John_Mac

I have an old Radio Shack RC ATV that I stripped down, converted to Spektrum Tx/Rx which I use as a development platform to test autopilot hardware using gyros/accelerometers/GPS/Video/OSD and microprocessors. It is meant to run in rough terrain. A couple problems I have is that the rear differential has a busted gear and can't find replacement parts, so running with front wheel drive only, and it is very difficult to get its speed down due to the gear ratio. I run a PIC microprocessor to issue PWM pulses to an H Bridge that drives the motor to slow it down, but its not a good solution.

My question is, can anyone point me to a better platform? Here are some of my needs:

4WD, Off Road capable suitable for rough terrain, able to run at faily low speeds, electric powered, I have the Tx/Rx so only need steering servo and ESC/BEC for drive. I will probably strip it down to bare chassis, so not concerned about fancy bodies and looks. Ability to get spare parts.

Anyway, any suggestions are appreciated.

John

maybelater29

My Feedback: (1)

How slow and any minimal dimensions?

traxxaspede

what about a crawler like the AX10?

maybelater29

My Feedback: (1)

I was thinking about that..I just didn't know how slow he needed to go and also how much exra room he needed for mounting....Something like a Summit might also work....2 speed with 70:1 and 25:1 ratios....you can have the best of both worlds and have more room for mounting equipment.

John_Mac

Yeah I should have been more specific there....

Something around walking speed, but would be nice if it could be (remotely) shifted down to crawling in really rough terrain

The current platform is about 22" front to back...that size or a little bigger is good.


Oh yea...and I don't need a second mortgage to buy it!

Spiro

woops! Didn't mean to post.

Access

Summit or a super-class crawler, are you building superstructure onto the chassis or you just want the size for the size?
The problem you are going to have with a lot of the crawlers out there is that the chassis itself isn't really that large, if you are trying to mount something big onto the chassis there's just not going to be enough to mount it to. If you're doing this go with a summit or something similar. As long as you are not doing extreme rock crawling the summit will do most outdoor terrains fine.

maybelater29

My Feedback: (1)

+1 The downfall to the crawler is space....the Summit has enough room on the chassis to mount extra stuff..

[link=http://www.bigsquidrc.com/pictures/ihobby2008/full/ihobby_34.jpg]topless Summit[/link]

[link=http://www.rcslot.com/mm5/graphics/00000001/AXI90001.jpg]topless crawler[/link]

ESForeman450

how bout a good used emaxx, maybe one with the 2speed and gear it down a tad. or a wheely king with a chassis flip and a high turn mtor if it was too fast with the job with the stock motor. them maybe a good cheaper way to go. just tryin think of cheap ideas.

John_Mac

Here is a picture of my current platform....like I said it is a stripped down chassis of a cheapo Radio Shack ATV. The pic just has some prototype electronics on it, I would plan to use most of the top part of the chassis with other electronics and sensors...so yea I need some space. Actually if this thing just ran slower and didn't have a broken back diff, it would be an OK setup.

I just hate to buy a cheapo Radio Shack and find I can't get replacement parts. So an expensive crawler isn't necessary, just big tires and 4WD, slow and spare parts. Only good thing is that it was cheap and I can throw out all the low end Tx/Rx, servos and electronics and use my good stuff.

Spiro

I recommend trying to find something used in decent shape once you have decided on the platform. No reason to pay new prices for what you are wanting to do

Spiro

hands without shadows

Would you be comfortable building the chassis yourself to your specs? If yes look into to some solid axles like crawlers use. To maximize space look into motor on axle axles like the Tamiya Clodbuster uses. Each axle has its own motor built into it and each axle has its own servo.

UF DUB

for large size, durability, and cheap parts, why not look at an HPI Savage? It would be comparable in size to what you have and be very durable and cheap. also, it could be converted to electric (or just buy the flux...) and be geared very low if need be. I hesitate with crawlers because they are quite slow and no room and the summit is very expensive for what you want.

maybelater29

My Feedback: (1)

Crawlers go at or just above walking speed...the speed he indicated...also the FLUX are you kidding me, you say the Summit is to much yet suggest a BL 60mph $650 truck...I know you might just be an HPI fanboy but how can you call one thing to expensive then suggest something that is $200 more and doesn't have the ability to do what the OP intends to do...

aramid

I can't think of anything better for your purposes than a used Traxxas E-Maxx. They can be had cheaply, and the electronics are arranged in such a way that you should have plenty of space to attach mounts for your own components. Take a look at this image of one to see what I'm talking about. And if you get the truck and find it's much faster than you need, you could probably switch to a single-motor/single-battery setup to free up some space and weight, and still get 5-10 MPH out of it.

UF DUB

I do not own a Savage, nor am I a fanboy but I do know that it is a reliable, cheap rig (one of the things he was looking for). Somone else suggested a Summit, so I simply pointed out that a Flux would be larger and probably stronger.

A large crawler is a tough rig and does travel at the speed he desires (walking speed), but there ISN'T MUCH ROOM for all the electronics controller, sensors, video, processing computers, and such that he wants to run. Space on a crawler is always limited.

A traxxas emaxx would be a good alternative; it does have room and parts are cheap. Also, you could look into a used truggy. It would be faster, but could be converted to electric and would have lots of room and be very tough.

There are lots of options, just look around and others will have good ideas as well.

hands without shadows

Crawlers go that speed and have that little room because we want them that way and build them that way. It would be easier for me to build a crawler with a little extra speed and a chassis with room for more electronics than it would be for me to build a balls out crawler.

maybelater29

My Feedback: (1)

I'm not saying an e-savge wouldn't be a good platform but a Flux is overkill and way to expensive...I came off kind of bad earlier but saying one thing is too expensive and than turn around and suggest something more expensive and less in line with the needs (the flux would need to be modded to get rid of what you are paying all the extra money for) was weird.

ESForeman450

i still think a used e-maxx would be the cheapest way for the man. but if he wasnts a new truck for his use. e-savage would be about the best deal for him. because you can get it rtr with charger and batterys for something like $330. i wish thats the truck i got.

John_Mac

Thanks for all the suggestions...I will keep an eye on ebay to look for a good used platform. RTR is probably a waste since I will be replacing the Tx/Rx...unless it it really cheap. Wish I could find a new gear for the rear diff on my present platform