hi, anyone know if carbon fiber composite (or carbon & kevlar etc) would be usable as engine plates for a motorcycle … (triumph t140 in a norton featherbed)
while i’m sure i could make them easily enough i’m unsure if they’d flex too much (they’d be the only things holding the engine in place - 4 plates at the rear, 2 at the front & a head steady) or what thickness i’d need to use (original triumph engine plates are about 6mm mild steel, apparently 1/4" alloy is used commonly)
thanks (i hope)
j0hn
Carbon - epoxy laminate has at least a comparible stiffness with steel, so that should not be the problem. I have no idea of the heat involved, so check that out. Use an epoxy that can withstand the heat.
As for vibration resistance, it should be OK. You could expect some more vibrations in the frame.
Should you expect less vibrations? I thought that was a property of using carbon…good for rackets, handlebars, etc.
no issues with carbon plates for motorcycle… my father in law is a circle track runner and there is a few people with it… i would suggest something more heat resistance like vinyl ester resin over epoxy… it makes infusion easier too… its what most hoods on cars are made from unless you plan to do a dry carbon setup which would take heating up prepreg carbon fiber
excellent … thanks very much for the info
Make or order a flat plate and start fabricating. The carbon will be just fine
does anyone know what thickness would be needed (playing it safe) bearing in mind it will be taking the full weight & twisting forces of the engine … the engine weighs about 70kgs (150 lbs) & there is no ‘central spindle’… just worried that plates would flex & let engine jump around.
again just carbon with vinyl ester not carbon/kevlar ?(8mm bolts go through the plates about 8mm from the edge of the plates)
found a pic please see attached
to my (admittedly very limited) understanding carbon flexes instead of snapping … my worry being it might let the whole thing jump about instead of holding it in place… rubber mounting has been tried in the past but not what i’m aiming for (unless movement is negligible … some of the plates are quite long)
it looks pretty thick… as mentioned above the resin will make it flex before it breaks… the real question is how much flex is too much… specially with riding and characteristics of a bike…
suggestion i have is maybe try 8 layers 8oz twill… (i think 5.7 oz twill will be too thin) with a core in the middle so 4 layers then core material then 4 more layers… i would do the parts that might see the first jolt of torque from the engine and see how they hold up… do a few trial runs stuff like that… if all is well then i would proceed with the rest… if there still is too much flex i would add a layer to each side… the main key is having the core material since that will give it its rigidness…
its all about trial and error… so good luck on the product… post pictures when its done
apparently flax fibre has some pretty good vibration dampening characteristics. Never did any tests with the stuff, so I can’t say how much the dampening actually is.
When comparing the properties between a steel bracket or a carbon one you have to know what criteria you are using to compare them. Are we talking equal weight, equal thickness, what?
Carbon has low strain properties compared to most structural steels. This means that steel can deform much further before failing than carbon can.
Steel is more stiff (Youngs modulus = 150 GPa or higher) than woven standard modulus carbon (70 GPa - Vf 60%) if the cross-section area is equal = equal thickness.
You could make a carbon one, or even fiberglass, that is both stronger and stiffer than your present steel brackets but the laminate will have to be thicker than your present steel ones…it will still be lighter.
Since bolts go through the laminate any core material will need to withstand the compression force unless inserts are incorporated into the layup. You need a resin that can facilitate a good inter-laminar bond so it doesn’t delaminate overtime due to vibration. I would personally use a high temp epoxy resin that is toughened so it’s not so brittle. The highest Tg that your going to get with VE is around 200F. A high temp epoxy can get you to 450F but you’ll have to cure it properly with an oven.
In the end I would just get steel ones. Great solvent resistance, heat resistance, and strain properties if the bike gets laid over.
I personally wouldn’t use kevlar because of it’s propensity to delaminate over time with vibration and recurring stress. You can use a kevlar/carbon hybrid to improve things but a full carbon laminate will still perform better.
Are your trying to save a few ounces in a racing situation? Why not just use steel? I like composites as much as anyone here but sometimes steel is just a more practical solution.
And if weight is critical, titanium is a valid option as well.