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Tamiya 70097 in RP5 Chassis Combination?


#1

Hi,

Can anyone please confirm the width of the Tamiya 70097 twin motor gear drive set and whether it will fit into
the RP5 chassis. Some mechanical mods are anticipated. The intention here is to add some speed to this chassis mainly.
It will be controlled by an SVP324 which should have plenty of juice.

This retro fit off course assumes/anticipates/involves:

  • removing the existing motors and gear drive altogether (still have to calculate the gear ratio which is an unknown)
  • removing the straight long 6xAA holder and replacing with a flatter battery pack equivalent(s)
  • replacing the tamiya motors with the pololu equivalent (lower current, higher voltage)
  • possibly having to alter the length of the hex 3mm shaft to make them fit (with/without a aluminium hub)
  • the outside rubber treads/wheels will be not altered in any way (all changes from the inside of the chassis)

Is it feasible or worth it? After research and advice from Jan, the metal micromesh HP motors dont look like they will make it,
especially appear the added payload of the batteries, pololu perspex plates, SVP board, wires, hex screws, nuts, etc.

Trying to keep the solution cheap if possible. Has one done this , or has attempted to?


#2

Hey, it’s me again.

I don’t think the Tamiya parts will really work, either. The final shaft sizes are different, and getting any other shaft to work with that wheel will probably be quite difficult. The Tamiya motors are also weaker than the ones already on the RP5, so overall you would be reducing your available power. If you want to go with the Tamiya gearboxes, I think the double gearbox is better than the twin-motor gearbox. You can use those with the following sprockets and corresponding tracks: pololu.com/catalog/product/224.

Ultimately, I think the RP5 is just not very well suited for redoing the drive train.

- Jan


#3

Hello,

Have you see the Tamiya Track and Wheel Set? Maybe that could work for you.

- Ryan


#4

Thank you Jan and Ryan,

It seems the thought making this platform go faster with minimal cost is not achievable with the RP5.

The problem I am having, is that RP5 tracks and gear drive are not balanced, and the unit seems to
always drift to one side. I have corrected that by using the aceclerometer to detect X axis deviation
and adjust motors accordingly. It works. However, it consumes some processor power(PID loop).

I greased the gears, adjusted the tightness of the screws and made similar alignments to balance it as much
as possible in the mechanical sense. I can live with it for the time being while I brush up on my C and algorithms programming.

Ultimately, however, I am looking at upgrading the platform.

So the next question, can I drive to two 12 Volt motors with the Orangutan SVP (the 2A continuous current is there)??

Lynxmotion has a TRI-TRACK (Johnny Five type ) chassis with a 50:1 gear ratio. Only problem is that the motors are 12 volt motors.
Can the 7.2V supply drive a 12 volt motors effectively ?? I dont see it as a problem, however, a second opinion is always appreciated.

Regards,
Carl


Changing Motor
#5

You can usually drive a 12V motor at 7.2V, but it will be slower. The SVP can go to 13.5 V, which is slightly below what a well-charged 12V battery is, but it should be able to handle the 12V battery. You could also do something like an 8-cell NiMH pack to get a nominal 9.6V and around 11V charged.

In general, you’re not going to get something with differential drive to go very straight without some kind of feedback-based control. It’s cool that your gyro approach worked!

- Jan