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hank van buren
09-29-2008, 07:38 PM
This is just an idea,·why could the motor and wheel mount with the proper reduction be used on my 4 wheel robot for steering. It has all the capabilities of a regular servo except with a lot more power. Hank

allanlane5
09-29-2008, 08:00 PM
Differential Drive used for steering on a 4-wheeled robot does not work as well as on a two-wheel robot with a third drag-wheel. Having said that, it CAN work, it's just how much turn you get depends heavily on the materials of the floor you're on and how much wheel slip you have.

In the worst cases, for long wheel-base robots with very sticky tires, differential steering doesn't work at all.

SRLM
09-29-2008, 08:30 PM
If I'm not mistaken, the quadrover uses 4 wheel differential steering.

allanlane5
09-29-2008, 09:28 PM
The "quadrover" does not have what I would call a "long wheelbase".

Zoot
09-29-2008, 10:07 PM
I think Hank may mean using the motor/position controller as a "steering" motor for Ackerman type steering (essentially using it as a giant servo).

Hank -- if that's the case, the Parallax motor may overkill for this, plus I don't think the encoders will give you the steering resolution you might really want. You could consider some of the geared down (super powerful) servo gear adapters over at http://servocity.com, e.g., 350-2000 oz. in. of torque, at 180 degree rotation: http://servocity.com/html/servo_power_gearboxes.html


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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php (http://1uffakind.com/robots/povBitMapBuilder.php)
1uffakind.com/robots/resistorLadder.php (http://1uffakind.com/robots/resistorLadder.php)

Post Edited (Zoot) : 9/29/2008 3:12:37 PM GMT

hank van buren
09-30-2008, 12:12 AM
Hi Zoot
That's exactly what I had in mind the system I use now is to slow 4,5 sec I use Ackerman steering. I am after a max speed of 6 MPH. The car will be GPS controlled. You might take a look at the pictures. Hank·

SRLM
09-30-2008, 12:22 AM
Does that have both differential and car type steering? It looks like in the back is the motor mount kit and in the front is some sort of homebuilt wheel turning device. You could get some interresting motions from such a device.

@allanlane
No, I don't think the quadrover has a long wheel base. Rather, I was just giving an example of a working solution.

Zoot
09-30-2008, 12:25 AM
Nice! Do you have steering control on it now? Looking at it, you might also want to consider servo sprockets with a belt or chain (you can get small sprockets with standard servo horn splines) that might make it most flexible, and allow for looser tolerances.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php (http://1uffakind.com/robots/povBitMapBuilder.php)
1uffakind.com/robots/resistorLadder.php (http://1uffakind.com/robots/resistorLadder.php)

hank van buren
09-30-2008, 12:48 AM
Yes I have full· GPS control over the car Just like its bigger brother but a lot more economical it also uses a Garmin 15L for guidance. I am limited on speed because of the steering servo. I am enclosing a picture of a recording of the track the speed was 1.85 MPH. tota lenght of track 812·Feet.·Hank·

hank van buren
09-30-2008, 12:59 AM
Hi SRLM,

It is driven by 2 each motor mounts the steering is a car type I am currently trying my luck at differential motion of the two motors (not easy). Hank

Zoot
09-30-2008, 01:19 AM
I am a huge fan of differential steering, *however* if you want this platform to move *fast* then Ackerman steering provides serious improvements in stability, etc. For differential steering, consider an industrial caster (until the new Parallax tail-dragger comes on-site!) -- you can get them with really nice swivel and wheel bearings, in large sizes (up to 10") in a variety of tread and tire configurations. I picked up a 5" caster with bearing that works really really really well on a 50 lb 'bot for about $15 at a local wholesaler.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php (http://1uffakind.com/robots/povBitMapBuilder.php)
1uffakind.com/robots/resistorLadder.php (http://1uffakind.com/robots/resistorLadder.php)

Ken Gracey
09-30-2008, 10:04 PM
hank,

I'm interested in knowing how the motor mounts and wheel kit worked out in this application. I'm not looking for product praise, but any feedback you may have so far to provide us. We're selling a good number of units but our customers are pretty quiet!

Thanks,

Ken Gracey
Parallax, Inc.

Steve in NM
10-01-2008, 01:41 AM
Zoot said...

I think Hank may mean using the motor/position controller as a "steering" motor for Ackerman type steering (essentially using it as a giant servo).


If that *is* the case Hank, here is a competitor's product to make "monster servos.":
http://www.lynxmotion.com/Product.aspx?productID=648&CategoryID=52

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hank van buren
10-01-2008, 09:12 PM
Hi Ken
First of all I like to say the motor mount is a excellent product· with good produt support· (if you like it or). I have solved the remote R/C,·forward and reverse· with the exception of differential drive. I will keep you informed of any progress we make·Hank

hank van buren
10-01-2008, 09:22 PM
Hi Steve, I wish I would have known about this product before it would have saved me a lot of time I am going to order on Tanks. Hank

Post Edited (hank van buren) : 10/1/2008 2:56:50 PM GMT

jpyle
10-08-2008, 11:45 AM
Hank, i just wanted to say that your platform looks great. What I see is easy to maintain, conversion easily done and plenty of power. I beleive your steering system is very workable. I have had great sucess with it in the past myself. Keep up the good work, and updates. Just my 2 cents worth----John