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Large J5 style robot

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Posted: 2007-08-26 11:01 
 Post subject: Re: Large J5 style robot
Not only that, but were getting into the problem of size and weight when you add all of this equipment. Realistically this could become as large as a ride-on if your not careful. I think something low-ground and wide would suit this feild of work so that it is not to tip, flip or wobble on the un-even and wonky terrain.

just my opinion :?

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Posted: 2007-08-26 14:11 
 Post subject: Re: Large J5 style robot
ChazBCook wrote:
Question about converting ac to dc.
If i were to buy a this cheap generator http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200313480_200313480
it puts out 120 v with 1000 watts to convert to amps (Amps = Watts/Volts)
1000 watts/ 120 v = 8.3 amps
how would i convert that to dc
if i convert the volts to 13.8 it gives me 72.4 amps but i'm lost the the ac to dc convertion. 72 amps would be great but don't believe i did that right.

What you are talking about (ref: Ac to DC conversion) is a DC Power supply, the same type of power supply you would plug into a wall outlet at home. In the 1KW range these are not small things, however, unless you are looking to use all 1KW of output from the generator there is nothing preventing you from just using the size power supply you need. So if you need 20A at 13.8V then go buy a 20-25A power supply and run it off your generator. Alternately if you peak load is say 35A but most of the time it's less than say 20A you can use a small garden tractor battery as a buffer, using a 20A power supply to float charge the battery and handle most of the nominal load while allowing the battery to handle the peak loads. Anyway, we use a lot of Astron supplies at work, several 20A and 35A ones and a few 50A ones. We actually have an 80A peak load product wired up as I described with a battery and 50A supply on a fixture. The stuff is expensive brand new although sometimes you can pick them up reasonably cheap on ebay (but you need to be careful about ones having been "repaired"). ;)


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Posted: 2008-02-18 18:58 
 Post subject: Re: Large J5 style robot
I'm building something on a similar size scale as you (3 sets of 3" tracks per side). I also plan on using a chain drive (probably a two-stage chain reduction) since I need to gear my motors down somewhere between 1:9 and 1:11. I was wondering if you could provide any additional info on how you're attaching your drive sprockets to the lynxmotion hubs. I know you said you made some custom axles, but I can't find sprockets anywhere with a bore less than 1/4" (this would be easy if I could find sprockets with a 6mm bore, but no luck).


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Posted: 2008-02-18 19:07 
 Post subject: Re: Large J5 style robot
dts3p wrote:
I'm building something on a similar size scale as you (3 sets of 3" tracks per side). I also plan on using a chain drive (probably a two-stage chain reduction) since I need to gear my motors down somewhere between 1:9 and 1:11. I was wondering if you could provide any additional info on how you're attaching your drive sprockets to the lynxmotion hubs. I know you said you made some custom axles, but I can't find sprockets anywhere with a bore less than 1/4" (this would be easy if I could find sprockets with a 6mm bore, but no luck).


you could always drill out the sprockets with a dremel or drill press to 6mm.

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Posted: 2008-02-18 19:22 
 Post subject: Re: Large J5 style robot
I am using 1/4" stuff with everything I do... 6mm is only like .013" or something away from 1/4... so I figure thats in the noise.

I will be driving my 3" tracks with a roller chain sprocket with a 7/8" bore, attached to Jim's 3" idlers. It should nestle between the injection molded track sprockets quite well. That in turn is connected via #25 roller chain to a 1/4" axle (via another sprocket of course), and then to my 6mm shafted motor (PGHM-02) via what mcmaster calls a "spider" coupling. (at least thats the current plan)


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Posted: 2008-02-18 19:28 
 Post subject: Re: Large J5 style robot
Well, the smallest bore sprocket that I can find is 1/4" which is 6.35mm, so if I drill anything out it would have to be the lynxmotion hubs. How difficult would this be to make sure I drill it out properly with a dremel (I don't own a drill press). I'm assuming that to prevent wobble this needs to be perfectly centered (I'm shooting for between 200-350 rpm depending on how I decide to gear it).


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Posted: 2008-02-18 19:32 
 Post subject: Re: Large J5 style robot
Sienna wrote:
I will be driving my 3" tracks with a roller chain sprocket with a 7/8" bore, attached to Jim's 3" idlers.


I guess this is the part I'm confused about. Does the sprocket you use bolt right up to the 3" idlers?


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Posted: 2008-02-18 20:22 
 Post subject: Re: Large J5 style robot
The 3" idlers (HUB-13) have an outer diameter of 0.865". The roller sprockets I am looking at have a bore of 0.875", and come with a keyway and set screw.

I plan to place the roller chain sprocket over the large part of the idler (i.e., the center), and 'sandwich' it between the two LM Track Sprockets.

At first I will try just the set screw, see how well that holds up. If I need to, I will find some way to add a keyway to the idler.


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Posted: 2008-02-18 20:24 
 Post subject: Re: Large J5 style robot
Quote:
I will find some way to add a keyway to the idler.


If you have access to a CAM, this would be simple to do. My high school has a CAM in the metal shop.

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Posted: 2008-02-18 22:35 
 Post subject: Re: Large J5 style robot
Sienna wrote:
The 3" idlers (HUB-13) have an outer diameter of 0.865". The roller sprockets I am looking at have a bore of 0.875", and come with a keyway and set screw.

I plan to place the roller chain sprocket over the large part of the idler (i.e., the center), and 'sandwich' it between the two LM Track Sprockets.

At first I will try just the set screw, see how well that holds up. If I need to, I will find some way to add a keyway to the idler.


Could you post a link to these sprockets?


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Posted: 2008-02-18 23:48 
 Post subject: Re: Large J5 style robot
Look at McMaster.com, catalog page 1012, starting at item 2737T13, and continuing down. I plan to use a 20 tooth myself, to make sure it fits within the radius of the plastic sprocket.


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Posted: 2008-02-19 03:35 
 Post subject: Re: Large J5 style robot
Thanks for your help!

Sorry to the OP for hijacking this thread


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Posted: 2008-02-23 12:23 
 Post subject: Re: Large J5 style robot
I found most of my mechanical parts at Robot MarketPlace. Sprockets, Chain and I think I bought 1/4 inch hubs from there also. Replaced so many parts in so many different tests its hard to remember.

After many tests the base is way to small for any sort of large scale mowing. Plus with the tracks it leaves a 3 inch uncut edge. The platform is great for running around the yard but the gps didn't work as i planned.

The tracks them self have preformed great there is wear but nothing major even used on concrete or grass. Only trouble i had was was in gravel but that is a flaw in my tracks design.

For some reason i can't see the pictures i posted on this post any clues why?


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Posted: 2008-02-23 13:48 
 Post subject: Re: Large J5 style robot
Great to hear, I'm looking forward to getting something built. How was the hill climbing ability of your setup on grass? Did you ever do any tests to see how much it could pull? Have you tested these tracks in snow/ice?

What was the problem with the gravel? Maybe I can avoid this problem

I'm not sure about the pics; do you have to have a certain number of posts before you can add pics? I know some forums are set up like that


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Posted: 2008-02-23 13:55 
 Post subject: Re: Large J5 style robot
Pictures can't be posted to the board itself. One has to use links to the picture that resides on another web site.


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