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#Post#: 5469--------------------------------------------------
HDPE springs
DIR By: guest274
Date: February 13, 2022, 7:45 am
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I got some Pro jump springs rated at 35kilos. I mentioned in
another post that there didn't seem to be any deflection when I
applied pressure. I am still wondering how effective they can be
as suspension. I have used HDPE for things and thought it might
be alright to make some springs from it. I cut some strips about
2" wide from a plastic drum. Cut them so there was 24" from end
to end in a straight line which gave an arch of roughly 5". As
you can see in the photo, I clamped two stops 24" apart and put
the strips between them. They were not fastened together in any
way(like a metal leaf spring). There was a fair amount of
resistance when I pressed down on the middle. I am thinking that
with some tinkering, they may be good enough to be used on a CK.
Your opinions will be greatly received.
#Post#: 5477--------------------------------------------------
Re: HDPE springs
DIR By: RhysN
Date: February 14, 2022, 1:09 am
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I do love it when the box for thinking gets thrown out :)
From a different method, and also bear in mind that some folks
have vastly differing ideas on how much a cyclekart will weigh,
if you are thinking of one at about 125kg all up, then if you
were to work on about 50mm deflection with say 40 kg in the
middle and one end free to move then you are well inside the
ballpark. How about using the clamp in the middle to hold the
"spring pack" together. (not clamped to the bench)
Please advise how this goes, as you may have just given an
answer to an issue I have to resolve.
#Post#: 5479--------------------------------------------------
Re: HDPE springs
DIR By: guest274
Date: February 14, 2022, 2:31 am
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I'm a great believer in "if you don't try you'll never know".
All I have done up to now is what you see in the photo. I was
thinking of holding the leaves together in the same way as
"normal" leaves. Or drill some slots through them and use nuts
and bolts instead, As for holding them to the chassis, maybe
heat the ends and bend them parallel to the chassis and then
some U bolts or something similar. What do you think?
#Post#: 5486--------------------------------------------------
Re: HDPE springs
DIR By: RhysN
Date: February 14, 2022, 6:15 am
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As you are experimenting I would like to gain some knowledge
from your efforts. Almost all the leaf springs I know have a
centre bolt which locates them on the axle, and also holds the
leaves together. There are also the clips that wrap around to
keep the leaves in line. It's not uncommon to have one end bent
as you say , I know that as a slipper spring, and in some cases
is very useful. (Parry Thomas used them on almost everything,
including the Leyland Eight) the other end usually has an eye,
but if you were to add some axle location why not have slippers
both ends? Standard leaf springs are a cheap solution on full
size cars and provide both location and springing.
There's no reason why these could not be wrapped with "string"
as was the case on many cars of the era, also adds a bit of
friction between the leaves, but still had that centre bolt.
#Post#: 5504--------------------------------------------------
Re: HDPE springs
DIR By: David F-R
Date: February 15, 2022, 4:19 am
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Just wondering -
HDPE sheet is fairly cheap and readily available (1000 x 100 x 8
=£13.50).
It can be warmed with a hot air gun and formed over a
semi-elliptical wood mould.
Would this do the business for CK springs? Perhaps with one or
two eyes bolted to the ends? One leaf or two thinner ones?
Just wondering?
#Post#: 5505--------------------------------------------------
Re: HDPE springs
DIR By: RhysN
Date: February 15, 2022, 4:25 am
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I'm wondering too! I want to do some experimenting to see what
the flex is like.
#Post#: 5506--------------------------------------------------
Re: HDPE springs
DIR By: guest274
Date: February 15, 2022, 6:22 am
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Buying HDPE? I have never considered that. I daresay it is
consistently flat as opposed to strips cut from a 55 gallon
drum, but at least they already have the curve. At £5 for a drum
I can make loads of springs and other bits for a kart. The way I
see it working is that the leaves are fastened together with
nuts and bolts through slots rather than just a hole to allow
some movement and both ends of the spring are fixed to the
chassis to prevent any lateral movement, only downwards/upwards
towards the chassis. I have bolted mine and placed them between
two stops as in the picture. They flex but not a lot. A hole
could drilled through where they meet the axle to prevent them
moving. I am not at the stage of attaching springs, but I see no
reason why they should not work.
#Post#: 5507--------------------------------------------------
Re: HDPE springs
DIR By: chrisenamels
Date: February 15, 2022, 7:02 am
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Watching with interest, be easier to do than the grp ones that I
was tempted to make.
#Post#: 5508--------------------------------------------------
Re: HDPE springs
DIR By: David F-R
Date: February 15, 2022, 7:12 am
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You clearly have a supply of drums readily available, not so for
me. Also, I want to try with a single leaf so I've ordered 8mm
need material, just enough to play with and make a pair of
springs if it works. It will all add to the communal pool of
knowledge for us to share. I'll let you know how I get on.
And then, more wondering, there is the glass, carbon, resin
composite to consider - as per archery bow maybe. All very shed
friendly technology.
#Post#: 5510--------------------------------------------------
Re: HDPE springs
DIR By: chrisenamels
Date: February 15, 2022, 8:41 am
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Just looked on Facebook marketplace, found some drums in
Carmarthen for £3 each, hopefully I'll pick one up on Thursday
and do some testing.
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