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mallster
12-02-2008, 12:26 AM
Hello All,

Looking for some help or suggestions from some robot gurus to help me with me first go at building a robot.

Rough Parts List:

1 x surveyor stereo camera (did order the expansion board, however i would advise holding-off as there seems to be a major problem with supply)
1 x pico motherboard
1 x Johnny 5 kit
3 x 7.2v 5000mah nimh(paralell)
1 x 12v 4000mah nimh
1 x 3" track kit (ordered seperately)
2 x banebot planetery motors
1 x 2x5 sabertooth motor driver (may be a little small?)
4 x rc shocks for tensioners on the tri-tracks (not shown)


Questions:

Do you think the servo attachment to 3 tracks will work (see jpg).? (will add spring shocks to help take the 3kg weight of wall-e) Is it possible to remove power from servos when not being used?

Im hoping some firgelli L12 linear rc actuators will be available soon for the arms. If you have ever come across anything more suitable around 140mm 170mm retracted please let me know.

Feel free to dish-out on me wall-e robot especially if you can see something that just doesnt look like itll work in the servo department. Never used servos before.

Using the new P700 10L Pico motherboard but can not seem to get any action apart from the fan spinning twice upon turning the power on? - This model says it has 12v integrated power supply so i took that as meaning it could be run run straight off the 12V nimh pack (measured 12.6V).

Still a work in progress, but if anyone wants the cad model just let me know.

4mem8
12-02-2008, 12:58 AM
mallster: This is pretty cool stuff you are doing here, I thought my Wall-E was pretty good, but this one is awesome,I look forward to your future posts here.

Adrenalynn
12-02-2008, 01:06 AM
Welcome to the forum!

To address one of your questions - if power / signal is removed from a servo, it goes "slack" with no holding torque at all.

lnxfergy
12-02-2008, 08:40 AM
Hello All,

Do you think the servo attachment to 3” tracks will work (see jpg).? (will add spring shocks to help take the 3kg weight of wall-e) Is it possible to remove power from servos when not being used?



I guess the question really is: what servos, and what do you plan to do with the servos? Obviously, the intent is to change the angle of the tracks with relation to the ground (which is really cool), but the real question is: with what servos and under what condition? There's quite a bit of weight up top - so you are gonna need a hefty servo. Also, is the intent only to change the angles when rolling? If not, I'd be concerned that when the tracks are static and you try to adjust the servos, the friction of the tracks on the surface will be so high that the servos probably won't have the power. If you are rolling forward/backward when you adjust the angle you should get a little more slip. Also, I'd be concerned about the force exerted on the servos when the robot skid steers to turn!

Another servo that needs to be hefty is the one inside the robot at the base, that moves the arm location (it's got a big lever, with lots of arm parts on the other end... so a large load)

And as adrenlynn said, it's possible to remove power, but the results won't be good (no holding power). You might consider using a linear actuator to angle the tracks instead of a servo, as it would have holding strength without power, and I would think it would be better suited for the stress of skid steer...

Oh, and this is getting out of control -- too many people making me want a pico-itx and a lynxmotion track set...

-Fergs

4mem8
12-02-2008, 11:16 AM
Oh, and this is getting out of control -- too many people making me want a pico-itx and a lynxmotion track set...

-Fergs


Yes those Lynx tracks damn good value Inxfergy. Go on get a set and an ITX.

mallster
12-04-2008, 12:44 AM
Thanks for the suggestions Fergs,
The intent of the of the track servos was to keep the track angle change to a minimum and move wall-e up and down and tilt! I'm hoping a bearing joint at the bottom of the servo will work.
Most of the servos are 645mg, but looking to order 4 x 5990tg's for the tracks and arms. Having never used the ssc32 board I am wondering if the little thing can put enough amps through to drive all servos?

Adrenalynn
12-04-2008, 12:53 PM
As I noted before: Yes and No. The SSC32 can't directly power the servos from its onboard regulator, nor can any other hobby-grade servo controller. BUT: the SSC32 has an external power input for each bank of servos. You can either run a servo battery of the appropriate size, or a high-amperage switching regulator into the external power inputs and you're set. I use this: http://www.castlecreations.com/products/cc_bec.html 4mem8 uses one of those as well.

I tried to buy one of the less expensive switchable units, but the companies making them/selling them are a PITA to deal with. "Got a question? Don't as us, we don't know. Post it to the forum and maybe someone there can guess." Long delivery times, crummy warranty, zero support. For an extra few dollars I bought from a USA manufacturer/designer/support system that was actually there for me...

ScuD
12-04-2008, 02:44 PM
Thanks for the suggestions Fergs,
The intent of the of the track servos was to keep the track angle change to a minimum and move wall-e up and down and tilt! I'm hoping a bearing joint at the bottom of the servo will work.


From what i can tell from the design right now, I'm afraid your servo's aren't going to last long. You're putting them at high stress levels when just driving around.

Unless that is, the tread motors "lean" against the body so the servo doesn't need power to keep the treads straight, it's blocked and can only move the treads uhm.. 'outwards' by a lack of better way of explaining myself.

Even so, I would opt to keep the axis as-is (where the servo is right now), but just make it an axis, remove the servo, put the servo in the body and use a lever to push the treads more at the top (like above the tread motors) to increase leverage and lower stress on the servo.


Man I have completely lost the ability to express the things inside my thinking... egg.. round.. thingy..

Adrenalynn
12-04-2008, 03:28 PM
Man I have completely lost the ability to express the things inside my thinking... egg.. round.. thingy..

Casaba? Gourd? Melon? Ten pounds of ugly fat? :tongue::tongue::tongue:

SteamBoat
12-04-2008, 04:04 PM
I know this thread has gone into being about the eggy shaped thing but I thought I'd throw in my two cents. As I'm having problems with my gourd you just might have to use your melon to understand what I'm trying to say.

From what I understand you are trying to make it so you can tilt the body/tracks when you want too but also hold the system at a specific angle for the majority of the time. I was wondering if you could use a brake system. What I'm thinking about is something like I saw on a remote controlled off-road rig. It was a disk break hooked up to the throttle. Stopping force was applied by reversing the throttle servo which closed the calipers. That's not exactly what I'm suggesting here but that's what was on that vehicle.

Use a shaft that controls the angle of the tracks. On that shaft put a break system that is held normally closed/tight with a spring so that when there is no power supplied it holds the angle you want. Then, when you want to change the angle you apply power to the servo that will change the angle and then use a servo to open the brake. After the angle control servo has made the move then remove power from the servo holding the brake open before you remove power from the angle control servo.

An additional servo but lower power consumption and less wear. No?

Is that what you were trying to do?

MArk B.

Adrenalynn
12-04-2008, 08:01 PM
If I understand where you're going with that, Mark, you could also have it "fail safe" and save some power/servo-wear by having the brake spring-engaged by default. The servo opens the brake and the rod then gets run throw the brake to the appropriate point at which time the servo disengages and the brake "fails" back to freeze the rod ???

SteamBoat
12-04-2008, 11:33 PM
I told you that you were going to have to use your noodle to understand what I was taking about. :-)

I was trying to describe it faile safe as you did. A sprink keeps the brake on all the time and only when you want it off does the survo engage.

http://www.oversizerc.com/pictures/3237/9/1164659-1.jpg
http://www.oversizerc.com/p/514107/15-scale-upgrade-front-disk-brake-kit--traveller-bigfoot-15-scale.html

Take the wheel hubs in the links for example. Mount something like these on the frame. Then, mount the pivot point of the tracks on the spindle. Then, put a spring on the cable that tightens the brake so it's always on. Then use a servo to release the spring to let it rotate.

Then, mount servos on the body and connect them to the tracks to control the tilt. You activate these only when the brakes are released.

If you never want the tracks to tilt at different angles then you could mount the tracks on an axle that runs all the way across the body of the bot and then use one brake and one servo instead of the pairs.

Is that a better explanation?

MArk B.

darkback2
12-04-2008, 11:55 PM
You could also use a screw rig with a continuous rotation servo. The servo turns a screw which in turn tilts the tracks in or out..

DB

happytriger2000
11-17-2010, 08:05 AM
Hello All,

Looking for some help or suggestions from some robot gurus to help me with me first go at building a robot.

Rough Parts List:

1 x surveyor stereo camera (did order the expansion board, however i would advise holding-off as there seems to be a major problem with supply)
1 x pico motherboard
1 x Johnny 5 kit
3 x 7.2v 5000mah nimh(paralell)
1 x 12v 4000mah nimh
1 x 3" track kit (ordered seperately)
2 x banebot planetery motors
1 x 2x5 sabertooth motor driver (may be a little small?)
4 x rc shocks for tensioners on the tri-tracks (not shown)


Questions:

Do you think the servo attachment to 3� tracks will work (see jpg).? (will add spring shocks to help take the 3kg weight of wall-e) Is it possible to remove power from servos when not being used?

I�m hoping some firgelli L12 linear rc actuators will be available soon for the arms. If you have ever come across anything more suitable around 140mm � 170mm retracted please let me know.

Feel free to dish-out on me wall-e robot especially if you can see something that just doesn�t look like it�ll work in the servo department. Never used servos before.

Using the new P700 10L Pico motherboard but can not seem to get any action apart from the fan spinning twice upon turning the power on? - This model says it has 12v integrated power supply so i took that as meaning it could be run run straight off the 12V nimh pack (measured 12.6V).

Still a work in progress, but if anyone wants the cad model just let me know.


Very nice 3D model, did you draw those wheel tracks?. I'm creating a 3d model for my wifi robot platform and I'm using a 3" wide tracks but cannot find the exact model for it, may I ask for the dxf file of that track?

Freddy

mallster
11-18-2010, 03:50 AM
Hi Freddy,

I got all my Lynxmotion models from their website. I just copied/patterned the 2" link to match the 3".

http://www.lynxmotion.com/s-5-ses-3d-models.aspx

happytriger2000
11-19-2010, 01:38 AM
Thanks Mallster!!