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Wild thumper 6wd with WTC

Ok so two questions today. I built my 6wd wild thumper with the wild thumper controller. Controlling it via rc tx futaba 7c 2.4ghz. It drives pretty great but it drifts a bit to the right when I push forward on the stick. When I have the WT up on my stand and I very slowly move my stick forward to the point of first wheel movement, the left wheels begin turning before the right. Does anyone know and troubleshooting steps I could follow to remedy this? Againg the drift to the right isn't really that bad, it just bugs me :) Second question: On the wild thumper controller, the battery terminals are big enough for the 12 gauge stranded wire I have from RadioShack , it just won't fit into the terminals. So I am using 14 gauge strandarded wire I found at homedepot ( http://www.homedepot.com/Electrical-Wire/Southwire/h_d1/N-5yc1vZbm7vZ4mm/R-202316260/h_d2/ProductDisplay?catalogId=10053&langId=-1&storeId=10051#.UOhNhBB5mK0 ) <--- thats a link o the type of wire I got.... So the wire is rated for "15 allowable ampacities".... This is obviously less than the 30amp wire recommended.... So my question is, what gauge wire are others using and how are they fitting them into the WTC battery terminals, or am I just purchasing the wrong type of wire? Also would this wire limit the performance (ie torque) of the motors? Thanks ahead of time ! High current motors are a new thing for me! Marko

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I dont think adjusting the Leftcenter, Rightcenter and RCdeadband values is going to correct my issue.  I have tried this with numerous different setups and nothing will correct my issu.  Additionally, my transmitter signal is not the issue because if i am utilizing the "Mix" feature, so i have one channel for throttle and one channel for steering, then when I only push forward or reverse on my throttle channel, the controller is only handeling one set of input, because steering remains null and has no impact.

I further tested this by only connecting one channel from my receiver to the controller board.  So at this point, the controller is only mixing one channels values, so this eliminates any potential issues stemming from your theory on the tx center position values because there is only one value and its being "mixed' for both motors.  

I get the feeling there is something in the code is not mixing the forward/reverse signal properly, thus allowing the right motors to begin turning before the left, but I just can pinpoint it.  

I feel like I have ruled out the transmitter being an issue.

Any thoughts?

Marko

Hi,

I have a Wild Thumper 6wd and a WTC.

You have to note there are 6 motors. Even in motors of same batch, is normal some slight difference. I think that's why left channel responds before. It's not satisfactory, but is normal, you have to correct the trajectory by control yourself :(.

Or do some code to change regulate the voltage supply slight less(or some delay) on left channel ;). Not beautiful, but if you really want a straight line, some workarounds need to be done.


PS: it's VERY RARE a vehicle with differential steer(like tanks, bulldozers and WT 6wd) do a perfect straight line, cause that's not the purpose of these vehicles..

I kinda was thinking on those lines as well, that it has something to do with the fact that we have 6 different motors.  But what I suppose that i dont understand is that all 3 motors on one side begin turning before the other side motors.  Additionally, if I swap the wire going to the motor controller so that the "left" motors go the WTC right motor out and the "right" motors are wire to the left motor output, the problem is still the same, but its consistant with the output.

So its always the left output that begins to provide power to the motors first, regardless of which set of three motors is being powered (ie. left side or right side).  I guess that what is confusing me.  I would suspect that the out of the motor controller would be consistant for both left and right motor outputs.  I have yet to measure the actual output yet with any multimeter but that will be my next move so i can more clearly understand what exactly is happening to see if I can figure out some sort of solution.

I know this is not really THAT big of a deal... I just have this itch that when I push forward, the damn thing goes forward! :)  at the end of the day, I dont really care, I just am compelled to know WHY :)

 

Thanks again!

Marko

I'm not an  "electronic expert", so, all things I tell you now may be wrong.

In the beginning I thing WTC was weak and don't deliver the current the motors need, what does not make any sense, since WTC was designed to work perfectly with WT6wd.

So I changed the Leftmaxamps and Rightmaxamps to a higher value, and turn VR1 and VR2 random, without any measure (:D). And, Don't know if it's a placebo effect, but performance gets better.

I made a question about these regulators, and OddBot(the WTC's designer) says these reguletors are only for reading the voltage decay on fuses and do not interfere on actual performance, so, ok, was a placebo effect. But... something change...

Knowinf this, there are a possibility of the fuses contacts "grip" embraces the fuses with different force, giving mor current to one or another. So, I soldering then and now I think is ok.

I recomend you to solder the fuses before make the sugested calibration of VR1 and VR2:
https://sites.google.com/site/daguproducts/home/tutorials/understanding-wild-thumper

It's a great product, but really need some workarounds for perfectionists :D.

For curiosity, here is mine in action, Internet Browser controlled by a friend 900 km away(about 560 miles, if you from USA :D):
http://www.youtube.com/watch?v=5xNUsHhzaBU

And here I control from my office:
http://www.youtube.com/watch?v=rUSnQGpNmdU

Ya im no expert either, this is all a learning experience for me as I go.

I have soldered my fuses, but I will check to make sure the solder joints are clean and fully contacted on the fuses to rule that out, i suppose that really could have an impact.

I also dont think that adjusting the VR1 and VR2 would make any difference, as OddBot point out, they are just for measuring the current draw.  

I will have to take a close look at the code...again... and see if I can figure something out, but I dont think its in the code as the code is very straightforward.

Thanks for your videos though!  Always neat to see.  What gear ratio do you have on the motors? 34:1 or 75:1? Just curious.  I had another thread I opened questioning the amount of torque at the wheels (i have 34:1 gear ratio on motors).  If I hold a single wheel and give full throttle, the wheel doesnt turn and doesnt seem to give much torque... maybe its just not that strong of a motor and isnt meant to, but I dont know.  I just notice that when im on some sort of very uneven surface and, lets say, the center wheel is 'stuck' sort of on a rock or something, it just doesnt have enough torque to turn the wheel and stays locked up.

Marko

Mine is a 34:1 too...
As I use an internet conection to control, better if I was get a 75:1 :P, as I don't need speed, but torque... The next one i will try to made by myself, with higher torque.

If you hold a wheel, oh boy... I had a problem climbing a slope. The front wheels spins in air, the middle wheels skidded a little and rear wheels stuck... for some seconds... and burn a motor(think for being stuck in the same position).

As this particular event (wheel stuck or 2/3 of the wheels don't touch the ground) is rare in a chassis with this kind of suspension, I don't think you need worry about... Just, dont try to clim a slipe with more than 15 centimeters :D. Uneven surface, mud, glass, rocky terrain, gravel, etc, its ok. High stairs/slopes, because of 90º angle put some wheels in the air and, this way, don't distribut torque equally.


Ok

 

If you are using thr RC to control the Wild thumper, why don't you just adjust the trim to correct the drift? It's likeyly your transmitter is not sending precise 1500uS center position values. If you are using one of the fancy transmitters that can be programmed then make sure all your setting are correct and that you are not mixing channels.

You can also go into the constants tab of the code and adjust the Leftcenter, Rightcenter and RCdeadband values.

When a wire is rated for a certain current it is a continuous rating. The cable is usually rated based on voltage drop over a certain length. In the case of the Wild Thumper, the lengths of wire are relatively short and to draw 30A, all 6 motors would need to be stalled (unlikely to happen). In most cases the average current will be less than 10A unless your robot is heavy and climbing a steep slope.

Use your 12 gauge from the battery to the terminal strip and then use the 14 gauge from the terminal strip to the Wild Thumper controller. That will be fine.

Awesome... Thanks again for the informative responses... I will give your suggestions a shot on the different motor speeds, appreciate it. Marko