R/C aircraft tail wheel or skid steering (any recommendations?)

Dobermann (Black Dog Systems, LLC)

Hi Folks!

As usual I am facing another crisis. I guess its just me not being able to make a sane decision on my own. The designing of any robotics project can be very daunting indeed. I have reviewed as much material online I could find regarding the use of the R/C aircraft tail wheel assemblies and skids (such as pull knobs). It seems that some people have success with using the R/C aircraft tail wheel assembly while a few people state that it causes problems. I like the idea of the tail wheel assembly, but I've read that sometimes is certain robots that it can 'trip' up the steering. (ie- tail wheel turns in an odd position and places drag on the steering) that causes the robot to veer off course. I have built successfully other robots using the skid method (pull knob). These seem to work but wear out over time, since they are only cheap Home Depot plastic knobs. Some robotic designs I have seen employ the use of a servo to steer the 'third' wheel. I'm already using two Hitec quarter scale HS-805BB's as the main drive servo's, it seems silly (maybe) to use a third servo to do what the two Hitec's are already able to do. I'm just looking for any feedback to push me in the right direction. Thanks!!!


Respectfully,
Michael G. Jessat

dandreae

Have you checked out Boe-Bot's back wheel?· It's a regular urethane ball with a hole drilled down the center.· It works really well.· What size is your robot?

Dave

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Dave Andreae

Tech Support
dandreae@parallax.com
[noparse][[/noparse]url]Http://www.parallax.com[noparse][[/noparse]/url]

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Dobermann (Black Dog Systems, LLC)

Hi Dave!

Thanks for your reply. My robot is 8"LX6"WX3"H and should be around 2-3 pounds when completed. I have looked at the ball used on the BOE BOT, it looks really durable. Can these be ordered as a seperate item? I'm still pondering the R/C tail wheel, I guess only because it looks cool? Not to say the BOE BOT skid ball is lame, I really like it too! I am trying to get this project right the first time around (this time). Like I said, I have built two robots before, both turned out to be marginally useful. Poor design and weight distribution usually led to me giving up any hope to make them totally useful. The plastic skids (pull knobs) only lasted a few weeks before they wore down to the screw holding them in place. I was running them on various surfaces ranging from short pile carpet to a very smooth cement floor in my basement workshop (has a surface like glass, but must still be abrasive). What this really amounts to is the fact that I just couldn't face another failure. This time around with the knowledge I gained from the previous design flaws and other related issues, one might think the third time is the charm. In my case its making me go almost to the point of insanity. I'm rethinking every aspect of this current robotic project hundreds of times before making a decision. This hobby should come with a warning "Pursue at your own risk, may cause sleepless nights, do not drive or operate machinery that you might be tempted to remove interesting parts from. At first sign of overdose, contact Parallax Customer Support and buy the BOE BOT!"

Thanks again Dave!

Respectfully,
Michael G. Jessat

Steve Joblin

I use ball transfers (you can find them at McMaster.com).· Make sure you get ones that are "ball down".· The other idea is to use an "onmi-wheel".· There are really neat wheels that move forward, backward, and sideways. Check out www.acroname.com/robotics/ info/ideas/omnicaster/omnicaster.html info/ideas/omnicaster/omnicaster.html

Dobermann (Black Dog Systems, LLC)

Steve,

Thanks for your reply. Yes, they really do look interesting! How do the ball transfers perform for you?


Respectfully,
Michael G. Jessat

Steve Joblin

I have found that for my use, the ball transfers are great!· They are fairly inexpensive and don't get hung up as floor surfaces change (going from hardwood to carpet for example).· You can see a picture of a robot that I built with a ball transfer at my website... http://spaces.msn.com/members/roebotz

Steve

dandreae

Yes you can order the balls separately.· The part number is 700-00009 for the polyethylene ball.

Steve,

Your wheels that are made out of sink drains, look awsome.

Dave

Dobermann (Black Dog Systems, LLC) said...
Hi Dave!

Thanks for your reply. My robot is 8"LX6"WX3"H and should be around 2-3 pounds when completed. I have looked at the ball used on the BOE BOT, it looks really durable. Can these be ordered as a seperate item? I'm still pondering the R/C tail wheel, I guess only because it looks cool? Not to say the BOE BOT skid ball is lame, I really like it too! I am trying to get this project right the first time around (this time). Like I said, I have built two robots before, both turned out to be marginally useful. Poor design and weight distribution usually led to me giving up any hope to make them totally useful. The plastic skids (pull knobs) only lasted a few weeks before they wore down to the screw holding them in place. I was running them on various surfaces ranging from short pile carpet to a very smooth cement floor in my basement workshop (has a surface like glass, but must still be abrasive). What this really amounts to is the fact that I just couldn't face another failure. This time around with the knowledge I gained from the previous design flaws and other related issues, one might think the third time is the charm. In my case its making me go almost to the point of insanity. I'm rethinking every aspect of this current robotic project hundreds of times before making a decision. This hobby should come with a warning "Pursue at your own risk, may cause sleepless nights, do not drive or operate machinery that you might be tempted to remove interesting parts from. At first sign of overdose, contact Parallax Customer Support and buy the BOE BOT!"

Thanks again Dave!

Respectfully,
Michael G. Jessat

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Dave Andreae

Tech Support
dandreae@parallax.com
[noparse][[/noparse]url]Http://www.parallax.com[noparse][[/noparse]/url]



Post Edited (Dave Andreae (Parallax)) : 6/21/2005 11:59:33 PM GMT

Dobermann (Black Dog Systems, LLC)

Dave,

Thanks for the part number. I'm going to be ordering several of them to evaluate, just as soon as I make my mind up about the PSC controller. I have the Mini SSC II, but am having trouble with it. Looks like the PSC will be the better selection.

Thanks again!!
Michael G. Jessat

Dobermann (Black Dog Systems, LLC)

Steve,

Your creations are awesome!! I'm still reeling from the use of the sink drains for wheels. I would have NEVER thought about using them for that purpose. Its a grand idea! I only wish I was that resourceful, I'm still stuck in the buy everything from the local hobby shop mode. And, I'm quickly learning that its not only more costly, but more times than not the stuff I end up buying doesn't perform well, or is just plain Smile. I have so many Du-bro and Lite Flight wheels that just plain didn't cut the mustard. They almost always end up distorted (too much weight - Lite Flight), or too heavy (Du-bro) for the servo's to turn. Maybe I'll give them to my dog to play with, she seems to be attracted to them anyhow

Keep us updated with your future creations.

Respectfully,
Michael G. Jessat

P.S.- I did order the ball transfers today. I'm going to place an order tommorrow with Parallax for a PSC and BOE-BOT roller balls.
I am going to evaluate them both, as weight is a real factor I'm struggling with again. So many features, so little space.