RC Tank Warfare community hobby forum

HERMAN BIX wrote:Be it a Mini Cooper, or an E-type jag, British racing green by any other name seems to suit Tanks too !!
Love it & great to see you back into a project Mr 43rd

Many thanks, HB! As it happens, I had three early Mini Cooper 'S's: one short-stroke 970cc model (very few made)- a real high revving screamer, and two of the Mk 2 1275cc model. They went like sh*t off a hot shovel. These were, of course, the original 1960s Coopers, used in the 'Italian Job' (" You're only supposed to blow the bloody doors off!..."), and which also won the Monte Carlo Rally- not the BMW versions we see these days.
The hallway used to be full of bits; even a couple of engines. The ex-wife flipped when she found an engine block in the sink That's perhaps part of the reason why she became an 'ex'.
Here's the progress to date on the Comet and Cromwell:



I've posted the same pics on the Cromwell thread. That's just in case enquirers find the one, but not the other, in a future search.
Edit: I've corrected a few grammatical oddities (missing words mostly )

That's a fine looking pair of tanks you have there Roy, a real couple of beauty's

Cheers, Lee.

Agreed! Nice sharp photos really showcase your work. Very nice.

Thanks, Lee and Jim. A little support goes a very long way

Top work, they look like they came straight off the production line.

wibblywobbly wrote:Top work, they look like they came straight off the production line.

Thanks, Rob!. I like the new hot (nuclear?) avatar, by the way

two outstanding tanks! I've enjoyed your story about the engine block in the sink as well

We’ve all been there with car or bike parts in places they shouldn’t go !!

I can only imagine the look on her face, if she'd come home to find an army surplus Comet A34 in the drive,... instead of yet another battered, veteran Cooper 'S', with its engine swinging beside it in an engine hoist ,... above an expanding pool of oil.
That gives me an idea...I now have a very large (1/4 acre) garden, and a tolerant part-time partner.
Anyway, for those interested in the Comet/Cromwell suspension. If you check this cutaway diag out, you'll see that the suspension strut uses two compression springs (not a tension spring as in the scale model): a fine inner one, and a beefy outer one. When the wheel hits a bump ( or 'bermp' if you're Inspector Clouseau), the body of the damper is pulled downwards by the axle arm, compressing the spring against the collet which, in turn, is held in a fixed position by the Centre Bar- resisting the downward movement. A hydraulic shock absorber, above the suspension strut,, then dampens the action.

I was thinking of starting a thread on Suspension systems, and how scratch build tank/truck/AFV modellers, as well as scale model manufacturers, determine how soft, or hard, to make a suspension system. No matter how detailed your scale model is, if it bounces around like a jumping jack firework, when encountering obstacles, it's not going to look impressive. In fact, it will look like a toy- and that's not what we want.
Ideally, you want your suspension to emulate the real thing, when mounting obstacles, or crossing bumpy ground. Driving over a rock should produce this look:

(This was the Comet in US paint, prior to the SCC15 paint job.).
Adverts for Heng Long tanks, on Youtube, now stress the realism of suspension systems- of their proportionate scaled-down reaction to meeting obstacles. Running over Dennis the Menace, would be one example:

It has to look convincing.
For small obstructions, the tank should stay almost level, ideally. For this to happen effectively, the strength of the springs has to be proportionate of the weight of the tank. That way, you get the right amount of deflection, wheel after wheel, when grinding Dennis into the ground. For this, the springs- whether tension or compression- have to be soft enough to move individually, but firm enough to bear the weight of the tank.
Believe it or not, there's actually a formula for calculating spring strength:

Mostly this is used for springs on sports cars, but could be scaled down for models. Here's a guy actually using it to determine the right spring to fit to a Lotus Elan:



and this is how to use the spring formula/equation:
https://suspensionsecrets.co.uk/how-to- ... ing-rates/

When you build a scale model, then I think that hardest task is-(the one that turns hair grey quicker)- finding the right spring resistance, and the right type of spring.
The Comet will run with the springs I fitted, but I found that- especially at the back with the weight of the motors-if I pressed the back of the tank down, it took to long to recover- or return to it's default position, that is.
Here it is creeping back to battery, so to speak (a slow recoil... ):


Worse still, without bump stops fitted, the wheels can actually make contact with the return rollers. Now, that can't be good. So, I shall think about devising some bumpstops before trusting a MFU with this drivetrain. The TK 6.1s (the MFU I'm thinking of using) was fairly expensive, and a bad lockup could burn it's precious essentials...