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#Post#: 15463--------------------------------------------------
Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 2, 2026, 11:07 am
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Hi everyone, I am having a spot of bother understanding what is
going on in this design. I get the short/long parallel
wishbones on a backbone chassis with transverse leaf springing
but I can't identify any dampers - unless the steering
incorporates some kind of sliding friction pillar? Also, what
are the little cup-type things at the in- board ends of what I
assume are the brake actuators?
Separate question but how would I deal with the spring/damper
for a kart, staying as true as possible (wishbones on a backbone
chassis) ?
HTML https://auta5p.eu/muzea/museo_nazionale_auto_2024/mauto_110.php
#Post#: 15469--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: Ade Colmar
Date: September 5, 2026, 3:18 am
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An interesting chassis design and well worth some thought. :)
Independent front and rear suspension was a rare thing in 1924!
As for damping, I don't see any separate damper/shock absorbers
either. However, with that many leaves in the cart springs I
imagine there would be significant friction between the leaves
giving some damping. I have no idea whether that was intented by
the designer.
Before you get stuck into deciding on your options it is well
worth making yourself familiar with the detailed regulations in
the full handbook. Damping is allowed, but it must be period
and appropriate. In practice most builders don't bother in the
interests of chasing simplicity, plus any suspension travel is
minimal anyway. If you watch cyclekarts going around a track a
speed, they seem none the worse for the lack of damping.
One thing I would note about your 1924 Aosta chassis design is
that it could very easily lead to a high seat location and
therefore a high centre of gravity. Cyclekarts rolling have
been the biggest risk we have faced to date. I would recommend
you consider an inspiration car that lends itself to keeping the
centre of gravity low.
#Post#: 15470--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 5, 2026, 9:44 am
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Thanks Ade, how high above the axles is seen as a high centre of
gravity? The wishbone set up means the chassis top will be 2 or
3 inches above the axles
#Post#: 15471--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 5, 2026, 4:39 pm
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I've been spending time looking at the photo and it seems like
the suspension is built on separate subframes, the backbone
being wider and more shallow. The designer also seems to have
dropped the engine through the chassis top rail, using a box of
some sort to strengthen it. Not sure. The shadow below the
chassis appears to be wider at the front than at the back so the
chassis may not be as straight as it looks, but that might be
wishful thinking on my part.
#Post#: 15472--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: Jimr1999
Date: September 6, 2026, 12:38 am
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I believe it was designed as a light car - top speed low 40's -
and of that era, possibly without much damping. See a 1922 G.N
below for comparison - G.N specials are still raced today with
the VSCC. You will get a little damping if you have several
layers of spring, but it would be super stiff.
As Ade has pointed out, a low centre of gravity (CoG) on
cyclekarts is a major safety consideration. My first Cyclekart
was a BSA three wheeler, I started with a spine chassis and
monococque ply and timber design dropping the centre of the
spine to try and achieve a lower CoG, but still with the seat a
good 6" off the deck. My front suspension is after the BSA so
not too dissimilar to the arrangement of the San Giusto. I have
had that on two wheels more often than I would like and it laps
at 3/4 the speed of anything else on the track on a good day. A
cyclekart I reserve for display and low speed events now.
Most of the weight of a cyclekart is in a single component - the
driver- Get your bum as low as you can whilst retaining a little
ground clearance. For reference, my Auto union has 2 1/2" under
the floor pan and that grounds out occasionally at events, My
G.N has 3" and so far that does not.
If you are determined to produce a backbone chassis design, be
content with a beautiful recreation of a marque you have an
interest in. If you want a quicker cyclekart, keep a low CoG and
produce a chassis that goes around your body but make the visual
appearance similar to the original marque. The most important
rule after building a safe to drive cyclekart is to make it look
good.
Build on and have fun.
JimR
#Post#: 15475--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 6, 2026, 3:49 am
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Thanks Jim, that's exactly the information I needed, your BSA
sounds like exactly the way I was thinking of going but getting
the seat down to maybe 4" off the floor would be a significant
challenge with a backbone. I reckoned on getting maybe 8" from
seat base to deck, and that seems like a no-no.
#Post#: 15479--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: Jimr1999
Date: September 7, 2026, 1:15 am
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You could try to build the main frame like a lozenge and add the
spine fore and aft, that may work
JimR
#Post#: 15481--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 7, 2026, 2:20 am
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That is a really good idea, definitely worth looking at. One
option I came up with last night, looking at how the maker
flared the chassis out towards the centre of the car, and how
the car appears to be pointy at each end with slab sides, was a
plywood monocoque with the chassis being a double skin floor.
That way I could incorporate the seat inside the chassis rails,
bum on floor; place the engine in a box frame with top rails,
and mount the suspension on hard points . Mounting the pedals
could be interesting though.
#Post#: 15482--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 7, 2026, 9:31 am
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Wasn't easy but I finally found a photo of a stripped down
version. How cute is that?!
#Post#: 15483--------------------------------------------------
Re: Need help interpreting chassis photo
DIR By: stuckinthemud
Date: September 7, 2026, 11:32 am
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Very different from this one. The archive suggests two
different chassis, the early one, and the second, simpler
(cheaper to make) one. The early one almost looks like a
development mule, cranked forward section running from above the
front suspension to low down for the cabin, with a pair of big
box sections for seat and engine.
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