Mad Bull Radio Controlled Car Project

I was given a 2nd hand Tamiya Mad Bull, this car is based on Tamiya's DT-01 chassis and is a low end budget design from way back used in moels such as the hornet or grass hopper.

The Mad Bull's handing is terrible for many reasons and as friends were also getting back into RC cars I thought about using it to spend a small amount of money on to make it a bit more competitive.

Unfortunately, making the car faster increased its handling problems and so I've decided to see how far I can modify the car to give a half decent driving experience.

Upgrades

In order of when they were made on the car.

Battery

The Ni-Cads I was given were old and hardly kept a charge. New batteries were required just to get the out of the box speed from the car.

Voltz 3000mah 7.2v NiMH Stick Battery x 2

The difference in speed between the old Ni-Cad and the new batteries was noticable.

  • Cost £28.50

Ball race

Standard requirement if you want to get more speed out of a car, the cheap end of the Tamiya kits only come with plastic bushes.

Tamiya 58205 Mad Bull FULL Bearing Kit

  • Cost £7.00

Motor

Wanted something fairly fast but keeping in a retro theme, so opted for a Tamiya motor.

Tamiya 53930 Super Stock motor 23T Type BZ

  • Cost £44.99

Shocks

The standard shocks are just springs with no oil damping, so went for the official Tamiya Hop-up options, as I doubt I'd see the benefit of going for anything more fancy.

  • Tamiya 300050519 C.V.A. II Mini (front)
  • Tamiya 300050520 C.V.A. II Short (rear)

  • Cost £33.37

Tyre foam

I ripped one of the original rear tyres on the first run with the above mods. I figured this was due to the big tyres deforming too much under load, so added tyre foam to lessen this.

Schumacher 1:10th Truck 2.2 Foam Tyre Insert (Soft)

No ripped tyres on the next run, but the tyres came off the wheels instead on one side. So rather than go down the glue route, some more competitive wheels and tyres where needed.

  • Cost £7.49

Wheels

The DT-01 chassis can run most wheels but wanted to keep to a larger stadium truck size. Tamiya's Stadium Thunder.

These take a rear buggy size tyre on the front and a rear stadium tyre on the back giving me lots more tyre options than the original custom lunch box size.

Tamiya 58181/58524 Stadium Thunder, 9335228/19335228 Wheel Bag

  • Cost £13.49

Tyres

The original lunchbox style tyres are a hard compound so I wanted some tyres that would grip better on tarmac but not wear too quickly and still be versatile for other surfaces. I hope that these would improve cornering as the car hardly turns with the power down.

Electronic speed controller

From the last run I had little grip with the original tyres (with foam) on some gravel so the car fish tailed about all over the place, what made this worse was that with the original mechanical speed controller I only really had two speeds; very slow and very fast. This combined with no brake meant slowing down for the correct speed to take corners very tricky.

Would of liked to go with a Tamiya ESC but I could not find one that supported the 23T motor, So opted for something cheap and waterproof.

Hobbywing QUICRUN 1060 Brushed Waterproof ESC

With the removal of the MSC, servo and switch this upgrade should save some weight too.

  • Cost £22.39

Steering mod

The original steering has so much play that you can't drive the car with any precision. Most of this play comes from the metal rod from the servo saver as it is a fraction smaller than the holes in sits in at both ends and this slight movement is amplified at the wheels.

The fix here is to replace the metal road with a short tie rod that screws with a nut and bolt at each end to attach it without movement. In order for it to fit suspension mount will have to be cut a fair bit as shown and also the chassis slight to give clearance for the bolts.

As cutting the suspension mount increased its flexibility a strut brace was added between the shock towers to bring this back, which helped quite a lot but had to be removed when fitting the body. To get the correct length tie rod I cut the head of a screw and then cut it to the correct length.

Adjustable 36mm-41mm Turnbuckle Tie Rod Arms with Ball Ends

  • Cost £5.99

Tyres #2

The Pro-Line tyres grip really well, too well for the rubbish suspension on the mad bull. So I've gone to some hard original spec tyres for the stadium thunder wheels on the front that don't grip as well to lessen the barrel rolls when cornering. Hopefully this will be temporary whilst I get the suspension sorted.

Tamiya 50449 Stadium Blitzer Front Tires/Tyres (Blitzer Beetle/Stadium Thunder)

  • Cost £14.95

Gearing

With the new grippier tyres and instant speed that the ESC gives, the car now will pull wheelies and sometimes flips onto its back if it is given full gas when stationary. This meant I had to accelerate slowly at first to reduce this risk which as not fun.

Weight could of been added at the front of the vehicle to reduce this, but I did not want a heavier car! The solution was to reduce torque to limit the wheelies but increasing the pinion gear. This will put extra load on the motor but the car does not run for long on it's NiMH batteries so I figured it will be fine. A positive side effect is that the car will have a slightly higher top speed!

I increased the pinion by one tooth to 18, but the DT-01 gearbox does not allow different pinions to be used so an adustable motor mount kit had to be purchased as well.

Total spent so far

Not including the car, radio gear and charger which was given to me free.

  • £228.40 eek!

Photos

After motor, shocks, wheels, tyres and ESC

After shocks, wheels, tyres and ESC

Suspension mount cut

Suspension mount cut

Steering mod

Steering mod

Adjustable motor mount

Adjustable motor mount