Death Buggy Mk I repair

[jimmy221599968752]

all understandable, what i meant to say was the bracing itself would be twice a sstrong if welded not the whole thing , but i can see why you havent welded it now . You are most welcome to share the leading link design and make your sand yeti version of it, there are a couple of critical areas and the rest is up to your own skills, taste and ideas. The carkeek front end has lots of good up sides but the real benefits are felt when you go back to a rigid front after using the leading link for a while. Regarding your speed being lower with the carbon axle, your are possibly having a torque roll instead of acceleration due to the axle flex, personally unless i was racing id have a flexi axle, but for racing I still havent found what im looking for , U2 ?

[NZGene]

Didn't realise(or read past the fluffywhatsit) that huge hunk of square tubing is actually composite.

 

Carbon is pretty but unless you use a UV stable resin or give it a good UV stable clearcoat the resin will go brittle and degrade the laminate faster than steel. Especially where the sun is a little closer to the earth or the ozone a litte thinner. See if you can find any carbon masts in the local marina that aren't painted... mostly white.

 

Another thing to be careful of is point loads. While the plates that clamp either side of the axles spread the load. The bolts however, present a small surface in one axis that could crack the resin and propegate a failure in the laminate. Simply placing a spacer plate between the bolts and the axle will prevent this if there's room to do so.

[Giorgio]

Didn't realise(or read past the fluffywhatsit) that huge hunk of square tubing is actually composite.

 

Carbon is pretty but unless you use a UV stable resin or give it a good UV stable clearcoat the resin will go brittle and degrade the laminate faster than steel. Especially where the sun is a little closer to the earth or the ozone a litte thinner. See if you can find any carbon masts in the local marina that aren't painted... mostly white.

 

Another thing to be careful of is point loads. While the plates that clamp either side of the axles spread the load. The bolts however, present a small surface in one axis that could crack the resin and propegate a failure in the laminate. Simply placing a spacer plate between the bolts and the axle will prevent this if there's room to do so.

 

 

The axle was built as an experiment to have a starting point for what a suitable laminate could be. The fixing to the buggy is less than ideal, however in way of the bolts there is an extra patch of carbon and high density core. Because of the fixing arrangement the width of the axis was constrained to 40 mm , but future composite axix going into my new all carbon buggy will be taking full advantage of low density core material and probably be a 100 x 100 section tapering down to a 50 x 50 at the wheel attachement. As for the UV protection, again, it is a prototype and there is no point in painting before the construction is finalized. Next step will be to beef it up fore and aft to make it stiffer ant then it will get a generous coat of white paint ( or pink if Fluffywoo gets there before me!).

[jimmy221599968752]

good ideas guys keep em coming, at what point did you work out a whole buggy could be made this way Giorgio ? Im guessing you have come to that conclusion see link to the NZ creation s of carbon buggies, the 3 wheeler is the most successful one so far.. http://pic7.piczo.com/Popeyethewelder/?g=44377916&cr=7 , also a pic of that 4m jump with figlass rear axle breaking (later that day) but carkeek front end still happy

[Giorgio]

good ideas guys keep em coming, at what point did you work out a whole buggy could be made this way Giorgio ? Im guessing you have come to that conclusion see link to the NZ creation s of carbon buggies, the 3 wheeler is the most successful one so far.. http://pic7.piczo.com/Popeyethewelder/?g=44377916&cr=7 , also a pic of that 4m jump with figlass rear axle breaking (later that day) but carkeek front end still happy

 

I do composite for a living and it is what i have access to..so the call to make a buggy out of carbon was an easy one...i am useless with metal, plus it's heavy! i did see that one and if i was running over flat surfaces i would build it very similar, but over here we are after clearance for riding the dunes so the design is based around Sand Yeti DB1 with a few tweaks. I have the 3D model nearly finish i will post the rendering once it's done. i was not surprised to see that axle snapped, it was a very logical place for it to break, massive stress concentration plus if you are building out of carbon foam, why not make a big section axle with thin skins...that way you get massive stiffness for a very little weight penalty....

[jimmy221599968752]

it was more of a cheap experiment that Gannet (another Kiwi ) did , he has now gone with an egg shaped axle. My idea was to fill the insides with a polymer to get internal dampening !!!! I would love to see your design Giorgio If you want to make a leading link in carbon then say the word and ill help you start when i have finished with my Carkeek front end

[NZGene]

Not bashing it either. I like to see people pushing new ideas and I'm also in the early stages of building a composite axle. Just don't like to see a nice expensive piece of carbon laminate go to waste. ;-)

 

Grew up with a fibreglass itch due to a boatbuilder father who new the value of little hands that could reach places he couldn't. While composite design and construction isn't my primary means of income I have had a lot of experience fixing bad fabrication and shortcuts that in turn financially sponsored some of my other projects.

 

I simply prefer steel because I can chop, change and repair it and puts up with a tremendous amount of abuse. But I am planning on cross polinating some idease now I have a decent workshop and while I'm not lucky enough to own an autoclave or curing oven I still have a good vacuum pump and not scared of a wet layup either. )

[Giorgio]

it was more of a cheap experiment that Gannet (another Kiwi ) did , he has now gone with an egg shaped axle. My idea was to fill the insides with a polymer to get internal dampening !!!! I would love to see your design Giorgio If you want to make a leading link in carbon then say the word and ill help you start when i have finished with my Carkeek front end

 

One of the original ideas for the rear axle was to use a wood-carbon leafspring type construction. I have done it before for soemething completely different and using something like white ash would work a treat, but in the middle of the desert i seem to have trouble finding it, so for the moment carbon it is. One of the features of the buggy will be to have the real axle interchangable so i can test different layups. To get some form of dampening using e-glass instead of carbon would work. Maybe i'll do that nexta nd get Sand Yeti to try it for me!

[popeyethewelder]

This all sounds very exciting, composite sounds ideal in the desert, if it can take the stresses, you dont need the weight of a heavy buggy going up dunes as you don't have to go in straight lines...I look forward to the future creations

[NZGene]

My composite axle is a similar concept to a springboard borrowed from what we've built for some landyachts using construction techniques from some of the kiteboards we've built. I'd eventually build it using maple though the current prototype is just some treated ply offcuts from another project to find the profile with the right stiffness and best damping.

 

It is also part proof of concept for an idea I have for a kiteboat frame but that will have to wait till next year some time.

[Sand-Yeti]

Didn't realise(or read past the fluffywhatsit) that huge hunk of square tubing is actually composite.

 

Carbon is pretty but unless you use a UV stable resin or give it a good UV stable clearcoat the resin will go brittle and degrade the laminate faster than steel. Especially where the sun is a little closer to the earth or the ozone a litte thinner. See if you can find any carbon masts in the local marina that aren't painted... mostly white.

 

Another thing to be careful of is point loads. While the plates that clamp either side of the axles spread the load. The bolts however, present a small surface in one axis that could crack the resin and propegate a failure in the laminate. Simply placing a spacer plate between the bolts and the axle will prevent this if there's room to do so.

 

Had you read further, you would have noticed my comment on the affects of UV on the composite axle.

However, as Giorgio pointed out, this is just an axle that he made for test purposes. It was only finished on the morning of the day that I tried it out.

Knowing nothing about composites, I discussed with Girogio how good this stuff is in terms of fatigue life. He replied that it wasn't an issue but rather we should be more concerned about the affects of UV. I asked if we needed some special paint to protect the composite against UV light & he said that just good old enamel paint was good enough.

 

He gave me a piece of the core material so I could see what it looks like. It was as light as a feather and looks rather like a Crunchie bar with the chocolate removed. i.e. same colour or slightly lighter yellow and similar sort of grain structure but obviously not good for sucking and could not be broken in the hands.

 

As Giorgio later mentioned the fixing to the DB-1 was far from ideal and we had discussed that as well. My buggies were available to test the comp. axle without making and mods to the steel fabrication.

 

He used denser core material in the clamping areas and additional layer or layers of carbon around the core. He later mentioned that on this thread.

I bought new Allen bolts just for this test axle where only the end of the bolt is threaded. We wanted to ensure thread edges wouldn't stick into the comp. axle.

We had a laugh when tightening up the these clamping Bolts both agreeing that they should not be overtorqued mentioning our mutual friend Sir Bolts. We used locknuts just in case we hadn't applied sufficient torque to ensure axle didn't drop off while I was blatting along.

 

I'm alway winding up Sir Bolts for being heavy handed on the spanners & tearing up bolts with regularity due to overtorquing. He will tell you that he doesn't. We call him Sir Bolts because I can't pronounce his Hungarian name but it sounds something like that.

As it turns out the name Bolts is quite appropiate for him in view of what he does to wreck bolts.

 

Giorgio could make the axle up where he works and I think the most expensive part was his time. If you knew what he does in his line of business designing & building some of the fastest Class I racing boats in the world you would feel confident that he knows what he is doing.

I wouldn't risk bouncing around at 60+ kph or fly over dunes in my buggy with his test axles if I didn't have confidence in what he was doing.