Reeds

[TDR_50]

Powerabout.
A single cylinder motor turning 10,000 rpm , the reeds would have to open and close 166.66666 times a second. In the 80's We put a lexan window in the reed cavity and did high speed photos of the reeds. At that time the cameras are not up to par with todays standards. They are on pulse mode and very slightly open and close as the crankcase preassures fluxuated. Physics are not condusive for the amount of mass(reed petal ) noy only to move that fast, but stop and change directions 332 times in 1 second.

[Raceman]

powerabout,Its pretty much common knowledge when you break a reed{same as leaving one out}you slow down...wether you'r turning 6,7,8,9,or 10k plus,no matter,I don't think anyone will argue about that.Anyone who builds ultra high perf motors I believe will tell you the first sign of a broken reed is approx a 1000 rpm loss.Really shouldn't need a dyno test to prove that,,...Reeds not opening and closing at high RPM's in my opinion is right there with the boogy man and the Flat Earth Society,Chris

I've posted this before, but before y'all were registered here, so here goes again:

I've got a friend who retired from Merc after 20+ years, partly in warranty, and partly as a service school instructor. His dad worked for Merc back in the Carl K days and ran the Sarasota prooving ground, as well as a tour at Lake X in some capacity way back when. Both of these guys said that Merc had an engine in Wisconsin for test purposes in which they started takin' reed pedals out until the engine wouldn't start, and then put just enough back in to get it fired. The purpose of the test was to PROVE that the reeds became less important as RPM increased. The story, repeated many times was that by whatever means they tested and at whatever the top RPM of the test engine was, that there was an INSIGNIFICANT DIFFERENCE in the output of the engine with a full set of reeds vs whatever it was they removed. Keep in mind that this was YEARS ago, in some old inline Merc (I think they said it was an old 4 cyl, maybe a Mark 55) but it's also worth noting that the RPM's were CONSIDERABLY lower than what the high horse V6's are being turned today under race conditions.

I didn't see the test, and I've NEVER popped a reed in one of my engines, so just passin' along the tale and opinion of two guys with back to back Merc careers spanning from the 40's until into the 90's together.

I guess I'm one of those flat earth and boogy people who DO THINK that at some RPM the reeds probably cease to cycle fully, and also think that hustling one brand of reed over another for the sake of improving top end numbers is sellin' snake oil........... boogey man theories or not.

[Mark75H]

V-6's may be more sensitive

I've raced reed valve bikes and inline Mercs ... a single broken reed is generally undetectable ... if you could get the motor started and above idle.

[Raceman]

V-6's may be more sensitive

I've raced reed valve bikes and inline Mercs ... a single broken reed is generally undetectable ... if you could get the motor started and above idle.

That's what I would think also. In any case I'd have a tough time believin' 1000 RPM loss for a single broken reed.

[ChrisCarsonMarine]

Raceman,iv'e seen the story many times in the past,and i don't personally believe it,just me.As far as the 330 times a second at 10000 rpm's to stop and change directions,that poor reed. I figure if the rod and piston can do it,the reed ought to be able to,seeing that it's a little lighter,don't you think?As far as different brands of reed performing differently,i would expect reeds of similar materials and of similar design to be similar in performance,however,not all reeds are similar in design and material,and I feel some reeds can add some performance,more than others,an opinion not just my own.Yes,physics does play a part in this,mass times velocity squared equals momentum.Hence,a lighter material[than metal]will have an easier time stopping,and changing directions quickly,requiring less energy .Wave a metal rod back and forth,compare the energy required,as compared to a wooden dowell of the same size,I think you'll get the adea.Just my thoughts...chris

[Capt.Insane-o]

That's what I would think also. In any case I'd have a tough time believin' 1000 RPM loss for a single broken reed.

Had a 175 efi this summer with 4 missing petals on various cylinders. It ran like crap and was way down on top end. A new set of TDR's picked it up 1500 rpm and 12 mph.

One of my two liters gagged on a couple petals and it was an immediate difference in performance.

Opti's are very easy to tell on top end with petals missing too.

[josh hoefert]

I've posted this before, but before y'all were registered here, so here goes again:

I've got a friend who retired from Merc after 20+ years, partly in warranty, and partly as a service school instructor. His dad worked for Merc back in the Carl K days and ran the Sarasota prooving ground, as well as a tour at Lake X in some capacity way back when. Both of these guys said that Merc had an engine in Wisconsin for test purposes in which they started takin' reed pedals out until the engine wouldn't start, and then put just enough back in to get it fired. The purpose of the test was to PROVE that the reeds became less important as RPM increased. The story, repeated many times was that by whatever means they tested and at whatever the top RPM of the test engine was, that there was an INSIGNIFICANT DIFFERENCE in the output of the engine with a full set of reeds vs whatever it was they removed. Keep in mind that this was YEARS ago, in some old inline Merc (I think they said it was an old 4 cyl, maybe a Mark 55) but it's also worth noting that the RPM's were CONSIDERABLY lower than what the high horse V6's are being turned today under race conditions.

I didn't see the test, and I've NEVER popped a reed in one of my engines, so just passin' along the tale and opinion of two guys with back to back Merc careers spanning from the 40's until into the 90's together.

I guess I'm one of those flat earth and boogy people who DO THINK that at some RPM the reeds probably cease to cycle fully, and also think that hustling one brand of reed over another for the sake of improving top end numbers is sellin' snake oil........... boogey man theories or not.

Sounds like the two old guys have been through alot of interesting test!
Just a thought, try and pull a few reeds out and see how well she runs.

[ChrisCarsonMarine]

Josh,you'r learning,proud of you

[Dave S]

My buddys boat was not running rite. I took it for a spin. I scared the bunch in it. Full throtlle turns . No problems. It would idle like crap..... had no mid range. Turns out 1/2 of the reeds were broken. Rubber cages. I think the old style cages are better. Thick oil to help the slamm.

[powerabout]

That was probably waitomo, about 1.5hrs drive from here. Yea Tauranga's a cool place - 45mins from here. We've got all the lakes tho

Sorry, back on topic... powerabout - thats interesting. Was it actually made to test reeds?

Yes with high speed photography so they could see what was happening.
The usually use Yam bike engine stuff at the uni but the reed info is the same.
I am sure I paid to download it from the SAE but I cant find it. damn...

There have been a few who do CFD studies, I will post one of them.
Cheers

[powerabout]

Here's some stuff from Fluent CFD
Personnally I think it is more complicated as the reed has a mass and a natural frequency and the speed of opening changes with revs and the flow through it is not constant with the revs ( VE, torque curve) etc etc

Not to mention the reed block ange at rest as most engines use just one angle and some use 2 ( on v block reeds that is) I guess for wider torque band?

With so many variables and no absolutes I'm sure this will be a topic to talked about for years ( as it has been)and clearly there is no one reed for every job.

I'm sure even with air density changes you could probaby optimise the reed thickness/material just for that day as you would other tuning variables in the engine.

[powerabout]

Powerabout.
A single cylinder motor turning 10,000 rpm , the reeds would have to open and close 166.66666 times a second. In the 80's We put a lexan window in the reed cavity and did high speed photos of the reeds. At that time the cameras are not up to par with todays standards. They are on pulse mode and very slightly open and close as the crankcase preassures fluxuated. Physics are not condusive for the amount of mass(reed petal ) noy only to move that fast, but stop and change directions 332 times in 1 second.

Is it time to do the test again with some newer tools?
I would have thought you could do it with an advancing timing light shining down the hole and see if when turning the knob you can get a strobe of it closed or not ?
Cheers

[jody504]

Do the reed close at high Rpm I would think that if they didn't.and you belive they don't .Please take them out give us the results.But just for thauth.Do they open.I got alot of people they say they couldn't have low compression the motor was running to good.Do I take the ring out they run on top end with low compression.If you can get it to fire up It wouldn't need them ring now would it it would make compression.which reed are better all the Reed guys seam to have the ansewed that in this thread.If his Reeds are best on top end they ant wourth a **** on the bottom seam like.And the stick thory If you change from steel to would that would depend on what kind of wood you use I always would pick the wood that would not brake when I was a kid so maybe some wooden reeds would work.Does anybody make thomson gas proof for the wood.So I would think that nobody can build the best all around reed cause intell they know what you are doing with the engine and coustum build it for that Rpm,compresion rato,intake setup,and whatever else you have done to your engine they are blowing smoke.So who ever sell the most reed from all these post may Have just Made the change like the other Lieir named Obama.

[bigbore]

Flexability n longevity is key,when they open (all the way)to let the motor hit the power-band,n there manitory (pretty much) for idle,2 prevent gas n oil from spu=in out the front.

[scc82]

Do the reed close at high Rpm I would think that if they didn't.and you belive they don't .Please take them out give us the results.But just for thauth.Do they open.I got alot of people they say they couldn't have low compression the motor was running to good.Do I take the ring out they run on top end with low compression.If you can get it to fire up It wouldn't need them ring now would it it would make compression.which reed are better all the Reed guys seam to have the ansewed that in this thread.If his Reeds are best on top end they ant wourth a **** on the bottom seam like.And the stick thory If you change from steel to would that would depend on what kind of wood you use I always would pick the wood that would not brake when I was a kid so maybe some wooden reeds would work.Does anybody make thomson gas proof for the wood.So I would think that nobody can build the best all around reed cause intell they know what you are doing with the engine and coustum build it for that Rpm,compresion rato,intake setup,and whatever else you have done to your engine they are blowing smoke.So who ever sell the most reed from all these post may Have just Made the change like the other Lieir named Obama.