Zimmerman Valves for a 21 motor

[shoboat]

Boaters,

Looking into what it takes to make a Zimmerman valve for a 21 Hydro.

I understand they are very good in tether cars, why not boats?

I thought I remember way back when one of the CMB Valvola 21's had

a Zimmerman valve induction. Would they be hard to make for a 21 motor?

Anyone make or have the knowledge to make one to test? Thanks For Any

Help On The Subject. I hear that some Swedish tether guys run

them in their cars. Believe it or not I understand that disc

and drum valves flutter around 25,000 RPM to 26,000 RPM. This

can't be good for maximum RPM. :unsure:

Curious,

Mark Sholund

231.590.3023

Email is: [email protected]

 

[dwilfong]

Mark

Funny I have bin thinking the same thing the last couple of months. Can't get the thought out of my mind :blink:

Would be nice if there was a .21 like the 45RS. Would add some weight but I bet it would more than make up for it in the long run. Would be shorter also.

David

 

[Richard Dahlheimer]

Mark

Funny I have bin thinking the same thing the last couple of months. Can't get the thought out of my mind :blink:

Would be nice if there was a .21 like the 45RS. Would add some weight but I bet it would more than make up for it in the long run. Would be shorter also.

David

I think the MAC and CMB Valvola would be the easiest to convert because they already have a extended crank pin. Instead of driving the drum valve, you would be driving the disc drive. I would have the disc drive supported by one ball bearing that was mounted in the back plate. Back plate and carb plate could be made from billet aluminum. Disc and driver would probably be the hardest to make. Richard D

 

[Chris Wood]

mark

i have been TRYING AND TRYING AND TRYING to get the same thing.. i am 100% confident the valvola would be a whole different motor with that.

i thought yrs ago the OLD cmb motors before the evo's i forget the name i swear i thought that they had a 21 yrs ago with that set up.

the only issue i see is with a single pc crank is how to connect the disc to the crank..

if you find anything let me know please

chris

 

[Wally Marsh]

My older CMB .84 Grand Prix is a one piece crank with Zimmerman valve induction system with the disk supported by ball bearings in the back plate like Richard describes. I remember it being very responsive to throttle input compared to drum induction motors. It's got to have less drag than the drum; that's got to help the little .21's.

Similar to the Evos without the headaches of two piece crankshaft.

 

Wallster

 

[Martin Hamilton]

As far as im aware CMB never made a .21 with Zimmerman induction, The very early ones from the 80s had a drum valve. 99% 0f tether cars use Zimmerman induction. Go to www.smru.se then click on technology on the left of the page and then scroll down to motors, click on the NB5 motor and theirs full pictures of Nils Bjorks 5cc Zimmerman car motor. All of the tether car motors are to this Zimmerman design. Martin.

 

[Martin Hamilton]

mark

i have been TRYING AND TRYING AND TRYING to get the same thing.. i am 100% confident the valvola would be a whole different motor with that.

i thought yrs ago the OLD cmb motors before the evo's i forget the name i swear i thought that they had a 21 yrs ago with that set up.

the only issue i see is with a single pc crank is how to connect the disc to the crank..

if you find anything let me know please

chris

 

[Martin Hamilton]

Chris the drive from the pin works the same way as in a disk or drum, The pin dives a disc as in a drum valve. But instead of say a 13 or 14mm shaft part of the drum its only 4or5mm and solid and generally runs in 2 ballraces, This is also a floating drive shaft.The back plate assembly/ rear housing is a 2 piece, The first piece that holds the drive shaft ballraces and has the induction passage in goes in the case first (This fits in just like front induction motor rear cover) but solid with 2 ballraces and drive disc/ shaft, The disc end of drive shaft has 2 flats on for valve to slide on with the valve sitting in a resesd shallow chamber,The valve is also floating. The rear cover plate that houses the carb/venturi which has a flat surface for the valve to seal against then goes on and the 4 case screws hold the 2 assemblys in the case. Like i said go to www.smru.se its easier in pictures than words. Martin

 

[Richard Dahlheimer]

Chris the drive from the pin works the same way as in a disk or drum, The pin dives a disc as in a drum valve. But instead of say a 13 or 14mm shaft part of the drum its only 4or5mm and solid and generally runs in 2 ballraces, This is also a floating drive shaft.The back plate assembly/ rear housing is a 2 piece, The first piece that holds the drive shaft ballraces and has the induction passage in goes in the case first (This fits in just like front induction motor rear cover) but solid with 2 ballraces and drive disc/ shaft, The disc end of drive shaft has 2 flats on for valve to slide on with the valve sitting in a resesd shallow chamber,The valve is also floating. The rear cover plate that houses the carb/venturi which has a flat surface for the valve to seal against then goes on and the 4 case screws hold the 2 assemblys in the case. Like i said go to www.smru.se its easier in pictures than words. Martin

One problem with the early CMB conventional disc motors was the two very small ball bearings that were used to support the disc. I came up with an idea that completly eliminated the small bearing failure. Bored the backplate to accept one larger ball bearing. physical size of the .21 back plate, would be the limiting factor for bearing size you could use. Richard D

 

[NITROSNIFER]

I like this idea.

 

[Wally Marsh]

Yes siree, (sick) minds think alike, LOL. I was just at the same Swedish tether car website, saw the same thing, a NR with Zimmerman induction. Ya just gotta know or be a good machinist with lots of time (or long building seasons like Sweden).

Thanks for posting the picture. Wallster

 

[dwilfong]

If we could just get some one to make a bolt on kit for the MAC-CMB eng.

There has to a good machinist out there that can do it. I bet they would sell like hot cakes. There are a lot of eng that could be retro fitted.

You could do it with 4 pieces,back plate with bearing ,PTO drive,disk and carb flange.

HINT,HINT

David

 

[Martin Hamilton]

That marine motor is one done by the Swedes, Also the motor of choice for tether cars in 3.5cc and 5cc is Novarossi with Zimmerman induction. The 5cc is a Novarossi .28- 4.66cc with an increased stroke to take it to just under 5cc + Zimmerman. They dont seem to get to many problems with the ballraces on the drive shaft 4mm x9mm, I know that some of the very early Zimmerman motors from 30-40 years ago did suffer problems because the drive shaft ran in a single roller bearing with the hardened drive shaft directly in the rollers. Its also these Novas that hold the world records in 3.5cc and 5cc tether cars. Not even Picco him self is as quick with his own 5cc motors. Martin.

 

[Wally Marsh]

"Its also these Novas that hold the world records in 3.5cc and 5cc tether cars."

Is there a pattern here? NR also holds current records for the boat classes they represent. The boating community just has to find a way to get Cesare Rossi and company to build them (and outboards

) to our needs and keep them happy at the same time

May the force be with us!

 

Wallster

 

[HendricX]

Disks are not a great problem.

I do CMB 65/85 RH-rotation for twin engines , as Mauro did not want to sell 'timing-uncut' disks.

It took 0,6mm/0,023" springsteel sheet , a laser/water jet for the off-set-rectangle opening.

They are oversized , so after cutting (diamond-cutttingwheel/Dremel) the inlet-timing ,

they must be made (nearly)to size by grinding. After that , I send them in for hardening .

Some minor re-grinding for exact fit and roundness and diamond file for the "pin"fit is the last step.

Becoming older has the disadvantage that your buddy's that can do those things for you , are retireing too

 

[Glenn Quarles]

"Its also these Novas that hold the world records in 3.5cc and 5cc tether cars."

Is there a pattern here? NR also holds current records for the boat classes they represent. The boating community just has to find a way to get Cesare Rossi and company to build them (and outboards

) to our needs and keep them happy at the same time

May the force be with us!

 

Wallster

Wally, Nova has been great (done almost everything I have asked) at trying to meet our needs (and the prices haven't been lower in years). What specificaly would you like to see?

Glenn

 

[John Knight]

Glenn,

How about a production NR 21 OB engine? Without having to go through the expensive conversion from an IB, if you can get them. NR would corner the market on OB's for 21 modified engines. Powerheads would be fine, we already have the Lawless, a great lower unit. Use the 5 port engine as the base engine and modify it and they will sell them.

John

 

[Chris Wood]

glenn.

i know wally is speaking about the sleeves that we are discussing.. and the outboard.

the outboard shouldn't be that hard.. move the window 180degree's from the existing crank and make a pto.. or for that matter if you could just get them to do the reverse crank and find someone to make ptos.. my father could do the pto's for you if you could just get them to do the crank.

chris

 

[Glenn Quarles]

Friends, discussions with Nova about an OB are ongoing. I have no idea if it will happen, but the discussion has been started.

And yes as Chris mentioned, Nova is building us the big exhaust port sleeves again and I should have the first few engines and P/S set here in my next order.

Stand by for more news from either Aaron or myself on the OB. If/when they are built I will have a bunch on order!

Glenn

 

[aaron alberico]

Guy's

Novarossi have been great to myself and Glen, we are working with them on new things,

change's etc...

it all just takes alittle time.

regards Aaron