NEW 45 engine

[ALLAN YUEN]

I like the 91 M1 motor
I ran a pair in a twin at Brandon this year
Out of the box the performance was quite good.

There is 91 M1 and 91 Inline. The 91 inline appears to have the M1 features

Best CMB 91 M-line red head 6 bolts than CMB RS EVO gold head four bolts? Is M-line more powerful? And use turbo plug Rossi 8T plug?

 

[AgafonovRoman]

I don't like it. But using a square drive remedies the situation (by allowing the flex shaft to "float" within the coupler, and not push up against the crankshaft, transferring the torque to the rear rotor assy)

I think when you use a cone on a flywheel and tight it with any regular nut(square ore coupler) it stops what move...

 

[David Bryant]

I think when you use a cone on a flywheel and tight it with any regular nut(square ore coupler) it stops what move...

you mean the flywheel collet itself?

 

[AgafonovRoman]

you mean the flywheel collet itself?

oh yeah I did not know the right word for it. I call it cone.

 

[dr gary turner]

I have not seen an M1 P/S for 45

My M1 21 the difference is a dish piston and turbo head button
It actually came with 2 HB , one for low nitro and one for high nitro

 

[David Bryant]

oh yeah I did not know the right word for it. I call it cone.
View attachment 284634

I see, thanks

 

[Rudi Arnesen]

I talked Tony Australia about 91 m-line it can use both collet and square. Not arrive new CMB45 M-line yet because factory workers delay from Covid-19

You cannot use rund flex on M-line engines, they are not designed for it only square drive

 

[Ian Inverarity]

Rudi, a friend uses round drive on an M line 45 and 91 with no issues. Can you explain what will go wrong with the engines using round drive?

 

[Rudi Arnesen]

If you dismantle the engine you will see why. All the energy will be on the front end bearing and to the front part of the crank

 

[Ian Inverarity]

Rudi, by front, do you mean the disc end? I have seen my friends engines dismantled.

 

[Buckshot]

After disassembling and inspecting my .91 M-Line I saw no need to use a square drive only. I’m running it with a round collet and have had no issues.

 

[Alan Elzer]

Square drive will work just fine with mouth conversion

 

[gilbert galli]

on engines which do not have a front bearing retaining circlip and if the drive dog play is too important, it is the bearing which takes the thrust of the propeller and this forces on the crankshaft, with a square drive with ferule the pushed is done on the strut

 

[Ian Inverarity]

Gilbert, a Zenoah (for example) also does not have a circlip to retain the bearing at the collet end, also does not fasten the crankshaft to the inner race of the bearing at the collet end, also has the prop thrust taken through the crankshaft and is resisted by the bearing at the opposite end from the collet. By far the majority of Zenoahs would run that way without issues. Why would this be a problem for the CMB M line engines which in fact support the crankshaft better with 2 bearings at the collet end which should prevent deflection of the crank pin and collet end of the crankshaft under load?

 

[gilbert galli]

it is possible that the bearings are mounted tighter in a zenoah crankcase, the longitudinal play of a zenoah crankshaft may be greater,
the connecting rod of a zenoah is also freer

 

[Ian Inverarity]

Gilbert;
1. No, from my experience about the same.
2. Not dissimilar, but how is that relevant anyway? If the Zenoah had excessive axial play then potentially the crank could run on the side of the conrod and I’ve never seen that issue.
3. You mean axially? Zenoah rods are tighter at the piston end of the conrod compared to CMB nitro engines.
What damage or harm do you expect to an M line engine and what would cause it?

 

[gilbert galli]

it is possible that the thrust on the crankshaft with a faster engine speed causes clamping or breakage,
it should be remembered that the imbra races last longer in the fsro or fsrv category

 

[Ian Inverarity]

Gilbert, so are you saying the crank shaft web may slip on the crank pin trapping the conrod between the two crank webs? Have you seen this with the M Line engines? How is this RPM related? We will watch out for this issue! What I can say is that I have has several RS101 crank pins break from high RPM use while only supported by two bearings and using square drive. I made my own 2 bearing housing for my RS101 Evo before CMB released the DFB and M line engines to stop the pin breakage.

 

[Joe Warren]

the M91 Piston is a mild mod on front of liner to improve fuel flow. something most were doing 10 years ago.

 

[LohringMiller]

I have no experience with the nitro CMBs, but Mike Bontoft built a new front end that added another bearing to the front of the CMB 35. This reduced crankshaft flexing that caused flywheel strikes on the magneto. We also replaced the magneto with the Quickdraw solid state ignition.

Lohring Miller