TheGreatMoo

I'm new to this part of the forum. Normally I'm over at the warships, or tanks, but I'm not new to RC. I loved the Mako in Mass Effect (Xbox 360 game) so I'm going to make not a scale model of it but the general shape and design of it. This is what I have so far in 3d. The wheels diameter is going to be 4.5 inches, 6 wheels, each powered by its own motor. I'm doing that to eliminate dog bones and differentials is that a bad idea? If all motors are the same they should be all spinning at the same speeds running off the same battery shouldn't they? How do I hook 6 motors up to a speed controller? would 2 speed controllers be enough, or would I need 6? I plan to run it on 6 volts off 1 or 2 sla's 14 ampers

The Hedgehog

If the wheels are different sizes there will be a difference in speed between wheels, like a gearing change.

electricrcdude

how are you going to hook up six motors to one battery pack? battery should drain pretty fast. like the idea though.

TheGreatMoo

well they will be running on around 14 amps im sure they wont draw much more then 1-2 amps each motor.

wheres a good place to get ball joints? I need fairly strong ones 3 for each wheel, one for the control arm and 2 for the suspension

hands without shadows

In a scenario like this you would want all the motors wired in parallel to the ESC, meaing all the motor positives go to the ESC positive and all the motor negatives go to the ESC negative. Since you will have 6 motor you will probably be using 280 motors? If you are a 15t ESC should get it done, but I'm not sure on that.

On the ball joints, Revo rod ends threaded with 8-32 all thread and sleeved with 1/4" brake line make for a beefy control rod. Maxx rod ends will work with 6-32 and 3/16" brakeline if thats the size you want. If you want somethinng bigger or smaller let me know and I'll find it.

What program are you using to model?

TheGreatMoo

I made the 3d model in 3ds Max, I'm not looking for what to use for the control arm, but I'm looking for a cheap way to hook up the suspension arms to the wheel hub for strong support, I'd rather buy some like ball sockets, rather then making my own

as for the speed controllers, I need at least to because the Mako in the game combined steering and tank like control at low or no speeds. I cant have all the motors connected the same way because then each wheel would need different gearing inside

hands without shadows

Check [link=http://www.mcmaster.com/]this page[/link] for rod ends.

If all the wheels are the same size why do they need different gearing?

Slo-V Flyer

He's talking about steering I think. He needs at least 2 ESCs and a way to make the truck steer by changing the ESC's throttle on one side. However, I have no idea about a device that would let you mix the 2 ESCs together and make them steer too, but I guess r/c tanks do that some how, so you might wanna check that out.

TheGreatMoo

they have a few good speed controls over at the robot marketplace, I use one in my battle ship. but im not sure if they can handle more then 1 or 2 motors let alone 6.

That link is EXTREAMLY helpful thank you alot, includes drawings so i can easily make them in 3d to see if they work fit properly.

My brother works at a place where they fix up tools, he will be able to help me make the prototypes to use to make molds off of. does anyone know any good methods for producing molds? I was thinking to make rubber or rubber-like molds then use some kind of plastic or resin to make the parts.

One other thing is in the design in my first post the only thing keeping debris out from the internal gears is that one pink disk, how do you think i can like seal the gap in between that and the wheel so nothing goes inside?

TheGreatMoo

Here's what I got so far, I found some ball joints that will work. Still need to find a cheap set of springs and dampers. Working on the control arms right now.

hands without shadows

Craft stores like Michaels carry mold builders latex, casting resin, and catalyst. The latex paints onto objects and can be dried with a hairdryer or overnight. As many layers as you want can be added to make the mold as thick as you want. The mold then peels of the object and can be filed with the resin and catalyst to produce a clear plastic part. This method of casting does not require any risers but it does require a small gate and runner, as well as cores. You will have to hand finish the gate area when the casting is complete but you will not have any parting lines. I wouldn't expect tolerances to be great with this process.....

You could alternatively make most of the frame out of sheet stock with a jigsaw, drill, and sandpaper. Delrin (acetate) is a strong plastic that machines easily and would ge great to use for this.

TheGreatMoo

A friend of mine in the model warship club recommended to use this stuff. Looks pretty good, and fairly cheap, on the site it shows they used that resin to make parts for 1/16th rc tanks, but im not sure if it would stand up in this, what do you guys think? Also they have a rubber resin, perfect for making the rubber tires for this!

[link=http://www.alumilite.com/checkout/index.php?cPath=23_34&osCsid=8d69d1baff52a99d1b955c042ec59b64]http://www.alumilite.com/checkout/index.php?cPath=23_34&osCsid=8d69d1baff52a99d1b955c042ec59b64[/link]
[link=http://www.alumilite.com/checkout/product_info.php?cPath=22_29&products_id=83&osCsid=89b865b8203976e093a81ff3d86e47cb]http://www.alumilite.com/checkout/product_info.php?cPath=22_29&products_id=83&osCsid=89b865b8203976e093a81ff3d86e47cb[/link]
[link=http://www.alumilite.com/checkout/product_info.php?cPath=22_33&products_id=88&osCsid=89b865b8203976e093a81ff3d86e47cb]http://www.alumilite.com/checkout/product_info.php?cPath=22_33&products_id=88&osCsid=89b865b8203976e093a81ff3d86e47cb[/link]

TheGreatMoo

Well this is stupid, I just called the place I was planning on ordering the gears from and its like $2000 just for one gear... a 3 inch diameter internal gear made out of plastic is $2000....................... from www.rushgears.com I was going to order from them because they had 3d models of every gear they sell so i used those in this 3d model of the car, anyone know where to find cheap gears? I a 24 pitch 72 teeth internal gear, and a 32 pitch 34 teeth gear. the rest I can get at like towerhobbies. but I cant seem to find those anywhere else!

hands without shadows

I searched around some but did not find anything. The closest I could find to a 32p 34t was a 32p 32t on the same site that has the rod ends.

Can internal gears be made with a standard gear cutter? It may be cheaper to have them machined in a small shop somewhere.

nitrorcjunkie

Looking at your model, you could use monster truck a-arms, from a T-Maxx or a Monster GT. Lots of aluminum ones in the aftermarket.Shocks would be a snap with those. Consider direct driving the wheels, with an outrunner type motor system. Check the electric flying section at Tower. There's even geared systems, planetary and whatnot.

TheGreatMoo

I just got some Alumilite a few days ago made a test mold and a few parts and this stuff ROCKS!! the gears that came out of the mold are very strong and look like they would hold up in the gearboxes for this car, id recommend this to use to make like spare parts its very good. heres a pic of the original, mold and parts i made with it, the pink mold has to sit over night but the resin for the parts dries right in front of you, a 5 min demold time! very quick and cool

hands without shadows

Those gears came out very nice indeed. Looks like you may be onto something with this Alumilite stuff.

wookie_racer

My Feedback: (8)

yeh i have used alumilite before. it is nice but i dont think it will hold up to high power apps. but for this it should work good.

TheGreatMoo

I redesigned the whole gear box heres some pics. I was at a friends cutting out some parts I printed to scale out to make molds and they looked like **** lol, I come home and my mom bought me a drill press and a scroll saw!!!!!!!!!! so I re-cut everything and they are like EXACT that scrolling saw blades like 1/32 in its insane. these tools PWN, they were from mills fleet farm 100$ a piece very good quality to. I got the molds curing right now ill post some pics of them when i make some copies tomorrow

o yea quick question, is it possible to connect 3 servos to one channel like by a y harness, or do i need somthing else?

hands without shadows

Keep in mind that the front servo needs to be reversed. You can reverse the servo internally by [link=http://www.rccrawler.com/forum/showthread.php?t=53956&highlight=step+servo]switching a few wires[/link], you could buy [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXANF2&P=ML]a reversing Y harness[/link], rethink your design, or buy servos from different companies. I don't know off the top of my head which companies turn different ways but I can find out if you want.

Once you have the reversing worked out you need to connect all the servos to one servo plug. All the whites go together, all the blacks go together, and all the reds go together. You could buy a harness (more likely you will need to buy two) or make one yourself that fits your vehicle perfectly.

You can compensate for the middle axle's Ackerman by moving the steering links up the servo saver towards the output shaft.

TheGreatMoo

heres how far i got today, pics of the 3d model and the real one, and pics of the molds and plugs

TheGreatMoo

I have a prototype of the gearbox and wheel made out. Since the motors are in the wheels I'm going to need some more beefy servos because of the weight. I don't really want to buy them Id rather make my own but I'm not sure if you can just simply hook a electric motor up to a servo channel. I want to build a gearbox with a worm gear for steering, how would I make the motor driving that return to the center when you let go of the steering wheel? Also if I did that how would I make it stop at a certain spot when I have the steering wheel all the way over to one side?

Heres some pics of the gearbox so far (no gears yet) and the wheel. One question about that also. The diameter of the wheel hub is 5 inches and the rubber wheels I have are the same so there will be no cushion. Should I get rubber tires that have cusion such as a 6-7 inch diameter wheel? or can I still use these rubber wheels I have somehow?

Thanks

hands without shadows

A servo consists of a potentiometer, motor, geartrain, and electronics. The potentiometer is attached directly to the output shaft and changes resistance as the output moves, allowing the electronics to determine position and power the motor. You have the skills to build your own geartrain, use your own motor, and add your own potentiometer (you can use the stock one or any other potentiometer with the same value). The problem is that a servo's pcb (printed circuit board) is built to control a small motor and it cannot handle the amps a larger motor pulls. The fix is to remove the stock motor, replace it with a suitable h-bridge, and add your own motor. Adding an h-bridge will also allow you to use power from the main battery pack. [link=http://www.webcom.com/sknkwrks/mowers.htm]Here[/link] is a writeup on the process. If you tell us what size motor you plan on using we can give you an amp value to aim for.

TheGreatMoo

the motor is still open as to what im going to use. I plan to have 1 steering unit total, and the output will be a 1/4 in shaft running the length off the car and servo horns or something similar attached in 3 spots, and the gearbox will have a worm gear in it so its very strong. I'm working it out in the 3d program now and ill show you what im talking about, but just like a standard sized motor like you find in walmart rc cars etc is all im looking for, since it will be worm geard down it doesnt have to be terribly strong.

I'm not sure if I would be able to build anything like that, is there anywhere to buy something already made for this?

Thanks for the help so far!

RC_Basher20

My Feedback: (4)

this is comming out very well, wont those tires burn out?