MadInventor

3S LiPo Mad Bull mod

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As the speed run thread has started a new category for silver can cars, I thought I'd have a go at it with my Mad Bull. I've been wanting to mod the chassis for a while now to improve on the stock steering installation, and also want to be able to use LiPo battery packs.

So the first thing to do was to remove the excess protrusions from the inside of the chassis and make a slot in the back of the bathtub:

img33435_8202017103407_1.jpg

to allow fitment of the LiPo into the chassis:

img33435_8202017103407_2.jpg

After that I made a new plate to install the steering servo. The plate allows the servo to be mounted lower so I can bin the stock steering connecting rod, which I replaced with a old 3 step speedo connecting rod.

img33435_8202017103407_3.jpg

img33435_8202017103407_4.jpg

I also machined a slot into the back of the plate to retain the radio tray, which is going to sit behind it:

img33435_8202017103407_5.jpg

This next pic shows the steering servo fitted, and the foam I fitted either side of the LiPo to hold it rigid in the chassis:

img33435_8202017103407_6.jpg

This is new radio tray, which when secured also holds the battery in the chassis:


img33435_8202017103456_1.jpg

It's held in at the front with slots machined into both plates:


img33435_8202017103456_2.jpg

Made some brass 'body mounts' to screw into the chassis to hold the radio tray down:


img33435_8202017103456_3.jpg

Radio tray fitted with body mounts. I can remove it by just pulling the 2 body pins.


img33435_8202017103456_4.jpg

The next pic shows the radio tray populated, there's even room for the GPS speed meter:

img33435_8202017103456_5.jpg

I can even read the GPS through the drivers window :)

img33435_8202017103456_6.jpg

Not bad for a (long) days work, tried it out on the drive in the dark but it's been raining so nothing but wheelspin and white sparks coming out of the motor at full throttle. Need to wait for an opportunity now to run it and get a good speed measurement.

 

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1 hour ago, Nobbi1977 said:

Looking good. It should make interesting handling at speed.

Yeah, I'm a little concerned that the weight of the battery is too far forward, but I couldn't butcher the existing battery hole through the chassis without destroying the strength in it. Only time will tell when the ground dries up.

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I like that, the battery is far better protected there. Maybe not from water mind as the tub normally catches it all but the metal plate will help in that respect.

Will be interesting to see how you get on with that.

I'm struggling to gain much more performance over 2s from my silver cans running 3s. Most of my car's are big wheelers ie the Monster Hornet and running the Quicrun 1060 ESC. I have two different 3s batteries and I really don't know if it is the battery capacity holding them back and the larger wheels are causing more of an amp drain than the battery can supply. On paper the batteries should be man enough. 99amp discharge? Could the motor be pulling more amps than that, or maybe the battery is over generously rated?!

IMG-1208.JPG

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22 minutes ago, Nitomor said:

I like that, the battery is far better protected there. Maybe not from water mind as the tub normally catches it all but the metal plate will help in that respect.

Will be interesting to see how you get on with that.

I'm struggling to gain much more performance over 2s from my silver cans running 3s. Most of my car's are big wheelers ie the Monster Hornet and running the Quicrun 1060 ESC. I have two different 3s batteries and I really don't know if it is the battery capacity holding them back and the larger wheels are causing more of an amp drain than the battery can supply. On paper the batteries should be man enough. 99amp discharge? Could the motor be pulling more amps than that, or maybe the battery is over generously rated?!

IMG-1208.JPG

My cells are rated for 85 amp max, I think the hobbywing 1060 is rated at 60A max, so unless the speedo is cutting out they should be ok. I've tried 3S on these batteries in my FAV and Wild One and had good results with them compared to 2S, but the motors were new in both of them. When I get to do my speed runs I'll try and remember to run 2S and 3S for a straight comparison. (The mods I made to Bull still allow me to use a stock 2S battery in the standard battery compartment.)

Edit, just checked the spec on the 1060, it's 60Amp constant, 360Amp burst.

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My Silver cans were also new. I even just tried with a brand new Torque tuned at the weekend. It gives barely any more power than 2S.  I saw your Wild one runs and that runs well on 3s. Thanks for the ESC rating, perhaps a silver can is pulling more than 60A with big wheels?!? The motor does get very hot! I'd like to buy a current tester and see.

With the batteries, because it is 3 cells, does that mean that each cell can only deliver a max of 33amps on my battery above or am I correct in saying 90amps should be the theoretical max discharge (2.2x45c).

Found this from their website which should answer my above query... 

Discharge rate (continuous): 45C (99 A)

Should be well within spec unless it's the ESC limiting it, but then your wild one was running a 1060 wasn't it? Perhaps with the smaller wheels it was within the ratings.

I'd be surprised if the 540 was drawing more than 60 amps but then judging by the heat it could well be. I'll try again on a brushless setup and see if I get a noticeable improvement. On my previous 3s battery I did about 3mph more on a BL set up but they were on these punier batteries...then again BL is much more efficient and with better wiring. My dual brushless 4x4x4 WT is only drawing 21amp average continous by comparison going on battery duration though I don't know what peak/burst would be.

IMG-1090.JPG

These were only 1.8 x 25c = 45a discharge rate.

Cheers

Nito

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12 hours ago, MadInventor said:

As the speed run thread has started a new category for silver can cars, I thought I'd have a go at it with my Mad Bull. I've been wanting to mod the chassis for a while now to improve on the stock steering installation, and also want to be able to use LiPo battery packs.

So the first thing to do was to remove the excess protrusions from the inside of the chassis and make a slot in the back of the bathtub:

img33435_8202017103407_1.jpg

to allow fitment of the LiPo into the chassis:

img33435_8202017103407_2.jpg

After that I made a new plate to install the steering servo. The plate allows the servo to be mounted lower so I can bin the stock steering connecting rod, which I replaced with a old 3 step speedo connecting rod.

img33435_8202017103407_3.jpg

img33435_8202017103407_4.jpg

I also machined a slot into the back of the plate to retain the radio tray, which is going to sit behind it:

img33435_8202017103407_5.jpg

This next pic shows the steering servo fitted, and the foam I fitted either side of the LiPo to hold it rigid in the chassis:

img33435_8202017103407_6.jpg

This is new radio tray, which when secured also holds the battery in the chassis:


img33435_8202017103456_1.jpg

It's held in at the front with slots machined into both plates:


img33435_8202017103456_2.jpg

Made some brass 'body mounts' to screw into the chassis to hold the radio tray down:


img33435_8202017103456_3.jpg

Radio tray fitted with body mounts. I can remove it by just pulling the 2 body pins.


img33435_8202017103456_4.jpg

The next pic shows the radio tray populated, there's even room for the GPS speed meter:

img33435_8202017103456_5.jpg

I can even read the GPS through the drivers window :)

img33435_8202017103456_6.jpg

Not bad for a (long) days work, tried it out on the drive in the dark but it's been raining so nothing but wheelspin and white sparks coming out of the motor at full throttle. Need to wait for an opportunity now to run it and get a good speed measurement.

 

Very nice Build!

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35 minutes ago, Nitomor said:

My Silver cans were also new. I even just tried with a brand new Torque tuned at the weekend. It gives barely any more power than 2S.  I saw your Wild one runs and that runs well on 3s. Thanks for the ESC rating, perhaps a silver can is pulling more than 60A with big wheels?!? The motor does get very hot! I'd like to buy a current tester and see.

With the batteries, because it is 3 cells, does that mean that each cell can only deliver a max of 33amps on my battery above or am I correct in saying 90amps should be the theoretical max discharge (2.2x45c).

Found this from their website which should answer my above query... 

Discharge rate (continuous): 45C (99 A)

Should be well within spec unless it's the ESC limiting it, but then your wild one was running a 1060 wasn't it? Perhaps with the smaller wheels it was within the ratings.

I'd be surprised if the 540 was drawing more than 60 amps but then judging by the heat it could well be. I'll try again on a brushless setup and see if I get a noticeable improvement. On my previous 3s battery I did about 3mph more on a BL set up but they were on these punier batteries...then again BL is much more efficient and with better wiring. My dual brushless 4x4x4 WT is only drawing 21amp average continous by comparison going on battery duration though I don't know what peak/burst would be.

IMG-1090.JPG

These were only 1.8 x 25c = 45a discharge rate.

Cheers

Nito

My FAV run was also with a 1800mah battery, I think the monster hornet is possibly geared too high and the motor can't rev, so adding more volts is not helping much. If I remember correctly, I was getting about a 40% increase in speed going from 2S to 3S, but both the wild one and FAV are light cars. The motor in the FAV(with TLT-1 wheels and tires)  did get noticeably hotter on 3S than the wild one , which has smaller diameter driving wheels, so perhaps the large tires are killing the performance.

With regard to the cells, each cell can deliver 90A, they are connected in series so having more cells does not increase the current delivering capability.

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Just been and done a quick test run with Mad Bull, and got 48kph / 29.8mph out of it. Not bad and about where I expected it to be.  The car tracked well and maintained a straight line, and as long as I didn't give it hard throttle from a standing start it pulled away nicely without spinning out. Back end bounced a bit over the bumps, but then it was doing nearly 30mph. Motor started to get to the upper end of 'warm' after a about 5 minutes, so decided that was ok for a first run. Got to decide what, if anything, to do next to make it go faster. Could put a slightly larger pinion in it, but that will just cook the motor faster.

I'm also thinking that the diff will need locking if I'm going to use anything more powerful than a silver can in it.

 

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