The rise of Frankenbear

[Ray_ve]

As promised, I'm starting a build overview of Frankenbear, a heavily modified Big Bear I'm working on.

This project started with the car that got me back into RC cars, a few years ago.
My first love (and those are the hardest to forget), a Marui Big bear.

https://re74.imgur.com/all

I bought this car cheap, and although rough looking it was a runner so I had a few runs with it.
When the nostalgic feelings were satisfied, I decided on a stripdown to see is what real state of the car was.

As we all know, after 30ish years, thing start going south.

The tires were in 1 piece, but dry.
The gears in the gearbox about half-way worn.
The chassis had splits in the battery box, both sides.
The body itsel, despite its bad paintjob, was in 1 piece! Score!

 

So it was time to have some fun modifying this old beast. To do list:

- New tires.... somehow.
- New gearbox and/or gears.
- Fix cracks and patch it up.
-Ball Bearings!
 

For now, this post mainly shows the differences between a regular Big bear, and Frankenbear.

More posts on the build details will follow when I recover the data from my laptop.

 

Left: Original Big Bear, Right Frankenbear with a Team Bluegroove body from my other bear: Basherbear!

 

And as a glimpse from my latest creation, original bear vs. Bullheadclodbear (working in the body, its in filler primer now)!

[geniusanthony]

I like frankenbullheadclodbear, it's fun to say too!

[Ray_ve]

First thing after stripping the bear down, had to think of a way to get a new gearbox.

I believe it was somewhere on this forum, google pointed me to a thread that said 'Why not put a grasshopper gearbox on it?'.

Thankfully, I still had a lunchbox gearbox, so I thought I would give it a try!

Moddeled and printed new suspension arms that would fit the lunchbox gearbox, and join with the chassis.

 

Then, a trail fit. Heee, not even half-bad!

 

Next, suspension. I also dug up some oil-dampers that belonged to my long discarded Kyosho Nitro Corvette.
Since they could not go into the original positions, I made a strengthener plate to hold them at the end of the chassis. It is fixed to the chassis using double-sided tape and 2 screws were the original springs sit.

 

And offcourse, no car is complete without tires! Found these great shevrons on aliexpress. 130mm diameter and 70mm wide. Original bears are 110mm by 80mm.

And adapters for the gearbox, as these are regular 12mm hex.

 

And when it is all together:

 

A sturdy gearbox, ball bearing equipped offcourse, and new tires. Job done on the backside.

And because of the way this is mounted, no hole drilling in the chassis. This mod is reversable.

Only one tiny issue...... the back end sits a lot higher from the ground with this gearbox and bigger wheels, so the front suspension is now too low.

Next post: Front suspension.

[yogi-bear]

I'm liking this thread! I have two Big Bears that need restoring one day, one will be a full rebuild, the other a runner, so keen to see what you do with this, especially with the steering

[King Zulu]

That is one of my all time favorites, mine had the optional 48P gear set. Cool build...

[Ray_ve]

On with the front suspension.

To get the front suspension on the same height as the rear, One could simply make longer uprights that the big bear frotn suspension uses, bit this would put the steering servo into a very high position compared to the original mounting of the steering point.

Another problem I had was that the new front wheels are also 12mm hex, while the front axles on the big bear are of the same type as the lunchox: stationary, not rotating.

 

So I decided on a whishbone suspension, and had our aliexpress friends send a set which are ment to be on a Kyosho Javelin I believe (since I was already using Kyosho shocks anyway).
I still had a set of 4WD axles and 12mm Hexes from my Corvette, so these could also be used to rotate and mount the wheels.

 

Started the front suspension by moddeling and printing  a plate that sits below the front chassis and bolts into the servo mounting holes, and a U bracket that holds the plate at the front and bolts into the original suspension swivel holes using the original M3 rod.

 

The steering servo mounts to this plate, and another shaped piece extends further down to hold the lower whishbones. The upper adjustable bones screw into the U bracket.

Here is the steering servo, missing its servo saver but you get the idea. Steering rods are now 3mm rod, coupled with ball links.

 

This is the view from the front, with the shocks in place.

 

Finally, the chassis was now on 4 wheels, with the bottom of the chassis sitting about 2x higher compared to original.

Next post, the battery box repair and the test drive!

[Ray_ve]

Last steps, battery box repair and the test drive!

The battery box had splits and breaks on both sides. I decided to repair this by extending the box, so it would also accept the 8.4V stickpack that came with the car.

So new extended side covers were moddeled, printed, and glued in place with epoxy glue.

 

And then, the long awaited test drive!.

Because of the large diameter tires, and the gearbox uses a 21 tooth pinion with the motor directly bolted to the box, it is fast!

Well, at least compared to the original. With a silver can it is about 2x as fast, with the 35T motor I use now, about 1.5x as fast.

It also steers well.... at low speed!

 

The test drive revealed a design flaw that is very logical.... once you see it in action.

Because the chassis is much higher compared to original, and the speed has increased, any attempt to turn while at more then half speed will result in the car flipping on its side!

If a NiMh 8.4 pack is used, it will also do a full 1.5 tunr flip because of the battery weight high from the ground, with a much lighter weight 2S 2200mAh lipo it will only tip over.... Hence the reason I changed it to the 35T motor, its there to reduce speed as part of damage control.

 

So.... to wrap things up: this has been a very fun and interesting build for me. And despite its handling problems, it is still a fun truck!

I will not use the original body for this truck. I found a complete and in very good condition big bear chassis, which only needs a body and wheels. Since I have these left over from this truck, I'll use those to build a complete and original Big Bear.

Frankenbear will get a polycarbonate bear body, thise can take some abuse. And bumpers with lights are still on the drawing board. Who knows, maybe with some repositioning of the gearbox to get the chassis lower, its handling will improve.

But I plan make it a complete car, So some time in the future I'll post it with its new body.

 

And if anybody is interested, I'll do a topic on Basherbear, which is (as the name implies) the big bear lookalike I use for bashing and recreational driving.