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TOPIC: Mardave Cobra - another quicky resto

Mardave Cobra - another quicky resto 7 years 3 months ago #12330

This is my box.... exciting, isn't it!
Would you like to see what's inside?
Tough, get your own box!


My brother's birthday was approaching rapidly & I was running out of time to get him a present, & really had no clue what to get him. Then, I remembered (After reading Jonny's cars for sale topic) that he's got a Cobra fetish...
Maybe I could land one for sensible money? So, I started looking.
Typically, the second I started looking to buy, the second hand prices of the Cobras (& Meteors) went inexplicably through the roof. Don't worry if you're looking to buy one, now I've bought one the prices should plummet to less than normal!
So, basket-cases & parts listings were the order of the day, again.
Found a nice man on Ebay listing some Cobra bits, but all separately, so to avoid being dumped in the normal situation of buying half a car & then having all other related parts disappear off the face of the earth, I messaged him to ask if he had any more of it kicking about (I won't start a project until I can see if/how I can finish it).
Turns out he's got a couple of cars-worth of bits, so I asked him to put me together a "Box" of enough bits to build one. (Cheers Paul, if you happen to read this!)

Contents of the box, so what have we got here then? Looks pretty much complete to me


As usual, 1st job is to reduce it to component level

then clean & inspect everything, to get a better idea of what needs to be done & to make a shopping/to-do list


Chassis badly scratched, body badly painted, both will get stripped & repainted



Not sure if the motor's original or not, but I took a pic of it to make Jonny giggle (Note the writing on the side) - Looks like an HPI, Annsmann, HSP, travel hairdryer, tyre inflator etc motor to me, maybe I can add Mardave Cobra motor to the list? Certainly wasn't born in Norwich with the rest of it!



Ok, I'll sort the chassis first, that can be drying while I occupy myself with other stuff, & hopefully it'll be ready for when I need it.
Nitromors had the paint off reasonably quickly, then I thrashed it with the power sander to get the worst of the scratches out. Aluminium is a pain to get paint to stick to, so I thought it best to leave the angry sanding marks as a better "key" for the paint. I knew I had some yellow 2-pack left over from spraying a bike, & that's usually fairly good at covering minor marks. (Chuckling) - Painting toy car bits with 2-pack using a full-size spray gun....

The finished chassis. Although you can still just see the marks in it, overall I'm pleased with the result for the lack of time, effort & money spent


Whilst waiting for paint to dry (Also ordered a ballrace kit, so waiting for that too) I moved on to some mechanical bits. Shocks next.
They were oozy.... I cleaned them.... yep still oozy, but now I could see the oil falling out under the effect of gravity. Suspect the seals may be poorly....

Remember me saying "Using the wrong oil damages the seals"? - this was what was inside the fronts, the rears were completely empty


If it looks, smells & tastes like Wilko 20/50 engine oil, it probably is....
Couldn't find any damage on the shock shafts, all the bits were present & correct, even the O-rings appeared to be unworn. I cleaned the O-rings again to get any oil residue off & did a test re-assembly with the original bits on one of the shocks & filled with silicone oil. Gave it some serious squidging & a couple of thumps, but I couldn't get it to leak, so I came to the conclusion the leaking was "Wrong oil" or possibly "Dry seals" related & put the other 3 shocks back together.
2 interesting things with these Mardave shocks - 1st is the method for having the right quantity of oil in them. It appears that only the lower cap is removable, but this has an O-ring seal & a slot up the side of its threads. The idea (I'm assuming) is to fill the body with oil, assemble all the bits, then fit the cap part-way, before the seal seals the assembly. Then, when you push the shaft inward, any excess oil is ejected through the slot. The slot is then sealed when you screw the cap home. 2nd point is the way the shaft seals are done - it's a double O-ring seal, which always work better, not because there's 2 of them, but because of the shape they go when squished together - they form almost a lip seal shape, which is a far better shape than round/eliptical for sealing on a shaft moving with linear action. Also interesting was the way the seals are held in place & pre-compressed, with a press-fit bush. I thought it was a pants idea until I realised that IF this bush were to come adrift, the downward/rest position of the damper piston would re-install it. Nice bit of thinking there Mr Mardave....
I don't know, but I suspect the shocks would have originally been supplied pre-built with the kit, there's certainly nothing about them in the build manual. Might be a pain if you ever had to rebuild them & were looking for pics of the internals...

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12331

Moving swiftly on.... I'd noticed that all the pivot pins on the car stick out, which was offending my eye & taking my skin off every time I handled the parts (The suspension & steering pivots are all held together with press-fit pins, left long I guess to make them easier to get hold of with pliers to remove). Have a measure, do some sums, then grind the pins to length, so they fit flush in their parts. Much nicer!

I had also originally contemplated replacing all the fasteners with phillips-headed screws - I can't stand slotted screws, what is it with the Brits & having to use them? Not a fan of Pozi-drive either (Pozi are like phillips, but have an extra, barely visible cross as well as the main one). "Gash level" goes no lower than phillips for me, & if I had my way, the only fasteners available would be these, hex, & hex socket. As for Torx, fantastic idea, but does anyone actually sell drivers that fit them properly? Ahem, moaning again then....
I put my world war 1 fastener anger aside & decided that it would probably be best to refit the original slotted screws, after all, the car wasn't going to be mine & my brother's perfectly capable of replacing them if he wants to &/or doesn't care that would affect the car's originality. Actually, the main reason was that the suspension top-links are held together with slotted M2.5 (What?!) machine screws & I couldn't see any good way of making any "Real" size shoulder screws happen. For any of you out there wondering, M2.5 is a non-preferred size (Like M14) & is mainly only ever used in specialised applications eg electronics. AND they're slotted, how offensive!

Next, I addressed the servo saver - I had the plastic army-bits, but no pivot, spring etc. Time to fire up the lathe then! Had a measure & studied the pic in the manual, then came up with the bits as below. Also made the wheel driving pins whilst I was at it.
(Yes, I just noticed there's a continuity issue with the pics - the servo saver is fitted in one of the earlier pics, before I'd made it...)



More continuity issues - you'll notice in the pic of the painted chassis that the body is missing most of its paint. This is because I'd already plonked it in brake fluid to fester when I was doing the chassis, but forgot to mention it!
The body was in brake fluid & getting a scrubbing every hour for about 3 days in the end, & that still didn't remove all of the paint! I got the last of it off using my more normal method of scraping with a scalpel blade.

However, during this lengthy paint-stripping exercise I noticed something interesting. Some of you will say "I knew that" but I've never seen/heard it mentioned before, so here goes - I'd read/heard people saying brake fluid clouds lexan shells, it gets worse the longer you leave the shell in the fluid. I've always had this in mind & been careful to not leave the shells long enough to damage them. In this case, I was less concerned as the shell was in a bit of a state & I'd already decided that if it didn't go according to plan, I'd try to source another. After 3 days in the fluid, yes it clouded, BUT only where the paint had been. The unpainted window areas were unaffected. Now, I know from previous experience that most scratches in lexan disappear when you paint it (Scratches & paint on the inside I mean). Knowing this, I'm going to say that the clouding is the result of attack by the solvents in the paint, & is there from the day you apply the paint, but you can't see it. The first time you see it is when you take the paint off. I suppose the proof would be to get an offcut of lexan from a new shell, plonk it in brake fluid & leave it, to see what happens.

The bearings took about a week to turn up, slower by 1st class than the rest of the car by 2nd class (I suspect the seller marked "dispatched" before he'd actually sent the bearings). Finally, I could get on with assembling everything, which took about an hour.
Everything fitted ok & worked as it should, but the quality of the mouldings & the amount "flash" on the parts was quite disappointing (I've been spoilt by Tamiya kits).

Gearbox bits look barely used (Good!) but I later re-discovered why I don't like ball diffs - it was tight but still slipping like it was full of eels. I tightened it as much as I dared (To the point it barely works as a diff) & now we have drive. This car still has its original spur gear, not the slipper clutch mod. More interesting stuff - the original spur & pinion are 32DP, but as Jonny found out, the slipper mod is a different pitch (48DP). There's a note stating this at the back of the manual. I'm guessing they did this to address the horrendous racket the gearbox makes when running the coarser gears!
I finished the gearbox by fitting a Parma 40deg motor, to give it some pep (My bro's a speed freak too).

I gathered together some radio & other electrical bits & installed that lot next so I could give it a run to see if there was anything I'd missed that might need attention.
Seriously tempted to get myself one now! Despite how gash, cheap & nasty looking these cars are, it goes really well & all works beautifully! (Other than the noisy geartrain & crap diff). I suspect it wants a larger pinion with that motor though as it's nearly "topping out" in the length of my front room & wheelies like a mad thing! (Far better than my M38 does!).

Next job, put some paint on & say "'kin Adam, why do I keep buying stuff from him?"
The discrepancy isn't so obvious in the pic, so I'll describe it - Paint can says "Cosmic glow green", that & the eye-wrenching colour of the label on the cap suggests it would be some sort of neon or day-glow or hazard warning flavour. The paint is "Toddler-friendly Lego green", "cosmic" must be some reference to inhalation of the fumes, & in my opinion is quite misleading.



Too late to take it off & start again, It'll have to do.
I next test-fitted the body to see if/what needed trimming to tidy up. Really should've done that sooner as it appeared the body had been quite poorly cut out or chopped about. In hindsight, I should've got a new body for it instead of putting effort into making good (Wasn't having a good day that day!). In the hope they'd take the eye off all the "blemishes", I found some graphics to make decals out of, & applied them. At last, a break! Looks considerably better for that!

A final proper test & it's ready to be boxed up & presented to my bro. Hope he likes it!
Hope he doesn't read this before I give it to him too!



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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12345

Whoa, too much reading for me there :P ;)

I did look at the pictures though - nice looking chassis, shame about the dull green paint ... I wonder if graphics in a brighter colour (yellow to match the chassis and/or orange)would lift it a bit?

:)

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12346

Nice thread, eddrick. And a very smart result! :y:
It's got the colours of my city - and that of the dudes Down Under of course... :cheer:

You wrote: However, during this lengthy paint-stripping exercise I noticed something interesting. Some of you will say "I knew that" but I've never seen/heard it mentioned before, so here goes - I'd read/heard people saying brake fluid clouds lexan shells, it gets worse the longer you leave the shell in the fluid. I've always had this in mind & been careful to not leave the shells long enough to damage them. In this case, I was less concerned as the shell was in a bit of a state & I'd already decided that if it didn't go according to plan, I'd try to source another. After 3 days in the fluid, yes it clouded, BUT only where the paint had been. The unpainted window areas were unaffected. Now, I know from previous experience that most scratches in lexan disappear when you paint it (Scratches & paint on the inside I mean). Knowing this, I'm going to say that the clouding is the result of attack by the solvents in the paint, & is there from the day you apply the paint, but you can't see it. The first time you see it is when you take the paint off. I suppose the proof would be to get an offcut of lexan from a new shell, plonk it in brake fluid & leave it, to see what happens.

I've drawn the same conclusion (apart from the paint solvent) from my latest lexan experiments.
Neither sodium hydroxide nor DOT 4 did any clouding on the windows.
I recall tamiya nut stopped using graffiti remover on his Avante shell not too long ago because it clouded.
Would be interesting to see what that does on a (clear and) unused bit...

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Last edit: by Edou.

Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12348

I thought the issue with brake fluid was that it weakened the plastic & you wouldn't know anything about it until you hit something & turned it into a jigsaw :cry:

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12357

Sorry for all the words guys, you know me....
I purposely didn't take loads of intermediate pics as there wasn't really anything interesting to show, but kinda wish I had now, to pad out all the black & white a bit!

I wasn't planning to smother it in stickers, it was a last-ditch attempt to take the eye off the dull colour & poor condition of the shell. The only sticky stuff I've got left is clear, so the colour had to be something dark that would still show over the dull green, either that or paint some white patches where the stickers would go (& that would've meant buying white lexan paint).
My brother loves it though (Delivered it this afternoon). It's a Cobra, it's mental fast, don't think he noticed what colour it was!

As for brake fluid turning lexan brittle, I haven't heard that one before, but that doesn't mean it doesn't make it brittle. Plastic is funny stuff when it comes to solvents & oils (& UV light) - some resist the solvent but get attacked by UV, others resist oils but get attacked by solvents.
Only way we're gonna find out for sure is to test some clean, new lexan with a variety of different chemicals etc to see what happens. There's lots of t'internet horror stories out there, but how many of them are accurate/true & not just rogue results from outside influence?

It could also be that the confusion is arising from shells that could be being made from materials other than polycarbonate. There's lots of materials out there nowadays that look, feel & behave like polycarb, but without its price tag. eg pop bottles used to be made from polycarb, but I'm sure that in recent years I've seen the PE recycling mark on them

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12359

Took me a bit but I read it all. ;)
I think I'll do some testing on the residual lexan I've got...
Knew that would come in handy at some point.

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12360

Well done Edou! How do I issue you with a gold star for reading?
I must admit, even I got bored reading it!

As for the testing, if you're in the mood, lob a lump of pop bottle in the fluid too.
(I need to also check what takeway tubs are made of, cos I know they cloud after having brake fluid in them)

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12361

eddrick wrote: ..
(I need to also check what takeway tubs are made of, cos I know they cloud after having brake fluid in them)


The ones I have are Polypropylene :)

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Re: Mardave Cobra - another quicky resto 7 years 3 months ago #12362

Did the read in a Sunday afternoon pace... I'm always curious to pick up some tricks from the stuff you're posting. :y:

I'll do a proper experiment - leave it in for a while and test the flexibility afterwards.
Maybe try some oven cleaner and graffiti remover too.
I must also have some modern Tamiya lexan somewhere...
That seems to have different properties from the vintage stuff.

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Last edit: by Edou.
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