ESE's works engine tuner

[RAW]

A little read on HIPPING

http://www.dtic.mil/dtic/tr/fulltext/u2/a105562.pdf

[F5 Dave]

Is that a bit like Dogging? Not sure I want to click on that link

[DaisyB]

Chaps, would appreciate a little help or pointers, the series I race in has fairly big problems with noise, the limit for us 2 strokes is 105db but most of us are about the 107 mark, I've tried all manner of different absorption silencers without being able to get it down much. It appears that next season the noise testers will stop being as "helpfull" as before. Any ideas on how to get the engines quieter without affecting performance? (air cooled geared engines for the most part, though the autos are as bad and are all watercooled) Thanks.

[1948rod]

Chaps, would appreciate a little help or pointers, the series I race in has fairly big problems with noise, the limit for us 2 strokes is 105db but most of us are about the 107 mark, I've tried all manner of different absorption silencers without being able to get it down much. It appears that next season the noise testers will stop being as "helpfull" as before. Any ideas on how to get the engines quieter without affecting performance? (air cooled geared engines for the most part, though the autos are as bad and are all watercooled) Thanks.

Intake noise plays a blg part of the overall noise. Karts losing an air box are black flagged for noise. A large amt. of noise comes from the thin walls of the chamber so wrapping the rear part would help and also keep the pipe warm. For a quick fix at the track try some silicone beads along the chamber and a couple of hose clamps around the chamber.

[wobbly]

An easy fix for noise is to shove the stinger up to the beginning of the rear cone.
Put the nozzle at the exit so its easy to change - then a short sleeve into a normal muffler.
This kills the high frequency racket that makes the dBA meter go spastic.

Air boxes as used by karts work great at killing noise - I built one that had 4 - 30mm intake tubes, all varying lengths.
In the 125 SKUSA CR125 engine this made around 1.5HP more ( in 40 ) than a normal pleated filter.

[jamathi]

An easy fix for noise is to shove the stinger up to the beginning of the rear cone.
Put the nozzle at the exit so its easy to change - then a short sleeve into a normal muffler.
This kills the high frequency racket that makes the dBA meter go spastic.

Air boxes as used by karts work great at killing noise - I built one that had 4 - 30mm intake tubes, all varying lengths.
In the 125 SKUSA CR125 engine this made around 1.5HP more ( in 40 ) than a normal pleated filter.

The nozzle on the end.
I tried that on the 50cc Garelli.
It worked quite well...
1983, why O why didn't I use it forever after that?

[lohring]

We did a lot of dyno testing on noise reduction for 26 cc engine powered RC race boats. We used an internal stinger as described above combined with stinger water injection from the cooling system outlet. The double can stinger muffler after the water injection made the engine quiet enough to hear water slapping the hull. I've used everything from Axe deodorant cans to energy and aluminum beer cans for the muffler shell. We got less than 80 Db measured on the shore as the boats passed. Unmuffled boats can register over 100 Db. Otherwise we always wore hearing protection during dyno testing since the engines registered 110 Db without muffling. Water injection is going to be a non starter on land vehicles, though.

Lohring Miller

[Frits Overmars]

We did a lot of dyno testing on noise reduction for 26 cc engine powered RC race boats. We used an internal stinger as described above combined with stinger water injection from the cooling system outlet. The double can stinger muffler after the water injection made the engine quiet enough to hear water slapping the hull. I've used everything from Axe deodorant cans to energy and aluminum beer cans for the muffler shell. We got less than 80 Db measured on the shore as the boats passed. Unmuffled boats can register over 100 Db. Otherwise we always wore hearing protection during dyno testing since the engines registered 110 Db without muffling. Water injection is going to be a non starter on land vehicles, though.

My knowledge of boats can accurately be described as non-existent, so this may be a dumb question:
why don't you put the stinger under water? You'd have less noise and a bit of thrust as well, wouldn't you?

[MotleyCrue]

Next time try being a bit more vague.....

....and yet several people knew exactly what I was thinking of............long tail boats. Not so easy to google when I didn't know what they were called. Thanks guys.

[guyhockley]

Radial serrations and clamped up via a bolt through the center ? How'd you cut the radial teeth ?
Historically Hirth couplings have only been used where someone was prepared to pay a big bill....

Think the original Hirth couplings had dual pitch bolt as well... Google isn't finding it so it may be the oldtimers kicking in!

Ariel decided to do a "cheapie" version of that centre coupling on their two stroke twins (ask TZ) and made theirs with a tapered shaft and woodruff key, as in ignition flywheels - It wreaked havoc with the ignition timing when it decided to move!
Don't think the Hirth arrangement would move (so long as the bolt remained tight).
Guess the "key" to machining the Hirth Coupling is as Flettner says, ie turning it to size and of course true, (after fitting up).

I had a (mechanically competent) mate who swore that his old Ariel was what we would now call Big Bang, pistons rising and falling together. He said it looked like it came from the factory like that.
There is an aftermarket 250 twin engine for Lambrettas that uses a conical join but with 4 "keys".
I was always a bit bemused by the Italian two stroke twins' crank joining method, this one's a Harley/Aermacchi but there were others with the same system, I think. Copying or all designed by the same (Dutch?)man?
There was a discussion on Michael Moore's MC-Chassis about Hirth couplings fairly recently.

[Ocean1]

I was always a bit bemused by the Italian two stroke twins' crank joining method, this one's a Harley/Aermacchi but there were others with the same system, I think. Copying or all designed by the same (Dutch?)man?

Known in most industries as a muff coupling.

Not just pre Itallian twin, it's pre motorcycle. Probably pre traction engine come to that...

[marsheng]

Put the nozzle at the exit so its easy to change

Hi Wobbly, not sure what you mean here ?

If the rear cone is curved to get around a frame, may be difficult to change the stinger options. This is if I'm getting you right.

[Grumph]

Think the original Hirth couplings had dual pitch bolt as well... Google isn't finding it so it may be the oldtimers kicking in!quote

NSU race twins of the 50's ? It rings a bell. Guzzi did an inline four around then too which I think used Hirth couplings on the crank.





I had a (mechanically competent) mate who swore that his old Ariel was what we would now call Big Bang, pistons rising and falling together. He said it looked like it came from the factory like that.quote

One of the works Suzuki TR750 riders (Aldana ?) is reputed to have downshifted so violently during Daytona practise that he turned the triple into a "tringle"




There is an aftermarket 250 twin engine for Lambrettas that uses a conical join but with 4 "keys".
I was always a bit bemused by the Italian two stroke twins' crank joining method, this one's a Harley/Aermacchi but there were others with the same system, I think. Copying or all designed by the same (Dutch?)man?
There was a discussion on Michael Moore's MC-Chassis about Hirth couplings fairly recently.

When Aermacchi copied the TR/TD Yamaha twins it was on the cheap...Yamaha uses a splined joint there...

[WilDun]

I had a (mechanically competent) mate who swore that his old Ariel was what we would now call Big Bang, pistons rising and falling together.

Talked to an old American guy from Nevada who sold Suzukis and when the first fast six speed Suzuki twins came out, (T20) they tried them in desert racing but used the arrangement you are discussing (pistons rising and falling together) and called them "Twingles".

[wobbly]

You dont change the internal stinger ( and this is easily bent to fit a curved rear cone - but does not need to be,as the gas pressure can be bled off from anywhere ).
I welded a clamp tube to the end of the rear cone, and this had slide in nozzles that determined the back pressure.
The clamp tube then had a slip on muffler after the nozzle.