Ideas for mobile platform

The golf cart runs off SLA batteries, that is prolly a good bit of mass there. It is 3 wheeled, and therefore less stable. It is not intended for slopes beyond 20 degrees, on grass.

Building a platform capable of 20 mph is going to cost a lot more than 3K.

How about a youth ATV? like a Raptor 50 from Yamaha? Dimensions L x W x H 60.5" x 32.5" x 36" Seat Height 24.3" Wheelbase 40.6" Ground Clearance 3.0" Fuel Capacity 1.8 Gallons Dry Weight 237 Lbs.

Put an electric motor on there with a clutch for reverse.

I think I've mentioned this before in another post, but the rear engined snapper lawn mowers might be a good platform to try. If your project is a "not for profit" venture, you might be able to get a local lawn mower dealer to sponser an old used one for free (maybe for a little "NASCAR" type of advertising for the dealer on it). Otherwise a used one in decent shape might be had in the $500 range in the want ads. I've got one I've had for ~15 years and it is *rugged* and dead simple in operation. It hauls me (210 lbs) in and out of the ditch next to the main road without problems. The belt system that drives the blade would be very simple to use to drive an alternator and/or hydraulic pump to support onboard actuators. Foward-neutral-reverse and go-clutch in-stop is all simple push/pull actuation. Snappers are popular in the south, but not sure about the rest of the country. If you have a dealer near you, go buy and take a test ride around the shop to see how they work.

They are rugged, mostly because they are dead simple. Do they really have automatic transmissions? The ones I've seen have a sliding speed/"gear" control with notches, but they really don't have gears in the motion drive train, they are more continuously variable using a friction disk. I would bet that you could remove the teeth on the notches and use a servo to switch from low to hi ratio. Or just pick a ratio and bolt it down.

How about a dune buggy? Its a grown-up version of a go-kart. They're under $1000, powerful, fast, and look to be really hackable.

Heavy duty gearhead motors modified to be servos like in the below link from another thread could operate the go-neutral-stop pedel, foward-neutral-reverse lever, and turn the short throw stearing wheel. The MSRP for a new bottom of the line Snapper is ~$1,250 ($1,700 for electric start capability), well with in the $3,000 budget. If care were taken with the modifications, the moble platform could be returned to a lawnmower when the project is completed. Anything much lighter might do cartwheels when it hit a big rock or bump in the road at the higher speeds.

Having just finished with a DARPA Grand Challenge entry, I think you're underestimating the size of the job.

See

John Nagle Team Overbot

I agree with you, John, but the Grand Challenge was a race, 20 MPH would not cut it, and 20 miles is a lot shorter than 200 km.

I just love this silly motorcycle. It is totally impractical, but as a proof of engineering skill, it is so much more impressive than making a Hummer go down a dirt road.

Doesn't this contradict the autonomous criteria?

I've been thinking about that golf cart and day by day it seems a weaker option... if they only had a reseller here in San Diego that I could see and test it before I buy...

On the kid's ATV side, I had put some thoughts too. The 50 or 80cc seem perfect, but they don't have reverse, I'm not sure what you mean by putting an electric motor for reverse. The Grizzly 125 is the only I could find with built in reverse. I haven't looked at other offstream brands, so my answer may be there...

Cheers

Padu

"Mark Haase" wrote

The second one looks real cheesy (doesn't seem to have a suspension system), but I liked the first one a lot. I'll try to find more information about that model and company, thanks!

At first glance, it sounds more promising than an ATV. Seems to have reverse, easier to customize, strong enough motor and a heck of a price...

Thanks!

Padu

Yes, I remembered you making this suggestion a while ago. Seems promising, but correct me if I'm wrong, it doesn't seem to have a good suspension system. It seems it was made for good torque at very low speeds, isn't that right?

Thanks for the link though

Padu

"John Nagle"

No, I'm not underestimating... it's been almost one year I'm working on a small scale (R/C car scale) autonomous thing and it's already hard enough. I went to Primm to watch the GC, and that made me gain an special appreciation for this type of effort. I saw ghost rider in person (it's much smaller than I thought it was) and being a motorcyclist myself, I admire that they could get that thing moving by itself... What I think I could have been misunderstood is that for someone that is mechanically talented, building something like an offroad go-kart with off the shelf components may not be as difficult at first glance. In my case I would take ages to do it, as my handyman skills don't go past weekend around the house projects...

Cheers

Padu

I don't know how far that thing got this year, but last year as I recall it went about 10' and fell over. Clearly top-heavy. OTOH, an off-road motorcycle makes a nice light-weight and cheap platform that can go 50 MPH, and get 40 MPG.

Suggestion - add some "training wheels", or an outrigger, etc. Or better yet, turn it into a tricycle, like you see a lot of Harleys made into.

It went a lot farther. Cheap didn't seem to be much of a criteria in this event.

For years, the Baja 1000 was won overall by motorcycles. They are nimble, fast, accelerate quickly and

Harley trikes are so the bike doesn't fall over when the rider is too drunk to remember to put out their feet. :-)

Single track vehicles can avoid a lot of obsticals that two or three track vehicles hit and have to absorb.

I assume that the ghostrider folks did it for the challenge. There are lots of challenges in a robotic bike.

Actually, it didn't complete in the GCE.

I think they had this on this year's version - retractable "landing gear" that would fold up when the vehicle started into motion and then fold back down when stopped.

-Brian

I think I was on Crack perhaps, assuming there would be a chain that you could tsndem a motor to.

You might consider "small, fast, rough terrain...., chose any two." I'd save fast for last, as the platform is the easy part. I think it would handle a normal auto gravel road at full speed. Below are some links where lawn mowers and lawn tractors do go quite fast if you really need the speed.

"dan michaels" wrote in news: snipped-for-privacy@g44g2000cwa.googlegroups.com:

All the bike needed was a side car. Or a much better gyro so it could stand up right, balance on 2 wheels.

Put the wheels side by side like a segway and keep a low center of gravity and balance isn't much of a problem.

All motorcycles (and bicycles) have gyros, they are called wheels. They all balance well if they are moving. Multi-track, covered in another posting.