We got ours working better, without the weight of the rest of the robot on it pops up to level three in about two seconds. It’s getting interesting.
post a video excited to see it in person at North.
That sounds awesome. My energy-based calculations for a 140# total robot weight (including batteries and bumpers) showed a single motor climb operating at 50% peak power* was theoretically possible in about 1.5 sec, and that about 2 sec was likely the practical limit for a single-speed transmission at the risks I’d normally take.
- On the correct side of the power curve, this corresponds to ~15% of stall torque, and ~85% of free speed.
hmm…me thinks you have cameras in our shop! LOL
We are aiming for a robot well under 140 lbs, actually a total weight under 100 lbs.
We also strapped 30 lbs to the chassis with the climber, and it still goes up ok, but it makes the alignment thing slightly trickier. We are working on ideas to make that problem go away, too.
But come on folks, post some more videos! Fail videos are encouraged, we all learn so much more from them.
Suggest cutting the frame and allow the bars to rotate up and out of the way.
It’s a fun game figuring out how far the bars need to go back into the frame, and also how to keep the back of the robot up without it resting on level 1. As I mentioned, we spent quite a bit of time modeling the mechanism, then we had to figure out how to get it to move the way we expected it to move.
- How do you power the wheels at the bottom of the tubing,?
- What kind of wheels are they?
- What kind of setup do you use to lower tubing?
1.You can see at the top of the back “leg” there is a Andymark NeverRest 60:1 motor mounted with a chain running inside the tube down to the hex shaft. Only the back wheels are powered.
The wheels are Andymark 2" stealth wheels
We are using a rack and pinion setup to lower the legs. Powered by miniCIMs connected to 30:1 VP gearboxes.
The legs look like they are made of 1x2 tubing, what kind of chain are you using running down the tube?
We may or may not, totally conjecture, may be doing something similar, and are powering our totally not-the-same “stilts” with ball screws, and our back wheels with a BAG motor.
Where did you find a sprocket small enough to fit inside the tubing, Had to have a diameter smaller than 0.9 inch?
We are using a 16t vex sprocket with 1/2" hex bore on the axle end. It has a diameter (w/ chain installed) of 1.503". Since the tube is 2" wide (approximately 1.75" inside clearance) it has plenty of room. On the motor side we are using a 16 tooth tetrix sprocket and hub that interfaces with the 8mm shaft of the NeverRest motor.
We just had a bunch of the NeverRest motors from our FTC days. They are not tough or powerful enough for most FRC applications, but we chose them here because of their light weight, compact size and low speed (without a huge gearbox).
I Looked like the wheels are coming out the 1 inch side of the 1x2, So i guess it comes out the 2 inch side.
Did you consider a VP 60 to 1 with a bag motor or a 775? Do you think a bag motor would be enough to move the robot?
did you use a lock mech to lock legs when you reached the desired length?
A bunch of our climber test videos are on our photo gallery. First iteration showed how much tension is actually pulled in the system so we moved away from chain to just a rope pull method. So far it’s lifted 108lbs without problems.
We have broken multiple sprocket teeth, multiple gear teeth, bent 7/8" aluminum tube and 1/2" steel hex shaft.
In any of the test videos if it gets the back wheels off the ground we call that a success because we know it can finish the climb but if we let it we risk breaking gear teeth since we don’t have sensors in place to stop it yet.
Yep, out the 2" side.
Honesty, we just stuck a NeverRest on there and it worked so we went with it. We liked the light weight and compact size.
Look at the motor specs of a NeverRest. It is one of the (if not the) weakest legal motors. If it can move the robot I doubt any other motor would have much issue. Our robot weighs around 80 pounds, for reference. Also, we were only running the motor at about half power in the video.
We do not have a locking mechanism. The 30:1 gearboxes, geared down a little more (I think 1.35:1) on the chain stage is enough to keep it from back driving. It if did back drive we would probably stall the motor out at low voltage for the time it took to do the climb.
What did you do for rack and pinion?
We bought a 20dp rack gear from McMaster-Carr, drill and tapped holes on the back to secure it to the aluminum tube. Then we are using a 20dp pinion gear with 3/8" hex bore from vex.