H-Drive Issue

I created H-Drive but the middle wheel will spin. but wont make the robot strafe. For some reason .mp4 isnt allowed so i cant post a video of the issue

The wheel isn’t touching the ground enough, try adjusting vertical spacing on the drive base so it does touch the ground.


during next level our team had a suspension that pushed the wheel down. it use rubber bands. so maybe do something similar.


it is the same sized wheel on the excat same line so it is touching the ground

Well if the wheel spins but the robot doesn’t move as a result, then there muse be some difference in the height of the middle wheel compared to the other wheels. Otherwise the robot would move when the wheel spins.

Getting all the wheels to be at exactly the same height is one of the trickiest parts of building an h-drive. If the middle wheel is even a little bit higher, things won’t work too well. Even if the rollers still appear to be touching the ground, the middle wheel may still have less traction and may free-spin rather than moving the robot as a result. Getting that alignment perfect will be easier with IQ parts than in EDR because there is less slop in the connectors, but some care will still be required.

Another concern is the curvature of the thing you’re driving on. Almost no surface is completely flat, and if the ground is slightly lower under the middle wheel then you get the same set of problems.

These two issues are why a lot of good h-drives actually have the middle wheel hinged, and use rubber bands to push it into the ground to ensure good contact.

Some photos of your robot would be helpful in further diagnosing this issue.


Can you please dump the file into your Google drive and make it sharable by link?

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Obviously not enough lol . Move it down more

IQ fields are hard plastic, not squishy foam like VRC.

Still though it clearly does not have enough traction. This can be remedied by moving the wheel down. If moving it down more off centers the base, the robot is likely too heavy

just a technicality, but i believe a better explanation would be one that relates traction. it’s not the height that matters, it’s the how much traction the individual wheel has, compared to it’s acceleration; just because something has more normal force doesn’t mean it necessarily has more traction, cuz traction in newtonian is essentially Ff=μN. in fact in this case, it may not even have to do with the height (although it’s undoubtedly much more plausible), it could be the friction coefficient of the rollers themselves that’s lacking- yet either way, the main issue mr banjoman has is with traction


Well yeah that’s true, and a good point. But assuming that it’s the same type of wheel being used all around, and one of them isn’t significantly more worn than the others or something, I think it’s reasonable to assume the wheels have pretty similar coefficients of friction.


Just a few things to note that may or may not be useful:
-Yes, the field is hard plastic but if your field is on carpet (even the hard kind in schools) it can have a significant impact. We built a kind of lattice out of wood which helped a ton
-the overall weight of your robot does matter too but if your bot isn’t really heavy it shouldn’t matter much
-the balance could be an issue. even if your wheel is in the center, having all of the weight on one side will make the bot tip just enough
-linty wheels could be another thing. try wiping them with rubbing alcohol
-speed ratio could be too high resulting in not enough torque. anything above 2:1 has never worked for us
-the hole you’re using could already we worn down causing a bit of give
bonus tip: add a square lock plate (the kind with the square hole) to the inside of your wheels using two-standoffs to give them two points of contact with the shaft.

So basically, h-drives are stubborn little things. But I still love them. I can do my entire driver skills with only two turns!


Just don’t use WD40 though, because it is illegal in IQ.

i dont know how to do that- i have never used google drives
do macs even have google drive?

go to google

go to google drive

upload file

share link

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one has omni wheel in the centre and the other had tration wheel in the centre.
Note- the four drivetrain wheels are standard traction wheels.

you need to turn link sharing on in settings of the files. we can’t see anything when we press the link

[quote=“Ethan5956F, post:18, topic:83934”]

it should work now…

can you send a close up pic of the strafe wheel from the front? i want to see how it’s mounted