Reincarnation of a Mugen bulldog

[tiger1]

Mugen bulldog probably was one of the most sloppily made cars from Mugen. I got my Bulldog in 1985 with the hope that the AWDS would do magic, dead wrong!! However, I did see a heavily modified Bulldog in a shop in Hong Kong as an on-road buggy (more info here http://www.rc10talk.com/viewtopic.php?f=30&t=9243) and that car won a couple of races using trinity motors and batteries. Some potential in the car.

I got this car a few years back and set off to do some work:
(1) with a lot of good luck, I purchased a set of brand new MIP aftermarket front and rear ball differentials with close to nothing (more info here http://www.rc10talk.com/viewtopic.php?f=33&t=7964)(this took care of the stiff original differentials, either too loose or too tight because they forgot to design a spring in it!!),
(2) add a few thrush washers in the middle differential to make it more reliable,
(3) custom made a graphite chassis + front and rear anti-roll bar brace,
(4) HPI off-road shocks, the original air-shocks was not really adjustable the only advantage was that they never leak oil, this oil leakage problem was only solved when Kyosho and Tamiya separately figured out that CVA shocks with a rubber diaphragm in 1985(!!!),
(5) added metal nuts inside the steering hubs at 4 corners (original ball ends on the hub would put out the of the hubs under hard impact),
(6) 4 aluminium CNC touring car rims (retro to the mid-80s Hong Kong on-road buggy theme see more about that here http://www.rc10talk.com/viewtopic.php?f=30&t=9243),
(7) direct steering in the front using a mini servo, uneven tie-rods with AE ball ends and a direct servo saver with graphite extension, greased and shrink wrapped the roll bars, (more detail here http://www.rc10talk.com/viewtopic.php?f=33&t=9626)
(8) get a repro Kyosho Beetle (Scorpion's cousin) body because the odd shaped monocore gearbox/chassis and shocks set up made it almost impossible to fix ANY buggy body without looking too odd,
(9) locked out the rear steering with F103 turnbuckles,
(10) change the hinge pins to hard type steel pins and added locking collars.

Will add some interesing electronics and will post more photos when the shell is painted. BTW, for the first time, my wife saw a shell on a chassis and she said it is pretty!!

[Mr. ED]

It looks wonderfull except for the steering system.
The short arm is aonly half of the long one

Maybe you can put a dual arm system like on a dogfighter, or a single link L shaped arm on top of the plastic frame with the servo behind it?

Also check the old car run section of timetunnel: there's a nice bulldog inthere which may have a better solution

[tiger1]

Thanks for the comments.

I checked the time tunnel site, all those modifications did not address the fact that the bulldog steering knuckles were incorrectly designed and all those nicer looking modifications did not improve the steering significantly using L-shaped bellcranks (still under steer).

[RETRO R/C]

There are several ways to attack the steering issue.

The best way we found BITD was to fit Kyosho Optima uprights and make a steering system from Square tubing - like a rack system:





I like your mods - but be wary of the solid chassis plate - as the roll cage will snap easily with such a solid mounting point. I hope that servo lasts - as if you are getting good grip - it may not have enough torque to hold the car on line........or worse - strip the gears (even with the Kimbrough)

Good on you for restoring a much underestimated car.

Cheers

Darryn

[tiger1]

Thanks for your kind words.

When you use Kyosho steering hub, can you keep the original shafts?

[highwayracer]

I just measured the bulldog axle the other night and it's 5mm. So you can still use it with the optima knuckle (5 x 10 mm bearings) provided that the axle is long enough.

[Bormac]

Thanks for your kind words.

When you use Kyosho steering hub, can you keep the original shafts?

I have found the driveshafts for the Bulldog to be a little too long when I use my optima hubs and axles. Im currently in the process of shortening some Option House universal shafts for my car.

[tiger1]

If that is case then one may use TA04 or old TA05 front hubs. I was told that they are indentical to the Kyosho front hubs.

[Mr. ED]

Tamiya usually sticks with 5x11 bearings (and so did yokomo on the yz-10 series). Sometimes this will give compatibility issues on using the axles designed to go with kyosho 5x10 bearing hubs.
If the separation between the bearings is the same thickness the 5x11 setup will end up just a tad wider. Unfortunately that can be enough for the hex to press the bearings in case of crosspin designs, or in case of the traditional kyosho alu hex: not gripping on the conical surface.
Because of this I had to use lazer ZX5 parts on a hex conversion for the yz-10 works design.
The ZX5 steering knuckles are still very close in design to the optima parts. (Though now they switched to the losi style in the updated model)

Jason, what will be the length you need in the end?

[tiger1]

A bit more work in that last few days.

Got the body trimmed and body mount made. Started painting the shell now.

[tiger1]

I have also lowered the graphite front roll bar mount in order to mount the body lowest possible without changing the suspension geometry

[tiger1]

Body painted

[tiger1]

New shell completed. But I just do not have ANY Mugen sticker...

Can someone donate a Mugen sticker? May be even a small one from Mugen gas buggy...

[tiger1]

Push this one up also, for those who has the interest on the topic

[emerson_shih]

Good job Tiger~
But I think the wheel is a little bit small.