blis

I'd consider using a Ready to Run electric 1/8 truggy but it's hard to see the actual dimensions inside the model and how it can be mounted.

It would not be too difficult to extend the chassis if you disconnect the 4WD and leave the rear to drive 2WD and front to steer.


How heavy is it?

ThePanda

iTrader: (68)

Servo for sure.

If the picture is oriented, top is equivalent to the front of the car, you are going to get some funky steering geometry from the setup you have. I suggest keeping both links equal length, and have the same geometry left to right. Moving the steering links to the other side of the axle would be good to, as well as adding a little bit of Ackerman.

metalnut

iTrader: (36)

Thinking about this some more, your model is awsome enough for someone like Tekin or Castle to get behind a sponsorship deal. No joke. I'd definitely email both with that in mind.

cardboardlambo

Yea, I plan to make a nice aluminum square tubing frame, just a simple rectangle with a few cross beams.

cardboardlambo

Alright thank you for all the advice.
My route I'm probably going to take will be an aluminum frame.
build a steering mechanism which I know I can do, probably use a servo for steering then.
Drive will probably be just rear wheels and I know my ways around gearboxes and motors so I may buy an electric motor and a separate gear box so i can change ratios.

my final question (at least at the moment) is how much could I get to run off 12 volt DC. Servos and stuff like that.
I have powered with 12V batteries before and I'm wondering If I could run it all off of one. (The motors, servos, and control components)

metalnut

iTrader: (36)

Here is my thinking, and keep in mind this is crazy new to me but I like it

Looking at the Castle ESC, the sucker is rated at 33.6v, which is nuts, so 12v shouldn't be an issue. : http://www.castlecreations.com/products/mamba_xl2.html

Looking at the mother of all servos, this one is rated at 14.8v, producing an insane 1528oz of torque:
http://www.amain.com/Hitec-HS-1000SG...-Servo/p253479

However, most receivers are rated only up to 7.4v (2S lipo), so you'd probably have to have a BEC to regulate the voltage down for the receiver. Castle makes a very nice ones:http://www.castlecreations.com/products/ccbec.html

However, the one thing I can't comment on is the power behavior of a 12v battery vs, say, 3S (11.1v) or 4S (14.8v) lipo. Can a 12v car battery even power these electronics? DC is DC, but... I don't know. The one advantage lipos have is their light weight, which I think you'd want to take advantage of unless you're using a lightweight 12v car/motorcycle battery. That might be a good question for Castle.

ThePanda

iTrader: (68)

If you get to serious, think about among another body. Something like lexan or fiberglass. Cardboard will be destroyed in a crash. Both lexan and fiberglass will be repairable or replaceable in a crash, and start out being much more durable.

In my opinion This is getting crazy expensive now.

Dave H

Lead acid car batteries can deliver a lot of current, mostly because of their size (a fairly small lipo can start a car, there are videos). But they do have relatively high internal resistance, voltage varies a lot with higher loads, might result in more than ideal ripple current issues for the speed controller. At the very least use a deep discharge - marine type for better battery life. Although sufficiently sized lipos are likely a better choice, helps keep the weight down too.

Given the size involved with your project I suspect custom robot sites would be useful. For example ServoCity has a lot of building components that may be helpful, including gear reduction DC motors. Search for other robot sites for more building ideas and components.

asc6000

iTrader: (15)

Thats pretty cool. Looks like a fun winter project. You could consider buying something like this and using what you need and sell the leftovers. These can be had for $550 Ready To Run. Check the specs for wheelbase etc. It's a Ready To Run which means you just charge it and go.



Specifications
Motor TypeBrushless Motor 980KV
TransmissionSingle Speed
Drive System4 Wheel Drive
Length840mm
Width483mm
Height305mm
Wheelbase500mm
Ground Clearance25mm
Chassis Type4mm Aluminum 6061T6
ShocksAluminum Body Oil Filled
Speed ControlBrushless ESC 150A
BatteryQty. 2 - 11.1v 3900mAh LIPO Batteries & Charger included
Radio System2.4GHz Radio System

metalnut

iTrader: (36)

Although this could definitely get expensive, I think it would help if we knew the total weight of the Lambo, aluminum frame and all. Maybe you don't need a $400, maybe a $100 will have enough torque to get the job done?

cardboardlambo

I have had some experience in motors for robotics and I can get some pretty powerful motors and gearboxes for about $150. The only thing I think I need now is a servo for steering and a control system.

So I'm looking for:
1 servo to rotate on axle which will turn the wheels left or right
1 radio control system (this is my biggest issue)

ThePanda

iTrader: (68)

I would go with a setup that keeps both steering links on the same plane. Otherwise you could experience different bump steer settings left to right, especially when turning.

Also, look into how you will stop the car.1/2 scale is going to be very heavy when everything is together.

blis

+1

That's a better choice than a truggy.

cardboardlambo

I'm looking into a rack and pinion steering setup now that will make things a lot smoother.

And yea, stopping may be an issue but I'm not to worried.

ThoughtCriminal

iTrader: (2)

Just a n00b suggestion, but why dont get one of those electric kid cars? Grab a reciprocating saw and cut off everything but the frame. You can extend it to fit the length, and run a sevo to the speed control, and steering.

You can find those cars used at the flea markets/junk shops for under $20. Throw a 12v lawnmower battery in it, and it will cook right along.