ESE's works engine tuner

[F5 Dave]

Trials bikes run tubeless rears at about 3psi, sadly not in rim sizes you'll want to use.

[F5 Dave]

Crank stuffers; What type of plastic do manufacturers use for crank webs fillers?, CRs for example. Needs to cope with a bit of heat, but also not deform enough to make the retaining screws loose. Doesn't look opaque like Acetal. More translucent like some Nylons, but nylon is pretty soft.

[dinamik2t]

Crank stuffers; What type of plastic do manufacturers use for crank webs fillers?, CRs for example. Needs to cope with a bit of heat, but also not deform enough to make the retaining screws loose. Doesn't look opaque like Acetal. More translucent like some Nylons, but nylon is pretty soft.

I think it's Teflon!

[FastFred]

Crank stuffers; What type of plastic do manufacturers use for crank webs fillers?, CRs for example. Needs to cope with a bit of heat, but also not deform enough to make the retaining screws loose. Doesn't look opaque like Acetal. More translucent like some Nylons, but nylon is pretty soft.

PVDF perhaps, just guessing though, it would be interesting to know for sure.

PVDF looks like Teflon, but cheaper and is used when parts need to be moulded and have similar properties to Teflon.

Wiki

Polyvinylidene fluoride, or polyvinylidene difluoride (PVDF) is a highly non-reactive and pure thermoplastic fluoropolymer produced by the polymerization of vinylidene difluoride.

PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat.

It has a low density (1.78) and low cost compared to the other fluoropolymers. It is available as piping products, sheet, tubing, films, plate and an insulator for premium wire. It can be injected, molded or welded and is commonly used in the chemical, semiconductor, medical and defense industries, as well as in lithium ion batteries. It is also available as a crosslinked closed cell foam, used increasingly in aviation and aerospace applications.

And

""Hylar® 301F PVDF is a versatile engineering plastic with a balance of physical properties that qualify it for high performance service in a wide range of applications.""

http://www.solvayplastics.com/sites/...ylar_PVDF.aspx

[Haufen]

Crank stuffers; What type of plastic do manufacturers use for crank webs fillers?, CRs for example. Needs to cope with a bit of heat, but also not deform enough to make the retaining screws loose. Doesn't look opaque like Acetal. More translucent like some Nylons, but nylon is pretty soft.

When I made some stuffers for a crank a couple of years ago, I think I chose POM. Unfortunately, I have never run that crank, yet. But it was fun making the inserts.

[Frits Overmars]

Crank stuffers? An Aprilia RSW125 has a TDC crankcase volume of 650 cc. An RSA125 has 675 cc and a bit more power. See where this is going?

[F5 Dave]

yes, but where in the crankcase was the volume concentrated?

if for example one had the 'compromise' of having a clearance over the web to case of 1mm or above to limit shear, but otherwise had as little volume in the web area, - and more area underneath the transfers to draw easily from; -would that be a perceived advantage, rather than have to pull from the violently rotating webs?

Indeed incomplete webs are effectively paddles thrashing more air about in an already turbulent area. Just thinking about the comment of the incoming gasses & the rotation of the crank web comments as well.

Might be totally wasting my time, but I'm sure there are people who have done this sort of analysis. Ohh look. We have smart researchy people in attendance.

[TZ350]

Here is a pic of cranks for Aprilia 250.
Full circle, full width, plenty of Mallory, high inertia, very low in cycle speed variation, lots of power and overev - why isnt your crank like this??

Crank stuffers? An Aprilia RSW125 has a TDC crankcase volume of 650 cc. An RSA125 has 675 cc and a bit more power. See where this is going?

Suzuki GP 125 crank with the balance holes plugged.

If the Aprilia 125 crank doesn't have these balance holes and is like the Aprilia 250 that Wob posted. Would it be better to stuff the Suzukis balance holes then get volume by increasing the crank case size or doesn't it matter about part of the case volume being in the rapidly rotating crank?

[Farmaken]

Isn`t the big end also a fairly effective paddle that we cannot do away with ??

How much difference would partial webs and unfilled balance holes really make to crankcase turbulence given that other piece of steel wizzing up and down and around

Buggered if I Know

[Yow Ling]

yes, but where in the crankcase was the volume concentrated?

if for example one had the 'compromise' of having a clearance over the web to case of 1mm or above to limit shear, but otherwise had as little volume in the web area, - and more area underneath the transfers to draw easily from; -would that be a perceived advantage, rather than have to pull from the violently rotating webs?

Indeed incomplete webs are effectively paddles thrashing more air about in an already turbulent area. Just thinking about the comment of the incoming gasses & the rotation of the crank web comments as well.

Might be totally wasting my time, but I'm sure there are people who have done this sort of analysis. Ohh look. We have smart researchy people in attendance.

Dont worry I not one of them, why would the mixture come from round the spinning cranky things , there is nothing going on there to pump anything, my mental moddeling just has a blob of gas mix under and around the piston that gently bumps the mixture waiting in the transfers into the cylinder. With what frits says about the rsa and rsw ccv's , would indicate that the pipe is more involved than the crankcase compression in filling the cylinder

In saying that Wobbly is using some aluminium stuffers on my crank, i think this has to do with the paddle problem.

in this thread is the stuffing http://www.kiwibiker.co.nz/forums/sh...post1130142699

[F5 Dave]

I'm doing my very best to make a decent reedblock intake on the MB engine, but it is still a compromise & the lower flow will hit the webs so I can't make web covers like on Yowlings engine, so just trying to minimise turbulence in that flow area.

[F5 Dave]

Hmm, pdvf isn't the most common beastie.

[twotempi]

What about old-fashion cork araldited in the crank web holes.

And you get to drink the wine as well. ( Hickkk !)

Try it and see if you can detect a difference on the dyno.

If you can't detect an increase then don't bother doing anything more.

A lot less work AND if it comes loose it will not lock the engine up.

The easiest and cheapest way to save weight on a small bike is to buy a pair of running shoes.

As Fritz said DON'T. repeat DON'T use tubeless tyres on rims that don't have the retainer bead/hump. Or could you please leave your bike to me in your will. I reckon a 50/50 chance of collecting it!!!!

[F5 Dave]

cork won't stay in the web cut outs (incomplete web). I was intending on trying it, but clearly Frits for example will likely know if it is a waste of time, but I'm assuming the RSA cranks were full circle for a reason. I don't have a heap of time to try everything I want, so very happy to learn without having to make every mistake myself.

[husaberg]

cork won't stay in the web cut outs (incomplete web). I was intending on trying it, but clearly Frits for example will likely know if it is a waste of time, but I'm assuming the RSA cranks were full circle for a reason. I don't have a heap of time to try everything I want, so very happy to learn without having to make every mistake myself.

I have seen some stuff in another forum where some stuffers used by Yamaha have melted into the big end with well the result you would expect.
There are replacement ones on Ebay as well
http://www.ebay.com/itm/ws/eBayISAPI...vip=true&rt=nc

Having said that i have seen epoxy (like devcon) used for porkchop old Villiers shitters.
They used to drill in screws then the epoxy over it to attach it more securely to the webs.
As well as hollow section stuffers to fill in half circle cranks on other Villiers as well welded or brazed together and too the crank.