George Jure

Hello Again

First I would like to thank the members here for their past help. To recap, I am converting a 1/6 static WWII replica car into it`s 4wd r.c version using the suspension, drive train of a RC18T. What I need to understand is that I know the motor 280 brushed motor has a 2mm shaft and I have found a few on ebay. Their specs are confusing, they say it runs on 3v how much does the average motor run on in an unmodified RC18T? Also about the pinion gear, found a few again on ebay for 2mm shaft BUT they are called 12T - 15T which should I go for since I want to slow the motor RPM as much as possible? Does the pinion gear number reflect on the RPM, the higher the pinion number then the slower the RPM from the motor through the pinion to the drive shaft gear?

Also I want to add that this setup is direct drive and there are NO belts or plans to use belts.

So PLEASE if you can, explain to me the pinion gear relationship to motor and drive gear setup so that I can get a basic as slow as possible RPM motor with a slow pinion gear to drive my future setup.

Thanks Again for the Information.

George

phmaximus

the gears dont affect the motors RPM. load and power affect that.

all the pinion gear does is change the gear ratio, to work out the gear ratio its pinion devided by the spur times the diff ratio.

Allso keep in mind brushed motors have no torque at low RPM the volts sent to the motor is controlled by the ESC.

power is volts times amps, if u drop the volts u will loose power.


Personally I dont think this will work. there is no way the RC18 has the right gear ratio for the speeds u want and the motors u are looking at wont help either.

MY TIP TO YOU

get ur maths right.
how fast did u want it?
whats the wheel circumference?
whats the diff gears ratio?
whats the RPM of the motors u are looking at?

once u know that with some simple maths u should be able to work out the required gear ratio.

Like I said in the thread u created just the otherday, im doubtfull u will get the ratio u need and will have to make a GRU.

Are u sure u want to use the RC18t??? why not use something with solid axles for a more scale look?

George Jure

Hi phmaximus

Thanks for the lessons and tips. The reason why I picked the RC18T to be the source of the parts for my scratch build is because from what I could see in my research, the real scout car had similar looking suspension. Also I got the RC18T at a real good cheap price. I would like to have gone with a ready made axial BUT I could`nt find the pair that would fit my 1/6 car and be cheap enough to be used as an experimentor use. When I did the math, two axials would be on average $140.00 Canadian PLUS the other drive gear parts and suspension, very costly.

So I will try to go ahead with your math tips and my other parts for this build.

Thanks Again for Your help. IF this turns out to be a decent car, I will post the build, if I learn how to do it.

George

phmaximus

know worries....

we are here to help, what have u done so far?

How well does the RC18 match up??? have u got any pics of it next to the body of this scout car? is it a M3 US scout car?

Let me do the maths for ya,,, lets start with whats the diameter of the wheels and how fast did u want it to go?

hang on, does the kit have suitable wheels? the tamiya might be close

George Jure

Hi again phmaximus

Thanks for your offer to help. First, you might want to have some headache medicine ready, I can give people headaches with the questions and how little I know.

That said, here goes:

1. My scout car is a 1/6 Ultimate Soldier WWII German Schwimwaggon, that was a 4wd car/boat combo. It drove on land and could cross slow rivers with use of a rear propellor. The tire dia. is 4 1/4
inches ( 10.6cm approx. ) it`s width is 1 1/4 inch ( 3.2 cm approx. ).

2. I have a source RC18T chassis, it has NO wheels, hubs. I plan on making a hub to allow me to use the plastic one piece wheels that came with the schwimmwaggon, for future I call it a schwim o.k ?

3. The original`s speed is unknown to me but it was the 4 cyclinder engine that later became the VW Bug, if you are familiar with that one? So it is NOT a racer, it was meant to scout for enemy, get
away as fast as possible.

4. I know I will have to lengthen the RC18T main drive shaft, luckily I have a metal lathe, as well as the dog bones. That is not a large worry for me.

5. I found on ebay a Mabuchi motor RE - 280 RA - 76067A it looks to be the type that I need, according to the RC18T manual and its cheap! I can`t fnd out it`s speed (RPM) though. I will be using a
small ESC with reverse to run the drive motor as well as a second esc for the propellor drive.

6. Pictures for now, I can`t do, my camera is out with a relative and when she comes back I can start to put together pictures as well.

7. Just to let you know, I have health issues that will cause me delays in this project and that means I can ask alot of questions BUT it will take a long time for me to show results here.

Thanks Again for your offer to help me with this. If I missed something please let me know.

George

phmaximus

cool, what a intresting little car.
4-cyl. boxer, air cooled
1,131 cc, 25 hp @ 3,000 rpm
4 speed manual.
2wd/4wd in 1st gear (some had 4wd in reverse)
portal gear rear hubs
50mph land
6mph water

ok lets get the speed worked out, 10.6cm wheels
so that a 33.3cm Circumference.
Now because its top speed is 50mph, we want urs to do about 1/6 of that maby slightly under so 8 mph isabout the max u want ur model to go. so 21480 (centimetres per minute) = 8.00823193 mph so we want the wheels spinning at 645.045045045045rpm to get around 8mph

ok cool now we have someware to start, now the RC18T has a internail gear ratio of 2.5:1 (645.045045045045rpm*2=1612.612612612613rpm)
To get the scale speed we need the spur gear spining at 1612rpm the biggest Spur i can find is 60t and Losi have a 9t pinion (Team Losi LOSB1260)
that would make a ratio of 6.666666666666667 meaning u would need the motor to be pulling 10750.75075075075rpm max

now we just need to find a motor with 8,000-10,000rpm

George Jure

Hello phmaximus

My God the math involved. It was easier taking my College Elecronics Math classes!

So I need a motor that has an RPM of upto 10k rpm max. and a pinion gear of 9t, could 10t be acceptable? Remember I am NOT much of stickler for scale, close enough is good enough by me.

Thanks Again for Your Help. Now off to ebay.

George

phmaximus

10t would be fine. but im having trobble finding a motor thats 380 size that has a low RPM. If u mod the motor mount for a 540size motor the smallest pinion u can run would be 47 tooth pinion that would make the spur topinion gear ratio 1.276595744680851 meaning u would nee a motor to pull 2058.665888441634RPM max, but we can over come this with a Tamiya planetary gearbox, it can do ratios of 4:1 5:1 16:1 20:1 25:1 80:1 100:1 400:1
one of those ratios would do the trick, but hard to tell what one with out the motors RPM.

phmaximus

The problem is going to be room. might be worth looking into these....



Its a tamiya CC01 rear axle, would be so much eayser to connect the tamiya gear set up to

George Jure

Hello Again

Thanks for the info. but I am going to go with the original plan of modding the RC18T parts I need. Also I found a RE280RA motor on ebay. I also found the pinion gear you listed as well, it comes in a pack with others though. I only want the one, will continue to lok for it.

Well for now I`m going to the Hospital for another proceedure, nothing serious But it delays my work on this project during the healing. Physical work no but I can still plan and search on line.

Thanks Again for Your Help.

George

phmaximus

Good luck, we will here from u after?