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Composite leaf spring

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chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Just looked at the C50 wheels, the hub looks narrower than the ones I'm looking at, but the bearings are recessed less on the C50's. I might need about a 1" spacer to keep the suspension clear of the hub, that's a detail to be sorted, as long as the test blades are somewhere near they'll give worthwhile info. I'll play with polyester initially as it's what I've got, then probably move on to epoxy, for the final job.

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chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Thanks for the dimensions Victor, at least I know I’m in the right region with my guesstimate. I'm going to do some trial blades, I can then clamp them at various lengths and do some load against deflection measurements. It'll give me a feel for what's needed when I do come to mould some springs.

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Well I made a first test blade, 50mm wide by 4.5mm thick, six layers of 300gsm mat, polyester resin. My first impression was that it was surprisingly flexible. I'm used to single 300gsm hull mouldings with a second strip reinforcing the topsides, of course they have form stiffness, being compound curves for the most part. Anyway I ran some quick tests yesterday, and I've attached the results. I need to make up something three or four times the thickness, and rerun the tests, but it's a start.

The other two photos are of one of the hulls I produce, so as you can see flat is not something I’m used to moulding.



Edited 1 time(s). Last edit at 2017-03-01 03:44 AM by chrisenamels.

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Graph 50mm x 4.5mm 6 x 300gsm.pdf    15 KB

1384100582256.jpg    16.3 KB
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1384100572507.jpg    15.4 KB
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Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
I would not be using CSM! I don't think it's the correct material.

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Agreed Rhys, it's what I have lots of, just to get a feel for the sort of layup needed, before I look at either cloth or roving, both of which I'd have to buy. I realise directional reinforcing will be stiffer, but not inclined to spend as I'm still wavering between single wishbone and sliding pillar.

Chris

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Change of plan Rhys, just come across some 6" cloth tape from the dim and distant past, so I'll do my next leaf with that. May also try a csm core with cloth skins, just out of curiosity.

Chris

Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
I think it's great that you're trying something different for a Cyclekart Chris.
We are all to dependent on the limited supply and over priced spring sources
that exist at present. Single leaf 24" steel springs are priced for times as much
as they should be, Kudo's to anyone that's willing to experiment and develop
a method to build a substitute in the home shop.

Denny Graham
Sandwich, IL

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chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Denny,

I'm just one of those who are curious about alternative ways of doing things. It's Stephen G with the composite springs that he made for his pedal car that set me off. He posted details on the first page of this topic, his posts on the build are here: http://www.cyclekartclub.com/phorum/read.php?5,20307,21984#msg-21984.

As you say if the information can be assembled, then anyone can make their own spring for something like £10, and tune it for their needs.

Chris

Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
Absolutely agree it's a great thing to experiment. I will ask my son if he can do some calcs for comparison for lay up. What would make it easier if someone has the width and thickness of the buggy springs which we know work as a start point. Please no trailer ones, I know they don't work well.
I suspect that the ones "Stegla" did for the pedal car would give a good lead on laminate.
Laminate I would think that ideally uni with a cloth back might be the ultimate until carbon or something similar was used.
I made some model hulls years back from very light Kevlar/aramid fibre. Total fail as there was zero panel stiffnes which I gained by a single layer of 225 CSM, it became very strong, but saved very little weight.
Congratulations on those clinker (lapstrake) hulls Chris, it doesn't get any more difficult than those and you look to have done an outstanding job on them.

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chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Rhys,

The buggy seat springs look to be 22" eye to eye, 1 1/4" or 1 1/2" wide, but no thickness given on the site I looked at.

I started off laminating in cloth to keep the weight down, until I realised that I could use mat, and still produce lighter hulls than the competition. Thanks for the compliment on the hulls, getting the finish isn't actually that difficult, solid plug with the "planking" applied over it before taking the mould off. The keel is solid slush moulded glassfibre, which is part of the reason my layups are lighter than the competition, the other part is that their layups are far heavier than needed.

stegla Stephen G
Guernsey, Channel Islands, UK   GBR
I think that if chopped strand mat and polyester resin does the job... then go with it.

We're not talking aerospace or F1 racing cars here, so a less than optimum component weightwise and strengthwise will be just fine.

Carbon fibre looks sexy.......... just adds bling imho.



Here's how I do my layup, with a winding jig.

The wooden jig is long enough to account for the bow in the spring. Metal tubes are slid on at either end for the shackles

I wet-out the glass tape on the white plastic sheet. The wooden jig spins as I wind on the laminations. Just slip off and into the mould.


Ideally a two man operation........... one wetting out and one winding. It was easy enough single-handed however.

Steve



Edited 1 time(s). Last edit at 2017-03-02 04:31 AM by stegla.


Attachments:
DSCF1951.JPG    47.2 KB
DSCF1951.JPG

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Steve,

I'll continue to play with CSM, but as I've found the cloth tape, which I knew was here somewhere, I'll try that too, since I've got no other use for it. As I'll be laminating for a week or so, in the run up to the Coalville Model Boat Show, I can get some blades done at the same time.

As you say even if it's not ideal, if it does the job, and it's cheap, available, and easy to use, its worth persevering.

Chris

bluesdocbob Avatar
bluesdocbob Bob Paterson
Darlington, Victoria, Australia   AUS
interesting concept how would it work with the use of the F/glass and add in several lengths of
a nylon or similar strips or rods to make various tensions. or even several individual layers.....
Cheer Bob

chrisenamels Avatar
chrisenamels Silver Member Chris Brown
Llangadog, Carmarthenshire, UK   GBR
Bob,

The problem with nylon is that the resins won't bond well to it, it would also increase the flexibility of the spring, which from the little I've done so far isn't needed. Varying the width and thickness of the blade to get the desired stiffness is simpler, as you're inly dealing with one material. Others may have different views, feel free to chime in, discussion is what it's all about.

Chris

Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
In reply to # 22726 by chrisenamels Bob,

The problem with nylon is that the resins won't bond well to it, it would also increase the flexibility of the spring, which from the little I've done so far isn't needed. Varying the width and thickness of the blade to get the desired stiffness is simpler, as you're inly dealing with one material. Others may have different views, feel free to chime in, discussion is what it's all about.

Chris

That was precisely my reaction Chris. The thickness is the one that adds more to stiffness than width. I am sure that Denny has the comparison figures. I have just been handed a "Technical Pocket Guide" from son the suspension designer at Jag/Land Rover. When I figure out how to read it I'm sure the numbers will be in there somewhere smiling smiley

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