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Graham Windle
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4,445 Posts
Discussion Starter · #1 ·
Following JohnnyS challenge to get one of these things to run well I have decided to give it a go.
Straight out of the box the car is an absolute dog even with the magnet ,although it was possible to get the thing to lap with out deslotting it would slew side ways under braking and couldnt be pushed hard at all.
Basic problems with this car is that the chassis is far too flexible it is made from a polythene material and doesnt hold the axle or motor securely enough ,the rear tyres are too hard and the front tyres too soft ,the wheels also are way out of round . Removal of the magnet which is in the wrong place any way made absolutly no difference to the performance.
A quick test with other tyres proved that there was a chance I could get the cobra to run reasonably well
I will try to use as many of the original parts as I can to get the cobra to run well and set a target time of 8 secs around Slot -tech with no magnet which will mean I need to find a full 2 secs from somewhere.
The first step is to sort out the wheels and lower the chassis which I will show shortly
step 2 will be to sort out the motor mounting

step 3 will be to sort the body mounting which makes the car sit far too high

step 4 will be to tune the car to the track

Wish me luck guys
 

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Jim Moyes
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5,078 Posts
Which one you starting with, Grah?

On our tracks the Reprotec is the best of all the RTR Cobras, but even amongst the Reprotecs there are wide variations. The best one seems to be the yellow NC1 powered one. I think the blue road car is close behind, followed by the Hardtop cars. The orange NC2 powered one is just too powerful and the black road car has all the problems associated with front motored slot cars in general. Well I should say I assume it has, coz as it hasn't got a bloody driver in it I've never run it. Mutter, mutter, driverless slot cars, mutter, look bloody stupid, mutter mutter.

Anyway, best thing to do is get the yellow one and stick an RX4 in it (clicks straight in). I know coz one of our club members did and I've had to ban it for being uncatchable!

Mr.M
 

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Graham Windle
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4,445 Posts
Discussion Starter · #4 ·
I allready had the orange one mr m so thats the beast .
got it flying at the moment no probs plenty of poke and great power drifts ,at the moments its consistant at around 8.2 on my 70ft carrera nearly 2 full secs faster than when I started and now completly drivable , when Ive tested it at slot -tech I'll post some pics of whats been done.Ive kept almost all the original bits exept for 2 replacement tyres and the contrate which chewed its self up due to the flexibility of the chassis.
 

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Registered
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2,587 Posts
Yes Grah that`s the little devil I meant. I thought it would make a start to see if you could crack this but thought there may well be others out there who can think of a simiklar challenge? It`s the worse car I ever bought by some distance!
 

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Graham Windle
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4,445 Posts
Discussion Starter · #6 ·
go's quite well now john , my tracks very smooth so you can run very low but Ive set this one with 1/16" clearance so it should be ok on ninco and scx as well .I'll post some pics once my camera recharges I did some tonight but they came out carp .The motor seems very smooth and now that Ive cured the tramping and hopping its a pretty good little car.
So your all not waiting in suspense the basic set up that I have used is,
1. standard front tyres swapped onto the rears glued and trued.fronts replaced with ninco salloon glued trued and varnished
2. rear axlesupports made from popsicle stick Glued to side of motor to stiffen rear end
3.1/16" cut from top of radiator mould to allow chassis to sit lower at the front
plastic lump on rear mount cut flush with chassis to lower rear end.
Interior cut down to clear motor and reduce weight.
4.Replace magnet with piece of lead.
I also changed the contrate because the original one stripped ,ratio remains as original
 

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Graham Windle
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4,445 Posts
Thursdays tests at slot tech with the cobra wer quite good . The best lap I managed was 8.3 which is prety good for nc2 power the handling of the car is now both smooth and predictable giving easily repeatable lap times .The immitiing factor of the car is the gear ratio with the smaller diameter tyres reducing the top speed . On a shorter circuit I now think the cobra could easily hold its own alongside other classics ,any way heres a few pics




Pic showing interior cut away to lower c of g



side view showing reduced diameter of tyre



chassis stiffened by adding popsicle stick chassis members also shows weight behind guide
The addition of the stiffeners and the truing of the rear tyres made the most difference to the handling as the rear axle could no longer twist and cause the gears to loose their mesh

A change of gear ratio would certainly bring the cobra down under the 8 second target I set my self at slot tech but I think the article shows that the cobra despite its poor out of the box performance can be sorted and made into a reasonable car.
 

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303 Posts
Thanks Graham, I have one of these at home which i 'tried' to race.........it was a waste of time as like you say the chassis just flexes too much. Will now have to find some nice lollies so i can do your popcicle trick and see how that goes.

There is light at the end of the tunnel for this one, Mr M watch out
 
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