Re: Sherman

[Frank Pittelli <frank-at-rctankcombat.com>]

Chrys,

Thanks for the compliments on the website and we're glad you found 
useful information there.  As to your drive system problem, the 18v 
motors should have sufficient power to move your 7Kg vehicle without 
much problem, because as you noted they are being used to drive much 
heavier vehicles.

My initial guess is that your batteries are not properly charged, or 
they are too old.  If you can try some different batteries that might 
point you in the right direction.

Another possibility is that the drill motors are trying to spin too fast 
and they are getting bogged down.  You might try adjusting the gear 
ratio to run with higher torque and less speed.  But, I suspect that the 
battery is the real problem.

I've CC'd your message to our mailing list so that others can chime in 
with their suggestions, especially our drill motor builders.  Everyone, 
Chrys is not on the list, so please remember to CC him on any response.

        Frank P.

CHRYSANTHOS KANELLOPOULOS wrote:

> Dear  Frank Pitelli,
>  
> We have not met in person but I take the liberty to contact you. I am an 
> architect (working for US AID funded projects in the Middle East) and my 
> hobby is of course, armoured vehicles.  My congratulations for your 
> website!  It is absolutely amazing and has all kind of information for 
> those who want to build a large R/C  vehicle!
>  
> I have built an Iron model of a Sherman chassis-Sexton/Priest/Kangaroo 
> tank in scale 1:16.  The iron plates - 2.5 mms thick- were drawn on 
> A-CAD, cut out on laser and then welded. The suspensions and wheels were 
> similarly drawn on A-CAD and made out of aluminium (to reduce weight) 7 
> mms thick. Tracks are readily available, inexpensive iron collars for 
> dogs- chockers!  - with idlers and everything. I have mounted two 
> cordless drill motors 18 Volts each.  I am hoping to have a fully 
> motorized -R/C STEEL model of the Kangaroo Sherman. I'll have to e-mail 
> you photos at some point if you accept attachments.
>  
> However, I am facing a problem: The vehicle is about 6.5-7 Kgrs heavy 
> and despite the two 18 V motors, it does not roll satisfactorily.  After 
> a few meters, or after the tank has to climb a small obstacle, the 
> motors just do not seem able to power the drills. They get exhausted so 
> fast! What would you advise me to do?  DO I need batteries of less Volts 
> but with more Amps? SHould I add batteries of 24 Volts each? 
>  
>  I can see in your website that Pat McCarthy's T-34 is motored with two 
> drill motors of only 14.4 Volts each and it looks HUGE relative to my 
> 1:16 Sherman.  Is it possible to know what the weight of Pat's T-34 is?
>  
> Another solution is to have the chassis and hull made again out of 
> aluminium.  That would reduce weight and would make the tank lighter by 
> 3 kgrs, and therefore more manageable.  I would then have to mount 
> everything (motors, gear, suspensions, idlers etc)  onto the new 
> Aluminium tank.  IT is all reversible.
>  
> Could you or anybody in your club help me with my project?
>  
> Thank you,
>  
> Chrys
>  
> AThens
>  
>