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Old 12-10-2013
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Default Full Option IMA Integrated Motor Axle

Here are a couple of pics of the new back end I have done for the Mardave, which I am calling the IMA.



The concept is self-explanatory, and the results are very pleasing. The car drives as smooth as silk, and there is no mechanical noise from the lack of gears. The current set up is using a slightly low kv motor (750) which isn't drawing quite enough current as I can complete a race on about 800mAh on a 2-cell. As a result it lacks a bit of punch out of corners but is very comparable with 'normal' cars in straight line speed.
The other benefit is that the whole pod weighs just under half that of a standard plastic pod with 540 size motor and axle.
I am going to switch out the motor for a slightly bigger one (35mm can) to try to get a little more low end. Once that is proven, I will move on to stage 2 of the concept, which will be a customised rotor unit for the new motor with an integral diff.
Judging by the performance of this, it wouldn't surprise me to see all pan cars change to this type of drive before too long. Touring would benefit even more, with biased F/R drives for better cornering, but that would take some customised electronics in the ECSs to achieve.
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Old 26-10-2013
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IMA v2.0
Now using Aerodrive 3536 motor, 910kV.
This is a lot torquier, more powerful, and the fastest solid axle Mardave I've seen. Got second in the A final at this week's club meeting. Now got to make an integrated diff and it will be the complete package.

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Old 31-10-2013
JimboJames1972 JimboJames1972 is offline
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Really interesting idea here, always good to see others tinkering and thinking outside the box!

Good luck with it,

James
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Old 31-10-2013
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Thanks James, I really think this will be commonplace before too long. It's great to drive.
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Old 01-11-2013
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Do the race regulations allow this though Dave?

Part of the reason I stopped running 'Dave's at the club was that with a car "built to regs" I was totally out paced by the cars built to the club rules then, including your previous car.
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Old 01-11-2013
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Apart from 'anything goes' rules I doubt this car would satisfy the regs at any club. Certainly wouldn't at ours. My intention here was to see if the concept worked, which it does, so now I want to perfect it. I've missed enough weeks of our championship to not worry too much about not counting for points.
The rules at Gloucester are still 2S/21.5 or 1S/13.5 to count for points. People who want an easy life, and a cheaper car, go for 2S. People racing elsewhere too go for 1S. The racing is still great and I have to say, the most enjoyable I have had since starting at the club.
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Old 06-11-2013
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I just wanted to add I have been running with this concept car in recent weeks with a 2s supastox and it runs very smoothly and the current configuration is 100% competitive against the top GT12 runners at the club (GERCC - Gloucester).

It is slightly surreal to see it silently gliding around the track!

Good stuff Dave.
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Old 06-11-2013
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Quote:
Originally Posted by LongRat View Post
I really think this will be commonplace before too long. It's great to drive.

that I doubt!
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Old 06-11-2013
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Quote:
Originally Posted by mark christopher View Post
that I doubt!
I've heard that before - when I turned up at a track in Summer 2000 with 3 wires coming out of my motor.

With this layout the one thing that can't be escaped is the high efficiency. It is currently using roughly 3/4 of the energy to complete a race in a time faster than all but the very quickest GT12 cars at our club - compared to the exact same car running a 21.5T 2-pole motor. Properly designed, the suspension will work better as the unsprung weight is halved. These are major advantages and I am not saying my prototype has maximised any of this potential, but the potential is there to be taken and that isn't the case with a conventional geared transmission layout.
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Old 06-11-2013
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Don't some clubs still run mechanical speed controllers?
If that's the case I expect they will adopt this system in approx April 2213...
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Old 06-11-2013
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That's right. Then there are the clubs running tethered cars without radio control at all, they won't go for it either.
Personally I don't understand the MSC runners. Once you factor in a servo and the MSC itself, you could buy an ESC.
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Old 07-11-2013
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Very cool!
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Old 07-11-2013
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LR - how will we be able to compensate for tyre wear on this set-up, or change gear ratio to suit tighter or more open tracks? It's a clever use of the torque characteristics of a DC motor!
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Old 07-11-2013
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There is enough torque to spin up the wheels with this particular motor at low speeds, even with a top speed exceeding the rest of the cars on track by a good margin. I've been running the throttle to 80% so I don't have a crazy speed advantage. I think you might get away with setting up for the biggest track in the country and still have more than enough low end punch for the tightest track. That remains to be seen. Otherwise, rather than changing gearing it would be a case of changing stators. Not a major issue with these complete motors selling for under a tenner each.
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Old 19-11-2013
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I'm curious how you plan to do a diff on this one. Any chance to see an exploded view: all parts layed out in order before assembly?
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Old 19-11-2013
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Quote:
Originally Posted by mr. ed View Post
I'm curious how you plan to do a diff on this one. Any chance to see an exploded view: all parts layed out in order before assembly?
Here's a drawing of the assembly. I'm currently making the parts, hoping to have a running prototype by Friday. It involves making a new rotor with a row of balls built in. Because this style of motor has an external rotor, driven from the outside, it makes turning it into a 'motor diff unit' much simpler.

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Old 21-11-2013
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used to have an rc18b with an outrunner integrated into the centre shaft, also have a small drag rail with that setup, it works very well but you do need a higher rated speed control and good batteries because startup currents are VERY high. both are/were very smooth to drive, but very limited by the gearing, or lack of. not too bad onroad with foams i suppose because you can true your tyres to get suitable gearing. by the way, you want a really smooth mardave, try a keda 450h 3200kv outrunner, really good to drive!!
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Old 22-11-2013
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Love to see some pics dodgydiy.
But a Keda 3200 on a Mardave? That would be out of control. I doubt many speed controllers that could actually fit in a Mardave could handle those start up currents!
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Old 22-11-2013
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Great idea!...well done.....cant wait to see how it develops...
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  #20  
Old 24-11-2013
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Components for the motor diff unit.
-Motor stator
-303 stainless steel through shaft and ring carrier
-Modified 14-pole rotor
-Acetal ball cage
-Standard Mardave steel diff ring
-6082 aluminium differential hub
-Stainless end cap with stub axle
-End cap mounting screws

I just completed most of the parts. Test fit time.
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