TOPIC:

Good point, I was assuming more turns would mean more torque.
We'd have to see how they'd actually behave in practice though...
Which seems to be the point of the topic.

I don't see much of an argument btw. Maybe just an overstatement.
Let's not make it one in either case.

Hi I would like the hear some feedback from someone who has run a clodbuster or bullhead with sport tuned motors vs standard. A few points to recap as this thread seems to be getting off topic.

As some guys are drawing comparisons to 3 phase motors. A 3 phase motors wiring and circuit protection is designed to handle up to 6 times its full load current during start up when a current limiting device is not used. If the load is not great it will not see more than a few times its running current so 2 or 3 times ie while bench testing the current will flash up so briefly most clamp meters will not settle on a value.

This Rerelease Bullhead runs a electronic speed controller ie up to date technology. Comparisons the star delta would be more at home in the days of mechanical speed controllers. Star/ Delta 3 phase motors starters have been slowly phased out in industry since the early 90's I have not installed one since 97 but have repaired many with damaged contactors of replaced them with soft starters or vsd'd. A star/delta motor requires both ends of the windings to be brought back to the control gear(6 wires in a 3 phase motor) where 3 contactors and a timer connect the motor first in star (2 windings in series) then delta 1 winding only. Therefore Star torque is less than delta as the resistance in the calculation is double. A motor while starting in star if loaded still sees heaps of current, granted less than it would in delta. It also sees a badword of a lot more current in star than a true current limiting device. With the price of copper now days unless the motor run is very short a true electronic current limiting starter would be cheaper to install and run.

This method is crude compared to the days of electronics (ie now) where soft starters and variable frequency drives actually ramp the motor up gently by reduced voltage and frequency during starting. As this car is dc when don't have the luxury of controlling frequency we use the fet's of the speed controller to do a similar thing.

My background for anyone interested is I am a full time Industrial Electrician employed in installation, line control and breakdowns for a large Australian food procesing plant. SPCArdmona owned by Coca Cola.

Don't make the mistake of thinking if a motor is making more power it is using more current.
THE HORSEPOWER OF A CAR IS NOT MEASURED BY HOW MUCH PETROL IT USES!

Efficiency plays a big part. The sport tune current graph sits vitually on top of the standard silver cans until near max rpm. So it is vastly more efficient and more powerful for the similar current use and run time the reason we are interesting in using it. I assume i will use more battery with the sport tunes yes but not heaps more. Brushless is out of the question for this car but as an example brushless motors are efficient enough to use less current and make more power.

What will happen??? Its all theory for now??? Its been 15 years since doing year 12 physics and about 12 years since trade school. My last shed project was a dyno proven 500hp 347 cubic inch v8, but at the moment all I want to play with is rc cars!

I believe the motors are doing different amounts of work to each so different heat and current draw. They are not a perfect match due to one having advanced timing but they are still similar enough that the forward running motors speed under load will not exceed the speed the other motor can produce.

The other motor is not a hand brake or working against the first, they are producing different amounts of power but in the same direction therefore some help. The motors are coupled magnetically (through their repective magnetic fields) if that makes any sense ie the magnetic field if what is pulling the motors therefore there are allowances for differences.
I think the worst consequence will be more brush arcing from the reverse running motor, this will probably be the part that rains on our parade. (Ie Ruins the day and also the life of the motor, not sure if this saying is used universally).

Someone also stated the silver can runs in different speeds each direction so the sport tunes probably aren't any worse.

I assume they would work in a similar way to real world applications such as several goods trains coupled together, twin or triple outboard rigged boats and the good old 2 horse and a cart.

A bullhead would be the simplest and with motors around now probably fastest with a single motor set up, but the clod and bullhead are all about being different 2 motors is different than the norm and cool. Using sport tuned is about staying true to the tamiya hop up theme, I could easily order 2 brand x neutral timed motors online.

Eddrick raised a good point earlier about overpowering rc cars and spending cash on repairs. If the sport tunes are too fast and just cause crashes then we will go back to silver cans or similar. But what is wrong with trying out a more efficient and more powerful motor, I have and electronic speed controller so can feed in the power and control the top speed as I desire. This car will not be bashed, I have a CEN gsr5 converted from nitro to brushless and a brushless db 01 to kill, cool retro Tamiya cars are to enjoy. I am about to aquire a bigwig that will restored to standard conditon.

Welcome, vara347. Brother of vara351 I assume...

Topic was moved to the technical section.

Welcome on board

I must say I'm somewhat relieved to see you have an intelligent & inquiring mind - I had thought your quest for power/speed might have meant you were the RC equivalent of a spotty oik fitting a baked bean can silencer to their 50cc stinkwheel to "make it faster"

I must admit to some bias (based on experience) regarding the futility of trying to make a Bullhead/Clod go faster, but more on that later.

re my point about the rear motor (and/or rear ESC / rear battery in dual everything setups) getting hotter - I'm sure that this is down to weight transfer on accelaration, meaning that the load on the rear motor goes up (and the load on the front goes down) - any car will squat at the back, but perhaps not as markedly and not as often as this truck - the nature of the beast means you tend to do a lot of stop/start driving (or short bursts of power, followed by slowing down & attempting to steer) - it's not something you tend to do laps with.

I'm not clear on how much of the Sport Tuned's extra power comes from having 23 turns & how much comes from the advanced timing, but I'm very sure that running in reverse, that 4 turn advantage will be cancelled out by the timing being effectively retarded, making the rear motor no better than a silvercan. This is a problem as the rear motor tends to do a lot more work - depending on the surface I think what will happen is that either the rear motor will act like a drag brake, slowing the truck down to dual silvercan speeds, or, on looser surfaces, I think the rear will be pushing while the front wheels are spinning, in a cartoon-like "binka binka binka!"


This is semi-theoretical as I haven't put two sport tuned motors in that chassis...

My experience with putting faster setups in dual motor trucks (19T's (with advanced timing, I think) in a clod, 19Ts (ditto) and 8.4v in a Twin Det) is that they make more noise, have far worse body roll/pitching, worse understeer, meaning less control & potenially more crash damage. This, to a boy racer, means it's much faster However, I don't believe they were actually accelerating any faster, and the top speed was still dissapointing.

Some might argue, however, that 19T motors are a point where you really need a smaller motor pinion to get any benefit over silvercans with the standard gearing, so my theorising is not translatable to Sport Tuned motors, where smaller pinions are still
optional.

Overall, I think twin sport tuned motors are a bit of a waste of time in a Bullhead, and I would expect run times to be shortened by 30% ... but it will be more spectacular to drive, and if you're that way inclined, that will be all the "proof" you need.

BTW I'm not against the Sport Tuned motor per se - in fact it's my motor of choice in just about any other Tamiya car/truck - approx. 30% more power/speed for 20 GBP or so, without the need to change the gearing? I'd be a fool to say that was a bad idea, when the only trade off is a 30% reduction in run time, which is offest by having much larger capacity batteries than we used to have back in the day ...

My feeling with the Clod/Bullhead chassis is that you should enjoy it for what it does - be hugely physically imposing, and deal with all surfaces (including snow & water) better than any other stock Tamiya - but speed is never going to be something it does well, or even at all.

vara351 wrote:

I am feeling a little disappointed at the direction this thread seems to be taking, I feel it is turning into an argument rather than an intelligent conversation...

With all due respect, you set the tone for that by intially asking for advice, then appearing to disagree with anyone that offered it, although I admit some of the paradigms used to explain the likely results haven't been that cogent ...

Or, the playground version - "Well, you started it "

Jonny wrote:

Or, the playground version - "Well, you started it "

Yeah, I started it by starting this Thread!! Electrical theory can be hard to comprehend for most people, and I am lucky to have a brother and best friend who is very fluent in this area. I believe intelligent arguement is healthy, even if we disagree it does help to strengthen your own viewpoint. Yet at no point do I believe I have asked for sarcastic comparisons or answers in rhetorical questions.

You raise another fair point - Even IF our predictions regarding the sport-tuned motors are 100% correct, will it make the Bullhead a better truck? Now there is a question that all the good advice in the world will not deter Bro and I from finding out ourselves!

vara347 wrote:

Hi I would like the hear some feedback from someone who has......

Hey Bro!! My eyes and head hurt after reading all that!!

Sorry, my "sarcastic comparisons" etc weren't meant to be taken in offence or anything like that - I tend look at problems to the Nth degree & try to visualise what might happen at both extremes of "What's going on" & make the system simpler/better/more reliable (It's one of my jobs to debug mal-engineered electrical/mechanical/chemical process systems, another of my jobs is to design & build them properly & yes that includes Coca Cola, as well as other well-known food/drink/pharmaceutical/water/power companies). My selection of words/comparisons is the only way I know how to clearly get my thoughts across & shouldn't be taken literally.
I can see your points & don't disagree, I'm just trying to add "What about if this happens, have you considered that?", you asked for help & I was trying to be helpful

I for one always appreciate your (educated) input, eddrick.
The open way of expression may need some getting used to.

I've been looking into the differences between a silver and black can...
First of all I'm still wondering about the exact origin of the Sport Tuned.
Mabuchi simply doesn't seem to make a generic 23 turns. Still I believe they are 23T and not 27...

www.mabuchi-mot..._0305.html

From a web search, it looks like the advanced timing is 27 degrees.
The amount of torque listed earlier on a silvercan (6527) does not match with what Mabuchi says :


At 7.2V it would be 237 g-cm...
They also have advanced timing - 3 degrees from what I conclude here.
Efficiency should only start playing a role at higher revs so that leads me to think it will give a black can a run for it's money when it comes to acceleration. Initial torque is only about 13-15% less, which is around the productional deviation either motor can have. I've extrapolated the torque curve for that :


Most interesting thing - you could actually run a silvercan on 9.6V and a Sport Tuned at 8.4V max.
And the fact that the current drain is almost exactly the same...

Even in slowmo, this Clod seems to be coping well with a couple of Sport Tuneds :