Pre-wing (half tonner) F1's 1961-1965

[Kevan]

We have a new class in our club this year, one that's long overdue and that's what some call Pre-Wing and some call Half Tonners.

Whilst looking on the usual place for suitable cars and the online suppliers I had an idea what I was looking for then found a couple of old Airfix (Scaley) bodyshells I didn't know I had that are perfect, a '61 Cooper T53 and a '62 Lotus 25.

I had no design for these slim cigar shaped cars and had a brainwave to make an adjustable wheelbase two part chassis and started modifying the chassis design for a MRRC Chaparral 2C I was previously working on.

A few hours later Mk1 was printed and as I type four Mk2's with improvements are printing.

Whilst Mk1 has facility for unflanged ballraces in the pod with adjustable axle height - Mk2 has a centre pivot, reinforced rear part pf the pod, fixed height rear axle for flanged ballraces and larger front pocket for lead ballast.

As it stands, Mk1 chassis & body mount weighs 5.5g

This pod is for 050 (slimline) motors but could easily be modified for FC130 or FK130 motors

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[HO RacePro]

I like the two-part chassis with the piano wire coupling. I think that is a superior way to make a chassis length adjustable.

What material did you print the chassis in? I'm a bit concerned that the set screws will not maintain their holding power against the piano wire long term. My experience is some printed plastics will creep under stress, especially if that stress crosses build layers. I think this would be a good application for nylon.

You might want to experiment with lighter gauge piano wire. Some torsional flex in the chassis might be a good thing.

Ed Bianchi

[Kevan]

colorFabb XT-CF20 Carbon fiber filament...it's stiff!, I wouldn't say this was good material for adding torsional flex, I'd prefer to add torsional flex with a better material like wire.

That's 1mm piano wire, I was going to try 0.8mm and 0.6mm on the Mk2 with a centre pivot.

If you want 'permanent' then superglue in the holes underneath should be the belt & braces.

So far I'm more than happy with everything I've printed in this filament, minimal cleanup. I've tried Nylon before and won't be going back to it in a hurry. I've printed loads in PETG but this CF stuff is my current go-to.

[Kevan]

I measured the wire in the chassis, it's actually 0.9mm not 1mm. I've put 0.6mm in the Mk2 and that feels much better for the lengths used.

[Wet Coast Racer]

There must be a lot of slot car enthusiasts with really weird sounding pianos at home ...

[Speedhoppy]

THAT is a neat idea; done in a workmanlike manner. There are few of the older "cigar" shaped open wheel (F1 & Indy) cars in this scale; maybe this will get the market demand going for them!

[Kevan]

I'm up to Mk4 now...you can't beat printing it out for real-world bench testing

[Kevan]

I wasn't happy with the way the two parts interacted so added a centre pivot, this worked but I didn't like it as it was a bit flimsy so really beefed it up.

I went back to 0.9mm side springs but moved the securing grub screws right back and opened the hole up in the pod to allow for movement.

This version works well on the track so it was time to squeeze it into an ancient Scaley Lotus 25...an hour or so with a dremel and it fits great (gotta love the smell of 60's plastic burning away - not).

Guide/braid will be replaced with new, this is one I throw onto cars for testing. Rear axle needs trimming in length. Body extras required for more reality, rear exhausts, suspension links...and maybe painting green.

The front end needs a bit of a rethink for narrower cars, I have a resin '63 Scirocco SP and this wouldn't fit in that bodyshell.

This project has been on my mind for a couple of years now and I have lockdown to thank for getting it into reality.

This is almost as quick round my test track as my much wider open class Rally cars with steel chassis and 12mm wide tyres and has made me think about adding side pans for wider full bodies cars.

Running gear for this, 25k slimline motor, 7/27 gearing, max width across the outside of the tyres is 54mm and the rears are 9mm wide NSR Ultras and ground clearance is 2.4mm. (Tyres/width/ground clearance is for our club rules using the CSCRA general outline for this era 1961-1965 F1 cars). All in weight 62g (which includes the 12g of lead you can see).



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[f143]

The 9mm wide tyres are not to scale with the 1.5 litre cars, is that a club spec? good job with the chassis.
regards

[Kevan]

The 9mm wide tyres are not to scale with the 1.5 litre cars, is that a club spec? good job with the chassis.
regards

Read the last paragraph

[f143]

Doh, sorry Kevan, misty glasses.