb with a properly tightened HTD-5 belt So its ok to use it on a climber to lift 1 robot. The limiting factor is less the belt ripping as you pulling teeth at a higher load

5 Likes

Does htd or gt2 stretch

If you order from one of the major FRC suppliers (or pretty much any other supplier), then the belts will be fiber reinforced and they won’t stretch unless you break them.

1 Like

we will buy from wcp so I guess they will be good thanks

And it’s probably obvious, but don’t forget that your belts and pulleys have to match each other, whatever you choose!

Added:

Actually, you can lift quite a bit more if your belt pulley/sheave is larger than your winch drum, or you have other reductions between the belt and climber.

1 Like

IDK According to gates at low rpm < 100rpm you will loose teeth at 275 lb and the Kevlar reenforced ones are guaranteed to not rip up to 300 lb. So it might be wise not to exceed those specs

1 Like

The HTD belts sold by FRC supplier are 5mm pitch and the GT2 belts sold by FRC suppliers are 3mm pitch. The difference in load capacity between these types of belts has more to do with the size class (5mm vs 3mm) than it does with HTD vs GT2.

It is common to see HTD 5mm belts used in higher load applications in FRC like the KOP drive base etc. In FRC GT2 3mm belts are mostly used for first stage reductions (higher speed, but lower torque/tension).

7 Likes

I’m certainly not advocating putting the belt under more than 275# of tension.

1 Like

and do you guys have any program for belt distance,making pulleys and tension

1 Like

Direct from your chosen provider, the WCP belt calculator.

2 Likes

is there any video that explaining it

The process is pretty self-explanatory.

Select 5mm for HTD or 3mm for GT2 in step 1. Keep the units in whatever you use for CAD.

Select the number of teeth on each of your pulleys in step 2. If you don’t have pulleys picked out, use the built-in ratio calculator to figure out what sort of speed reduction you want, then look on the website for available pulleys and get as close as possible to that ratio.

Step 3 is just a guess at about how far apart your two pulleys need to be, so the calculator can determine what lengths of belt would get close to where you need it.

The extra center option is used for tensioning. A positive extra center moves the pulleys farther apart, which puts the belt under more tension and vice versa.

Step 4 gives you the center distance for a belt of a given length/tooth count. This is the dimension you would include in CAD, not the dimension you put in step 3. You can pick from any of the three dimensions that step 4 gives you, but make sure to check for interference between pulleys or other elements once you have everything in CAD.

what is the diffrence between long or short belt what it means

The long belt is the size of belt sold by WCP that is one size above the belt that closest matches your desired center-center distance. The short belt is one size below. The long belt is given in case you find that you have an interference at the desired size and need to move up a size. The short belt is given in case you find that you have plenty of open space at your desired center-center distance and want to move everything closer together.

thanks i will use it

If you use Onshape, you can also use my FeatureScript belt calculator to make your belt runs directly. Pick the points you’d like to belt between, define your pulley sizes, choose your belt type and belt supplier, and my FeatureScript will automatically find the closest belt size and tell you what the proper belt center to center distance should be. You can also add 3D printable pulleys.

2 Likes

how much should i give the extra center what does it changes

With belts, I recommend NOT adding or subtracting, because they’re pretty stable.

For inexpensive gears (e.g. vex and AndyMark), add two or three thousandths of an inch.
With precision gears, I understand the answer is zero (but I haven’t worked with them outside of COTS applications).

For chain, be prepared for “stretch”. (The chain doesn’t really stretch, but as the rollers wear in, the chain does become longer.) I usually design for no extra, but with capacity to tension the chain either by moving one axle or adding a tension sprocket.

is it bugged or something I am entering 15t for first pulley and 60t for second pulley and i give 100mm for distance and it says that I need 6350 thoot belt