Zimmerman Disk intake .21

[dwilfong]

Just throwing this at the wall to see what you all think.

I have bin thinking of making a disk intake for a CMB .21 eng.

Would it be worth the effort?

Have a design in my head and have made a few sketches on paper.

It looks like it can be done with the case designs of the VAC and earlier .21 eng.

The biggest pain would be making the disk.

I know that some have made disks before.

Need some info on how to make a disk or have one made.

 

[Chris Wood]

i have said it a thousand times.. you put a zimmerman disc in a 21 motor and get rid of the drum.. WHOLE NEW ANIMAL.. and i THINK ( WALLSTER HELP ) yrs and yrs ago cmb ( i am talking along time ago ) CMB used to make a zimmerman disc 21motor.. i think the crank pin was in the center of the crank..

either way .. good luck and keep me posted.. there is something there i think

i thought rod g yrs ago was having some made out of carbon fiber???

chris

 

[Leon Morgan]

Carbon fibre is used a lot. Some pictures from Ronny Riedel's CMB 91RS

 

[dwilfong]

Now that looks good.

Maybe use CF sheets and cut the disk from that?

the intake will not be to hard to make. Can use the PTO like the outboard has to drive the disk.

will make it from scratch but you get the idea.

Put the carb on a down slant like the old CMB eng's

then make the carb oval boar to fill the window like I have on my 1.01

will be light and easy to spin up.

the carb and disk window can be a good size not restricted like a crank choker or a drum.

 

[bermudadude]

disk was always better ,everyone started switching to drums because as the horsepower and rpms started rising with better piston/liner materials, they started destroying disks. been sayin for a while that cmb should bring back the 67/80 disk engines...very light and i.m.o better performing.

i believe the carbon disk thing is a tricky area. its like chroming the alu liners ,only 1 company got it right (i think moki for the liners) i t cant remember but i think it was picco(???) the carbon disk will shatter more often than a steel 1 but when it goes it wont destroy the engine,but picco had a special epoxy for the disk that wasnt degraded by nitro. i may not be right about it being picco

or somebody could commission dow chemicals to make the epoxy then get a company to make the carbon laminate,experimenting to get just the right weave/grade/thinkness/stiffness combo for our style engines......any trust fund babies in here? lol

 

[dwilfong]

disk was always better ,everyone started switching to drums because as the horsepower and rpms started rising with better piston/liner materials, they started destroying disks. been sayin for a while that cmb should bring back the 67/80 disk engines...very light and i.m.o better performing.

i believe the carbon disk thing is a tricky area. its like chroming the alu liners ,only 1 company got it right (i think moki for the liners) i t cant remember but i think it was picco(???) the carbon disk will shatter more often than a steel 1 but when it goes it wont destroy the engine,but picco had a special epoxy for the disk that wasnt degraded by nitro. i may not be right about it being picco

or somebody could commission dow chemicals to make the epoxy then get a company to make the carbon laminate,experimenting to get just the right weave/grade/thinkness/stiffness combo for our style engines......any trust fund babies in here? lol

I have a few of the .67/.80 disk eng I run and I do love them. the one I run now is a .67 crank and a .80 P/L making a .77

I have seen some uses spring steel and make the disk from that. but then the expense of getting it laser cut.

 

[RaceMechaniX]

I think we have all seen the Novarossi tether car motors with disc's. Very nice examples attached from the tether car world.

 

[brad nichols]

Any pics of the inside of the Nova? Great looking set-up!! Drums don't need to be set -up like the disc engines did. Rotors and back plates needed to be lapped and disc clearence needed to be set to keep engine running in top shape. Too much maintenance for the sport boater As Shawn stated, the epoxy and carbon would need to be formulated to stand up to the nitro without turning soft or swelling.

Brad

 

[Anders_Martinelle]

It was Picco that had CF disc on their large case 90 in the later part of the 80:th.
Nothing to spend time on........
Small pieces came off the disk and killed the P/L quite Quick.

I run the Picco 29 today in my tethercar together with OPS 29 in my old car both with Zimmerman intakes.
We have discussed it alot why it`s so common in tethercar racing and the only reson i can come up with is that when you race at top speed you have around 70-85G load sideways and that make the drum "Heavy" and increased friction.
A friend of my have tested with PEEK drum and that works good also.
In tests behind the garage i have not seen any difference between drum or Zimmerman disc when it come to RPM differences.

Anders

 

[Ken Webb]

What advantage does the Zimmerman valve have over disk and barrel valves?

 

[dwilfong]

You can put the carb real close to the valve. This way the mix will expand quick in to the case.

With a drum it is in a long tube for a time and can puddle up and come out of suspension.

Now sucking thew the crank and having the rod do the work helps.

But what do you lose in flow going thew the gauntlet?

Also the way I port my engs there is a direct shot to the port transition at the liner.

A less windy road to the cylinder for the mix to come out of suspension.

Every time you go around a corner it will create high and low pressure spots.

The same thing that makes rain in the atmosphere.

Change the atmosphere at different point in the case and you get fuel droplets forming in the low pressure zones.

I don't think just popping a disk on the eng will do much. But what it will allow for in the long run I think will.

I have had very good results with this porting scenario with my RS 1.01,.45 and EVO.77 Just wonder if it would pan out in a .21

 

[Tom Foley]

The VAC 91 drum intake works great once you loosen the fit up some.

 

[wayne middlemiss]

laser cut shim steel I feel would be the only way been use in many gp engines kart engines dap parrila etc. also worth looking at the way the etch the reed petals in pulse jet engines. and like others have said already re picco comp 90 carbonfiber disc's don't even look at it you would be lucky to get a launch on them.

 

[lohring]

Disks are easier to make, but a bell valve will have more time/area in the same diameter.

Lohring Miller

 

[Chris Wood]

a 21 has NO TORQUE.. a drum dragging around in oil is DRAG.. huge torque loss.. not as fast of response to fuel changes also ( in my own opinion ) big motors you don't notice it much as they have torque.. little motors.. not so much.

 

[Tim Kish]

Send Frank Orlic an email David.

He was playing with this about ten years ago ?

Tim

 

[Anders_Martinelle]

Chris, a big disk dragging in oil is that better????

Anders

 

[dwilfong]

I don't know if the drag would be less but the weight to spin up would be less.

The main reason I see a advantage as I said is the flow difference.

As for the timed area. when you make a wide window it changes the time area. The window needs to be wide not round.

I have found this out with mt RS 1.01 real quick.

A stock disk in a wide window changes the timing allot!!!!!

the window stayed open much longer at full hight. say you have a .500 boar carb. Now make it .300 wider the .500 cross section is open much longer with the same disk.

More timed area in the same amount of crank timing.

Kinda stumbled on this with out even giving it a thought.

 

[bermudadude]

the original gold head evo cmb is the real horse. that had a nice wide window.the reason i refuse to buy 1 of the new ones. that and all i hear(and see) is people changing bearings and "fixing" the new cmbs, a classic case of THEY DONT MAKE EM LIKE THEY USED TO.

another thing is ,thru much experiment ,after being tipped off by art mcmeans (tidewater-back in the day) u can reduce oil content with the disk engines and with hi nitro u get better performance,nitro doesnt like oil(over simplified yes)

i notice the drum engines need more oil to keep em from destroying themselves but the oil is drag with all the contact on moving surfaces. where as the disk simply cuts thru the film ,probably just an air pocket or vaccum at high rpm

10% or less oil with disk

vs

15%-20% with drum

 

[Chris Wood]

Chris, a big disk dragging in oil is that better????

Anders

Hi anders

i say yes.. while a disc in oil is alot.. it has no where near the overall physical size a drum does. more rotational mass. If you look at all the evo motors the one thing they have in common is they have good TORQUE.. the down fall to them was the 2 pc crank system. I personally would like to see a vac type motor with a disc. i think it would make the motor a whole new dynamic.

but that is just my own opinion.. until it gets made we will never know.