how does it shorten the life of the pistons ?

never really looked into engine building

matt

 

if the skirt is shorter it allows the piston to rock in the bores and then wears away the material.
A piston with a long skirt will stay vertical under all conditions whereas the shorter one will rotate and rock around the small end bearing and put a little more stress there aswell

 

how much clearance is there usually between piston and the bore ?

 

Not a dig or anything mate, but if the piston is rocking as you say would it cause the engine to rattle?
Genuine question.

 

so what are the benifits of a shorter skirt?

just simply less weight?

or is there alot more to it?

 

Its normally the small end that rattles, the piston moving in the bores is a very small amount but enough to make manufacturers have long skirts to make the engine last, with a short skirt the pistons may only last 10,000 miles

Clearance between the piston and bore is probable 20 tho either side

 

less weight therefore less stress on the bearings when the motor is spinning at 8000 revs and changing direction at the end of each stroke.

Formula 1 cars have pistons that are basically a gudgeon pin and one ring only, very small but VERY light hence they can rev to 18,000 plus

 

yeah thought that was the only reason.

As with all high powered engine build, everything comes at a price, every is a compremise. You cant have the best of both worlds

 

im sure i had my block honed by 3.5 thou... surely 20 thou is going to be a bit tight isnt it?
i have accralite pistons in my engine.. and they rattle when cold (because they are a true forged piston) this i realise will wear the bore more significantly that and the fact they use a central gudeon pin however after removing the head (to replace with stage 3 jobbie) the bores are PERFECT this is after only 2k miles though...

 

An aluminium piston will not wear a steal liner away, it will be the piston that is the sacraficial offering, thats 20 thou either side, a mm overall and that is not on the thrust side

 

nice.................... all white cars in the above sigs

 

i'll join in on the white cars in sig bit....cant offer any knowledge on engine building though i'm afraid

 

Sorted..... how many white car sigs can we get in one post

 

get some piccys up simon

 

Ahhhhhhhhhhhh a black car sig Gus!!!
What do you want pics of matey

 

I don't know much about four strokes but technology today (as I'm a 2 stroke tuner & my engines rev to 21.000 rpm) has no one thought of ceramicing bores

 

Karting
Want to buy a Wright 100cc National Kart with a KTM motor?

Is the ceramic bore not to do with the fact that there is no oil pump in a 2 stroke and the fuel\oil mix causes things to run much hotter?

 

all the biuld simon

 

cossy abuser ther is not an engine in 100 nat called KTM & I don't wish to buy & I think you will find you are talking about nickelsil, as I hire all my engines out anyway for British championships(thank you).

 

Cossy abuser, are you talking about a TKM engine? which is a piston port with carb at the front

 

fair enough, just put your name with karting and tried to add 2 and 2 but got 5

Ceramics are used in Formula 1 alot but is a very expensive process on a multi cylinder motor, but then they don't bother with valve springs either which is way out of reach of most normal engine manufacturers

Gus
Will take some pics of the build tomorrow, but not of the motor as it is top secret with some ideas I am trying, if it works i will let you know in about a month when the motor gets Dyno'd , if it doesn't work you will never know

 

yes but carb is on the side

 

I had williams formula 1 down on my dyno, they coat their exhausts, it doesn't work on 2 strokes

 

Very old TKM, KA100, max rpm 16000

 

sound like you've had fun, my old man does alot of engine work with high speed cameras in Korean Car Companys, not quite F1 but he gets to see some interesting stuff,

 

Nice to speak to you cossy abuser.

 

you too!
speak again in the future I hope

 

God, that kart brings back some memories! I had a Wright chassis years ago!

 

God, that kart brings back some memories! I had a Wright chassis years ago!
RichardPON, you must be an old git as well then, just like me.

 

Nope, only 25, but been karting since I was 10.

Haven't used the karts in a while, but one of them is rising in value by the day

 

Was you any good?

 

I hope that's not 20 thousands of an inch

Mark

 

I hope that's not 20 thousands of an inch, otherwise it will rattle. You will get piston slap.

 

I used to be very quick. Motorsport would have been a career for me if I hadn't had a very serious accident a Tilbury and ended up in hospital for a long time!

 

Did you hit the fence? What class were you in?

 

Back in those days, I used to run Junior Britain before it became Junior 100B.

I hit another kart and rolled it, and as a direct result of my accident, the MSA introduced extended rear bumpers.

 

They in fact introduced extended rear bumpers because of the death of Spencer at Kimbolton.

 

43.4 BHP @ 21,000 RPM from 100 cc was available in 1965 I believe

 

20 thou piston clearance is way more than ive ever run m8 !!