OLD_SLOW and in the WAY

the units i tested have a 355ml volume ( as reference it the same volume as a 12oz pop can) with a 3/8" diameter intake horn by 1" long, the horn can be anywhere on the resonator. basically it uses the spitback to help charge the resonator box and the inertia of the incoming air through the smaller opening overcomes the spitback which supercharges the next intake cycle. the engine comes on like a nitrous shot. the shape of the resonator isnt critical as long as you have 1" between the carb opening and the resonator wall, you will have to have the intake runner lenght set at 3 13/16" from piston face to carb opening. the resonator will give you some insurance in a dunking by keeping from gettin hydro'd.
nevermind the aluminum chips it was in the construction stage



here are the only pice i have left of the "ratflask" hemmholz resonator.
the container was made by rubbermaid and had a very tight seal with the lid.





this is the velocity stack used inside the flask




inlet horn and grommet




interior of flask




profile of intake stack, the 5 to 8% refernces the gain over a straight carb opening



__________________________________________________ _________________

first pic is the inlet horn starts as 7/16" brass tube but after it gets flared the diameter shrinks to just a tad smaller.



the following pics are different flasks i tried



this flask was made from the stock zenoah air filter housing although sealing it was quite a challenge



this last one worked out very well it was halon fire extinguisher bottle, volume rt at 355ml



the easiest way to shape a custom flask is to buy a cheap candle just slightly larger than a pop can, melt this wax in the container, when it gets cooler and mushy then you can hand form it to the desired shape.






i am no longer in the biz so youz guyz are on your own if you want one

Ron Olson

My Feedback: (1)

Larry, I've always liked this article and glad to see that you brought it back as it's one of those cheap horsepower things that anyone can do.
If I remember correctly, this works better on stock engines with cannisters than modded ones with pipes.
What did you use for a velocity stack?

OLD_SLOW and in the WAY

this resonator is only tuned for can mufflers or straight pipes ....
i had an idea one time to synchronize the resonator and see where it peaked then disable the flask and enable the tuned pipe so you could get a double punch of power


the stack is in the second photo that mushroom lookin aluminum thing or yoy can use the original black spit tube inside the flask. the numbers i gave out were for an engine timed at 180 exh 155 intake

here is the calculator i used. just plug in your numbers as far as volume goes and in the resonance tab is where you want the RPM band to work so plug in between 13,000 to 16,000

http://www.lautsprechershop.de/tools...lmholtz_en.htm

here is a good laymans graphics of its workings

http://www.phys.unsw.edu.au/jw/Helmholtz.html

and another easier calculator

http://www.vk2zay.net/calculators/helmholtz.php

Bumpinyota

Helmoltz resonators are heavily used in car audio in the form of vented boxes - something Ive been doing for decades and something does not add up.

You said you had a volume of 355cc's for the conatiner, then a port length of 1", and a port diameter of 0.375" (0.11 sq inches of port). This does NOT yield a 13,000 to 16,000hz tunig but rather a 136hz tuning. Please advise.

Nosedragger

13,000 to 16,000 RPM not hz

16,000 rpm divided by 2 because the intake port is only open approx half of a revolution. So 8000 divided by 60 (60 seconds in a minute) = 133.33 hz

I recall other threads on this and OLD...SLOW AND IN THE WAY picked up 1500 rpm using this box, so he apparently got it right.

Bumpinyota

[homer simpson voice]
DOH!!!
[/homer simpson voice]


I forgot about the units....LOL!!

Now how well would this system work with a crankcase mounted carb engine, reed valve, etc?

You wouldn't happen tohave any links handy of those other threads would you?

Nosedragger

The other threads should be here somewhere,I did a search and didn't find anything.Maybe I saw it on another board.

siberianhusky

they used to sell "speed bottles" for Yamaha RD350's. Haven't seen one in years, not sure how they worked but they connected between the carb balance tubes on the 2 cylinder bike engine. They are a reed valve engine. Never tried one so I don't know if they work in that application.
Used to raise the exhaust port 1mm, match the base gasket, knife edge the transfers and lap the head to the cylinders and run without the head gasket. Throw on a set of Toomey pipes and go smoke any other bike on the street! I still have an 81 liquid cooled in the garage, my favorite street bike ever! In 83 they added the YPVS power valve and the bikes lost that real kick in the butt when it came on the pipe. The 81/82's would double in power at about 7-7500, it was instant, one second you were kinda putting along then all **** would break loose! It would hoist the front wheel in 3rd gear and take off!
Not beginner friendly! But sooooo much fun!
Really cool to see this idea back again, I'll be keeping an eye on this! Way too cool!
http://www.economycycle.com/servlet/...r-RD350/Detail
Yamaha has a system called YEIS (yamaha energy induction system) you might be ably to find some info there.

found the following in this thread.
http://www.rzrd500.com/phpBB2/viewto...c63548ecb249ed

f=(a/2pi) x [{pi(Dp/2)^2}/Vb{Lp+1.57(Dp/2)}]^0,5
(Helmholtz's Resonant Frequency Formula)

f= resonant frequency of bottle (ie. effective RPM)
a=speed of sound at your altitude (340m/s at sea level)
Dp=Diameter of connecting pipe in cm
Lp=Length of connecting pipe in cm
Vb=bottle volume in cc

The bottle should be at least as big as the displacement of the cylinder and the hose cross section should be at least as big as the throttle opening at the intended RPM. Yamaha's SAE paper was #810923, most technical university libraries have these on file. Keep in mind that this is to design a bottle for a single cylinder engine. I think when you connect two cylinders to the same bottle it halves the effective RPM, that is the only way the Banshee style ones could work at anywhere near the right RPM. If anyone has one of those I'd be curious to know the actual dimensions to check that theory. Bimotion also has a boost bottle calculator in it and all it does is use this formula to give you the RPM

Nosedragger

Tuned Airbox is not a boost bottle.

siberianhusky

Same idea, same principle, same math! just a different way of "storing the charge" at a certain frequency. You should have realized that from the formula I posted, It is the same formula that was used in the two web pages linked to. A resonator is a resonator, name and location don't change what it does. The math says so!
The dyno charts are very interesting, definate increases in horsepower at certain rpms, and a drop in others where you are working against the resonant frequency of the bottle or box.

Nosedragger

the real difference between the two is the tuned airbox works on rc boat engines where the boost bottles do not