Full Option IMA Integrated Motor Axle

[LongRat]

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

https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-prn2/q71/s720x720/1379554_10153290012425167_355482142_n.jpg

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.

[LongRat]

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.

https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-ash3/q71/s720x720/1381529_10153336864350167_433101364_n.jpg

[JimboJames1972]

Really interesting idea here, always good to see others tinkering and thinking outside the box!

Good luck with it,

James

[LongRat]

Thanks James, I really think this will be commonplace before too long. It's great to drive.

[RogerM]

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.

[LongRat]

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.

[grayslick]

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.

[mark christopher]

I really think this will be commonplace before too long. It's great to drive.


that I doubt!

[LongRat]

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.

[Col]

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...

[LongRat]

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.

[westie]

Very cool!

[SlowOne]

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!

[LongRat]

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.

[mr. ed]

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?

[LongRat]

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.

https://scontent-b-lhr.xx.fbcdn.net/hphotos-prn2/q71/s720x720/1451477_10153454049960167_357576593_n.jpg

[dodgydiy]

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!!

[LongRat]

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!

[simon]

Great idea!...well done.....cant wait to see how it develops...:thumbsup:

[LongRat]

https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-ash4/q75/s720x720/1450172_10153472137785167_1583212582_n.jpg

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.

[mark christopher]

so its not going to be something you can buy off the shelf?

[LongRat]

That depends on the success, or otherwise, of the concept.

[mr. ed]

What are these motors normally used in; boats, planes, heli's?

I could very well imagine one of these go into a shaft-driven touringcar; just in front of a pair of saddle-packs.

[LongRat]

These motors are used in multi-rotor helicopters and planes. The ability to swing huge propellers without a gearbox is a big benefit. Price is lower, reliability is higher and efficiency is greater. The same benefits can all be realised in wheel driven vehicles.
On top of that, because the magnets are rotating in the open air and are mounted on a huge annular steel heat sink, they don't get as hot, so you can push these motors a lot harder than an 'inrunner' conventional car motor. So a smaller motor will give more power.

In a touring car the inline shaft concept would of course work. In my opinion, the real benefits would be realised only without the transmission shaft, with a motor in each bulkhead and no mechanical transmission at all. Then you can use electric overdrive, on-demand oversteer and all the other things that allow the car balance to be constantly fine tuned for the best performance in all situations. And you can put all your gear right where you want in the chassis - dead in the centre.

[SlowOne]

It will need to be in the shaft - only one drive motor allowed in Touring Cars!

[gerbil]

Would this concept work in a v 10 I've got sitting here just fancy having a play with it

[LongRat]

Gerbil - yes.
SlowOne - there are far bigger obstacles than the single motor rule. For a start even one of these motors is not of BRCA legal construction in the first place.

[simon]

If,say you were running a 6.5T motor in a car,what would be the equivalent in one of these outrunner motors?

[mark christopher]

Gerbil - yes.
SlowOne - there are far bigger obstacles than the single motor rule. For a start even one of these motors is not of BRCA legal construction in the first place.

Which is going to make it just as hard to be accepted by the 12th section for GT use!

[mr. ed]

These motors are used in multi-rotor helicopters and planes...
In a touring car the inline shaft concept would of course work. In my opinion, the real benefits would be realised only without the transmission shaft, with a motor in each bulkhead and no mechanical transmission at all. ...

Thanks for your reply. I see your point, but with the larger diameter wheels keeping the reduction of the shaft to the diff seems like a good compromise. And keeping the diff action in is probably good too
The bulkheads are a bit narrow also, and twin moters with the assorted ESC = getting expensive

Unfortunately I don't have a shaftdriven touring car anymore to give it a try.

one more question: am I right in thinking you get a stronger effect of the drag brake adjustment without the reduction on your GT12?

[SlowOne]

Which is going to make it just as hard to be accepted by the 12th section for GT use!My point too. For National racing it is a totally pointless exercise. As an idea incorporating some clever concepts and a good design, I can't wait to see the full thing completed and a report on how it goes. :thumbsup:

[LongRat]

Mr. Ed, the drive torque increase in this style of motor is also seen in the back EMF and drag braking effect. You don't get a stronger drag feel at the wheels, it feels much the same as a normal set up in that respect.
Believe me, choose the right motor and there would be more than enough torque to light up the tyres on a touring car without any gearing needed. But, you would certainly need the integrated diff as that's really important for the touring car. As you say, making that whole assembly narrow enough, and developing the appropriate drive electronics would be real challenges - but surely a lot of fun too.

Which is going to make it just as hard to be accepted by the 12th section for GT use!

For God's sake Mark, can't you stop going on about the regulations and the '12th section'? This is about experimentation and trying different ideas, not winning world championships or even competing in national events. Someday, maybe this kind of thing will be popular and allowed for racing. I think we all know it isn't right now.

[mark christopher]

- there are far bigger obstacles than the single motor rule. For a start even one of these motors is not of BRCA legal construction in the first place.

From the man who wants nothing said about regs, but who posts it in mardave thread .....:thumbdown:

[Chequered Flag Racing]

For God's sake Mark, can't you stop going on about the regulations and the '12th section'?

:thumbsup: :D




This is about experimentation and trying different ideas, not winning world championships or even competing in national events. Someday, maybe this kind of thing will be popular and allowed for racing. I think we all know it isn't right now.

:thumbsup:

[mark christopher]

:thumbsup: :D



:thumbsup:
:rolleyes::rolleyes::rolleyes::rolleyes::bored:

[morpheus2010]

Given that Brushless motors - Lipo Batteries -2.4GHz Tx have only been adopted in recent years, I must applaud the efforts and skilled endeavours of LongRat :thumbsup:

Proof of Concept is original thinking carried into practice where it could be taken up by manufacturers that would drive prices down in volume production. :wub

Another gain is no frictional losses via gears - the possibilities are there for IMA

GT12 is a low cost class that has a good following and innovation properly developed has a place in RC. It may take time for IMA to be accepted so keep up the good work LongRat and keep us posted :cool:

[LongRat]

Thanks for the encouragement.
There is a problem with the current design of the motor-diff unit, in that there is insufficient support for the rear of the rotating can. I have a couple of things to try to overcome this... I will update the thread once this is done. Here is a picture of the finished unit assembled.

http://i43.tinypic.com/2z9bf9h.jpg

[mr. ed]

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.

https://scontent-b-lhr.xx.fbcdn.net/hphotos-prn2/q71/s720x720/1451477_10153454049960167_357576593_n.jpg

I must admit I still don't quiet get how this will perform as a diff.
As I see it the left outdrive will have the RPM of the motor, while the right outdrive can go faster (in a turn to the left) or slower (in a turn to the right).
Sofar all good, but driving a straight line will get difficult unless the diff is set tight enough for the right wheel to keep the same RPM.
Could be my lack of insight on how the out-runner motor functions.

I do much admire your very good finish of those mechanical parts.

[LongRat]

The outer can of the motor turns, which is directly connected to the ball carrier. This is the part that would normally be the spur gear in a conventional set up. So the motor drives the balls, not either of the outdrives. The outdrives are free to rotate separately from each other and from the motor can and ball carrier.
Think of it just like a conventional Mardave or pan car ball diff, but the spur gear is the end bell of an independently spinning motor.

I think I might have a solution to my current problem, some components are on order and I will update the thread when they turn up and I have made a couple more parts. Should be interesting...

[mr. ed]

Got it, thanks for explaining that.
Looking at it now, I think the high torque comes mainly from the 14-pole design, and not as much from the out-runner principle, right?

Would it be more or-less correct ot say that you could go from a reduction of 1:R for a 3-pole motor, to a reduction 14:3R?

Do you need a different ESC for these 14-pole motors?
You mentioned the AMP ratings, but anything else? Frequency perhaps?

[LongRat]

I don't feel I can properly answer all of those questions, but here is my take on it.

1. The outrunner principle moves the force application point significantly away from the rotating axis. While I haven't calculated the relative effect of this against the increased pole-count, I suspect this is just as strong a contributing factor.

2. These motors have 12 stator poles and 14 rotor poles. 540-size car motors generally have 2 rotor poles and 3 stator poles. The average spacing of a live stator pole to a permanent magnet is FAR closer in the outrunner design.

3. In order to make an inrunner with the same pole count, it would have to be physically much larger than an outrunner of the same power, so I don't think they are really directly comparable.

4. Every sensorless ESC I have tried with outrunner motors runs them. Currently I am using a Hobbywing Extreme Stock and the starting smoothness and speed control is just as good as any sensor-based system I have used on normal car motors. There is likely to be a stronger back-EMF signal at low rotating speeds than you get from a conventional system, leading to improved sensorless performance.
As an idea of the starting performance, I can grip one of these motrors quite tightly in my fist and smoothly throttle up, and it just starts rotating without any trouble.

5. Switching frequency does need to be higher for outrunner motors, but it is still way within the capability of all modern ESCs.

[morpheus2010]

I would have thought the out runner motor would have High Torque because of the multiple coil energising coupled with the effectively large rotor diameter.

That being said the rotor mass is also quite large albeit rotating at a far lower speed that your typical 540 rotor. Wonder if gyroscope type forces come in to play? Could be a stabilising force helping keeping the wheels pinned to the track.

Crude check could be spin up the motor on the axle set up and try to rotate the chassis (hand held) at 90 degrees to the axle line, you could feel any torsion/twisting effect if its significant.

Just food for thought :D

[LongRat]

Interesting idea about the gyro forces - I'll spin it up and give it a test. One thing that is different is the torque reaction force. This will have an anti-squat effect on the pod.

[mr. ed]

The more I read about them the more I'm inclined to get one for experimenting.
For m purpose though I'd like to have one with a 5mm mm axle, and I did find some... but alll 3S or higher.
One had a chart showing performance for different voltages and showed far from optimal for the voltage range of a 2S pack.
Is there anything you could recommend with a 5mm diameter axle?

[LongRat]

The way I specified the motors and decided what to get:

1. I wanted RPM to be similar to a geared 21.5T car motor. This is roughly 2:1 on a 1800kv motor. So that puts the kv requirement at 900kv.

2. I decided what power I thought would be needed, and looked for motors sized to be able to develop that power - that also had the required kv.

Most small outrunner motors suitable for these cars will be designed to run on 3S. In aircraft, that would give the best compromise of weight and efficiency while still giving reasonably high voltage - always the best route to efficiency and therefore performance. That doesn't mean that you can't run them on lower voltage, but to get the required power you will need to punch a bit more current through it. This wouldn't be a problem for most motors as the higher currents only flow in short spikes in cars.

The motor I am using is the Turnigy 3536/9. This has a 5mm shaft. For this application I actually turned the shaft down to 4mm and with the motor diff unit, don't use the original shaft at all. Why not give this motor a try? You're not exactly going to be much out of pocket if you don't like it!

[LongRat]

I've completed the motor-diff unit. Now with more than enough rotor support >:)

Here's the new stator arrangement. I'm using a 35x42x16 needle roller bearing to keep everything spinning in-line. It's the thinnest section bearing I could find, I'm just hoping it isn't going to be affected by carpet dust too much as it is totally unsealed. It isn't running any lubrication so it might not attract too much.

http://i43.tinypic.com/jfl26c.jpg

Here is the MDU completed. It comes in at about 1.5mm smaller at the largest point than the diameter of the most worn tyre I have used... should just about fit.

http://i42.tinypic.com/2ef021k.jpg

[morpheus2010]

Looking good LongRat. You could always try graphite powder as a dry lubricant. I use it wherever dust or grit may be a problem

£3.64 free postage - CPC - microfine-graphite-powder (http://cpc.farnell.com/kasp-security/k30050/microfine-graphite-powder/dp/SA02595) :thumbsup:

[mr. ed]

Graphite powder? I'd be afraid of causing short-circuit with that.

Thanks again for the info longrat

[dodgydiy]

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!

keda 450h is only a 400 class heli motor, very small and light, rated at 300w on 3 cells. i made up a carbon chassis mardave based car using that motor, a 35A ezrun and 1800 2 cell lipo's, 13 tooth 32dp pinion in those days!. intended to make it into an f1 style car but ended up just putting a lexan shell on it, was just under half the weight of a 4 cell brushed alloy chassis mardave. still have the chassis plate somewhere......

[morpheus2010]

Graphite powder? I'd be afraid of causing short-circuit with that.

Thanks again for the info longrat :confused:

Only applying powder to bearing should not be a problem there are no exposed/uninsulated electrics or electronic circuitry in the motor/stator.

[LongRat]

keda 450h is only a 400 class heli motor, very small and light, rated at 300w on 3 cells. i made up a carbon chassis mardave based car using that motor, a 35A ezrun and 1800 2 cell lipo's, 13 tooth 32dp pinion in those days!. intended to make it into an f1 style car but ended up just putting a lexan shell on it, was just under half the weight of a 4 cell brushed alloy chassis mardave. still have the chassis plate somewhere......

I thought you were talking about running the Keda direct drive, not with gearing. A 3200kv motor direct would be mad in a Mardave.

I'm not worried about graphite powder in the motor, it wouldn't cause an electrical issue.

[morpheus2010]

I'm not worried about graphite powder in the motor, it wouldn't cause an electrical issue. :thumbsup:

[cunawarit]

That's very cool! The idea of the car silently gliding by on the carpet is cool, not to mention seems supper efficient! I'm very impressed, brilliant work.

Anyway, I have a question regarding the motors, these are meant for planes and are sensorless. Correct? How is the throttle response? Nice and progressive or peaky?

[LongRat]

The throttle response is much smoother than a conventional 2-magnet pole system. It's like driving double cream. Not at all peaky. I run a lot of sensorless systems anyway, and the only problem I have with them is the sometimes slightly rough start up. This set up doesn't suffer from that, you would never know it was sensorless. I think because there are so many more poles and at any time the magnets are closer to a sensing pole, the induced EMF is stronger at a given rotating speed. This seems to give great feedback to the ESC and as a result, low uncertainty on rotor position. As I said before, you can enclose the motor in your fist and smoothly throttle up, and it will just start smoothly turning.

[morpheus2010]

Spotted this (ordered one) Also thought it may be of use for your motor development, cheap enough £7.85 :lol: Happy New Year :-)
Handheld Digital Laser Photo Tachometer (e-bay) (http://www.ebay.co.uk/itm/140938342840)

[mr. ed]

So... any more news from the race front?
I've ordered the 740KV one for a trial project, but had some troubles with the checkout from the hobbyking site.
I hope it turns up one of these days: paypal went through about 2 weeks ago...

[LongRat]

I've almost finished my new chassis and pod to accommodate the motor-diff unit, now it's a bigger diameter with the needle roller bearing. Other things have got in the way recently but I might get a chance to race this Friday.

[Dave Dodd]

What kv outrunner for say 13.5bl 2S

[LongRat]

Typical 13.5T RC car inrunners have kv parameters of 3000-3500 depending on the make etc. To spec a direct drive equivalent, multiply the kv of the 13.5T motor by the gear ratio you run and that will get you in the ballpark. For example if you run 25:75 that is a 1:3 ratio, so if your 13.5 motor was a 3000kv then your direct drive motor would need about 1000kv to be roughly RPM-equivalent. That's only part of the equation though, you need to ensure it produces enough torque and can dissipate enough power.

[LongRat]

I've finished my chassis and pod for the motor diff unit. All ready for testing on the track this Friday.

http://i62.tinypic.com/2ewoa6d.jpg

http://i60.tinypic.com/2nj901.jpg

http://i57.tinypic.com/2j0o36g.jpg

The chassis is 2mm carbon plate, the main difference is the cut out to accommodate the extra diameter of the needle roller housing. The pod is 14mm wider than a standard Mardave pod which makes the axle extensions shorter and less vulnerable (the wheelbase and track are standard V12 dimensions).

[cunawarit]

Impressive :) I said it before, but I love this idea. Cannot wait for you to report back on how it performs.

[SLEENAD]

Nice work on the front aswell!

[morpheus2010]

Cracking piece of kit :drool: Assume you have access to CNC facilities with the front end you have built :D

Looking forward to your on track report :woot:

[mr. ed]

Nice work indeed!
A small questions: why did you put the battery in front of the electronics: is it lighter?

And a small idea: the milled logo on the chassis bottom looks nice but a smooth bottom would be better for performance, nit? Maybe you could coulour some resin and have the logo stand out stronger whille keeping the bottom flat.

[LongRat]

Thanks for the comments guys.
To answer the questions - I have built up a nice workshop at home over the years, including a home made CNC vertical mill with which most of this car was made. There are only a couple of parts left which are original Mardave.
As for the flat floor, while in theory smooth would be better, it really won't make much of a difference I don't think. The reality is that the flow of air under this chassis will be heavily disrupted already at the centre chassis point by what's upstream - junction between alu bumper and carbon chassis, foam bumper lower edge and body shell. Plus there's that huge cavernous hole where the motor is at the back.

[SlowOne]

In LMP12, if you run a chassis that is flat from front to rear, the car will understeer at speed. The holes cut in 12th chassis' between the front steering blocks give the car high-speed steering. No, I don't know why either!

The other thing to bear in mind is that with a gap between chassis and ground of less than 3mm, the air becomes turbulent and the car gets spooky. Sine the car decks out at this level of ground clearance, that is a greater problem for handling so the poor air flow isn't noticed.

Many moons ago Phil Greeno made a full ground effect 12th car that actually worked quite week. Jason Deardon did it with a Pro10 car and that was awful! My approach is to do what everyone else does. Mechanically I can past muster, but aerodynamically I ran out of talent real quick!

[LongRat]

I built a ground effect car in 2001.

http://i57.tinypic.com/650px0.jpg
http://i58.tinypic.com/5y7psn.jpg
http://i59.tinypic.com/2i0g113.jpg

It was extremely stable at high speed. I couldn't compare it with and without the undertray though because it couldn't really be run without it.
They key is to get the centre of (minimum) pressure located in a position that is favourable to the handling you need. Too far rear and it will promote understeer, too far forward and the reverse will be true. If putting holes in the 1/12th chassis close to the front promotes high speed steering, and it IS an aerodynamic effect (big if), then this must be due to a shift in the centre of pressure under the car towards the front. But it could just be the introduction of more front flex and more mechanical grip under high loading.

[mr. ed]

LOL I didn't think of the aerodynamics when suggesting smooth is better.
I'm primarily a buggy guy and was worried of the contact between the chassis and carpet.

[LongRat]

LOL I didn't think of the aerodynamics when suggesting smooth is better.
I'm primarily a buggy guy and was worried of the contact between the chassis and carpet.

Haha! Hopefully it won't be an issue. I do quite like the idea of a coloured resin in-fill. Might mix up some epoxy with some paint and try that.

[mr. ed]

better use some kind of pigment: like childrens waterpaint disc, or crayon. The solvent of the paint might react with the resin.

I just ordered the moter again: finally got told by hobbyking my first order failed and they'll refund me :)

[LongRat]

Post up here when you have it in your car.
Just leaving for the track. Hopefully this will run well.

[LongRat]

Ran at Gloucester RC club last night. Failed to finish both heats due to the diff loosening. I was hoping the diff tension screw would be sufficiently secured with thread lock, but it wasn't the case. For the final I went with a load more thread lock and the diff setting was held, the car was superb and easily won. However as I had qualified last in the bottom final that doesn't say a lot, but the times were A-final competitive. I think with a bit of tweaking it will be a top contender. Overall I am very happy with it.
I will bond in a stud and use an M3 nyloc nut I think, that should fix the diff loosening problem.

[LongRat]

Ran last night with bonded stud, diff held together perfectly. Ended up 5th in the A final so pretty good result. Interestingly this is using a lot more battery energy than the solid axle no-diff version. I think it is a combination of being able to put down more power (so driving with more throttle more of the time) and friction from the needle roller bearing. Need to try some dry lube on it.

[morpheus2010]

Good to hear it's competitive. A sprinkling of magic dust could help ;) ( Graphite powder ) :D

[LongRat]

Yeah I have some somewhere, got to dig it out. Just can't remember where it is! :mad:

[morpheus2010]

Yeah I have some somewhere, got to dig it out. Just can't remember where it is! :mad:

Below supplier 50gram £3.56 free P&P if yer stuck for some :thumbsup:

CPCFarnell kasp-security/k30050/microfine-graphite-powder (http://cpc.farnell.com/kasp-security/k30050/microfine-graphite-powder/dp/SA02595?in_merch=Products%20From%20This%20Range)

[mr. ed]

Well, I had my first try with the 740Kv moter, and probably should have gone for the 1100Kv instead :blush:

I used the original yokomo YR-4 tourer and removed the entire front transmission and the center shaft with its spur and pulley. tapped the shaft of the moter through to the other side and mounted a 5mm bore pulley on the shaft. A shorter belt over the pulley to the diff was all it needed to finish the conversion. But I took some extra time and rearranged the electronics and switched to saddle packs. Al that to bring the weight more centered and further to he back: all possible now the fwd belt and spur were out of the way.


Unfortunately I only ever found one of those pulleys I now use as 'pinion' and it is clear it needs more teeth. The acceleration to top speed is immediate but it goes noticeably slower at top speed than a 540 mabuchi powered TT-01. It also comes to a stop way too quick instead of rolling out.
(No, the belt tension is fine, thrust me on that)

I guess I could try finding another pulley before upping the moter: anybody with ideas? It should be M3 module and a 5mm bore.

I do still have other ideas for use of the 740 KV moter, so It's not hat bad if I can't get the YR4 to work as it should. (The car was running great before, and 4WD, so I don't mind getting it back to its 'normal' state)

[morpheus2010]

Any chance of Pic's Mr Ed? :D

[mr. ed]

I 've just posted some pics in a new thread in the 'I made this' section:
http://www.oople.com/forums/showthread.php?p=840618#post840618

[fathead]

Longrat,
A possible alternative to that quite large (and I assume relatively heavy) roller bearing on the motor would be to use 3 or 4 small ball bearings spread evenly around the motor with small holders, could be a bit lighter and less rotating mass maybe.

[LongRat]

Yes, I considered the 'pinch roller' method but decided to do it this way as it would look more elegant. That's really the only reason!

[fathead]

That's cool.

I've been meaning to convert my Kyosho Spada to electric and had never thought of using an outrunner, was just looking at 360 size brushless, might have to give the outrunner a go!

[LongRat]

Nice wide car like that would be made for it. Interesting, I never realised they were 1/12 or that anyone made a 1/12 nitro on-road car. Never seen one before. Bet it is tough finding places to run it!

[fathead]

I haven't run it in years, we just used to run them on our 10th scale outdoor track in their own class

[LongRat]

https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-xpa1/v/t1.0-9/10475846_10155191697830167_5793790015168840079_n.j pg?oh=6c3864541e8e234e9c986fe423f036fe&oe=554BA629&__gda__=1435632191_3022766b5f3661a5f8bf14bcaae1a8e f

Long time since the last update!
I have gone through 7 iterations of the MDU, each having weaknesses and vulnerabilities that showed up in crashes etc. This final version has taken everything I have thrown at it and it runs strong at the sharp end of the field at our club. Very happy with the performance now and I won't be developing this car any further, although I'll definitely use this high efficiency concept in future project cars.

[mr. ed]

drool! still one of my favorites on this forum

[fathead]

Thread revive, just bought myself a Turnigy outrunner to do a pancar project

[mr. ed]

yeay!
Can't wait to see your next outrunner project.
I have scaler/crawlers outfiitted with outrunners now: a 780KV and 1100KV, and they are really performant low-cost resolutions that make your car that little bit special.