CMB 45 Rod Failure

[DaveMarles]

Tim K. When you want to case harden a particular part of a steel item, you copper plate the parts that you do not want hardening. Its a standard engineering procedure. Other steel conrods are plated for the same reason.

Dave

 

[Ian Inverarity]

If it was a material problem how come both rods broke in the same place? Unless the material used was not up to the job? The beakage is thru the thickest section of the rod!!! :huh:

Ian.

 

[Geraghty]

If I am not mistaken,you don't want a totally hardened steel rod.That just makes the rod brittle and really susceptable cracks and breakage.They only want the hardening to take place where the needles ride.Needles are harder than the hubs of hell and will tear the hell out of a non hardened surface.Look what they do to the face of the drum which is not hardened.

Think about it.It would cheaper to harden the whole rod.The rod is already spending the time in the heat treat furnace.Why go to the expense of copper plating before heat treating.There is an advantage to "not" hardening the whole rod.

This is definitely a material [or lack of] problem.But why all of a sudden now?CMB rods have been bullet-proof for as long as I can remember.

This problem smells of a new supplier of rods to CMB or a material change by CMB to save $$$$$$$ or ???????????????

What makes this so frustrating is not the cost of the rod.Big deal!!! Thats just racin'.It is the collateral damage that occurs when the rod grenades.

 

[izitbrokeyet?]

for what it's worth:

That looks like a repetitive strain failure (usually caused by crack propagation) That material is too brittle or may have had a small scratch in it that grew into what you see in the pics.

 

[Tim Kish]

Thanks for the info Dave I didnt realize the rod was only case hardened.

I think I will stick to my OPS LOL.

Probably material then.

Tim K

 

[TOM MOORE]

Wohoo!! Looks so similar to mine.. it's scary!! Methinks a trend is developing.
What to do??

Send it back to TIDEWATER. They had a run of cams that had that problem mine broke and had been modified and they still fixed it free of charge. send it back.

Tom

 

[Joe Warren]

Floppy is this a CMB Purple head CAM 45? the 1st 300 CAM45`s Had a .260 Crank Pin. Never had a problem with Most of them... THEN Someone @ CMB decides to mfg a .230 Crank Pin with the Last batch Of CAM 45`s. ALL THESE ENGINES BURNED PINS, NEEDLES & RODS. MEASURE YOUR CRANK PIN IF IT IS A .230 CRANK PIN CRANK NOW? TIDEWATER HAS A FIX FOR THAT ENGINE & IT IS THE EARILER .260 PIN CRANK & A SET OF NEEDLES.? MOST WERE REPLACED UNDER WARRANTY. THIS INFO CAME FROM THE OWNER OF TIDEWATER THE NORTH AMERICA DIST. I HAD A PROBLEM WITH THE SAME CAM45 ENGINE LAST YEAR.

 

[DaveMarles]

If it was a material problem how come both rods broke in the same place? Unless the material used was not up to the job? The beakage is thru the thickest section of the rod!!! :huh:

I don't know why the rod would break at that point but it is a stress point. The rod section at that point looks to be the thickest part of the rod but because of the way its made which is parallel on the end view and then machined to make it into an H section it actually has only the same amount of material in the cross section at that point as it has near the top of the rod and on one rod I just measured its less. Thats because the groove that makes it into an H section is wider and deeper at the bottom. Maybe thats partly to blame but it shouldnt break so send it back.

Dave

 

[Ian Inverarity]

Dave,

Aren't the flanges of the H section a constant width, so the web is wider at the bottom end of the rod? This would mean a greater cross section near the bottom (but not by much), so again it seems strange to break there? :huh: Has the machining on the rods in that area changed recently?

Ian.

 

[DaveMarles]

On the later rods the groove in the side of the rod gets wider as it gets down towards the big end but on some rods it also gets deeper making it a stress point but it still should not break. Maybe the plating wasnt done correctly and the rod is hardened making it brittle. Certainly not a user problem.

 

[craig]

My one is the latest 2004 cam from tidewater small pin grooved oil holes on rod releived drum valve for better lubrication to big end my one was running fine until i changed props went from a H18 to a H22 then bang it was on a hydro

 

[Wild Bill]

I got a new engine from Tidewater, waited for the 2004 spec. model. Broke mine exactly the same way. First day out with about 20 minutes running on it.

Got in touch with Tidewater but was not able to get any warranty. Had to buy:

1 x Case (when the rod broke, it went out the side of the case)

1 x Piston and Cylinder (the rod broke the bottom off the piston and dented the Liner)

1 x Rod

1 x set Needles

1 x pr. Bearings

Put it back together. Checked everything. Ran for about another 20 minutes and boom. Exactly he same thing. I don't know what to do now. I don't think it's worth spending more money to replace all this again and have a third shot at it.

I think I will go back to my old Evo. At least when the crank in them breaks, it only costs the crank pin and some needles.

My feeling is that CMB have a problem with these motors and I don't feel like spending more of my money to help them with their engine development.

I am close to Arthur, Bobby and Sandy at Tidewater and feel they are doing their best. I beleive this is the factories problem and that they should make public any problems and assist their customers with some form of rectification.

Sorry I can't help you guys, I am in the same boat looking for answers.

Bill Annabel.

 

[bsmtboy2]

I have the same motor ready to break in but i think we should contact CMB directly about this and get some replacement parts to remedy the problem asap. Anyone have the official website for CMB, if not maybe our Euro fellow racers can help us out with contact info or pass this thread on to them. B)

 

[Bart Drieghe]

There is no website or so of CMB , maybe u might try to get a hold of Ian folkson , he's an official distributor :

[email protected]

try to contact him , he might give u more info how to reach Mauro ( cmb ) or , u might try to contact andy , maybe he can do something too .

Regards ,

Bart

 

[bsmtboy2]

Andy, can you shed some light on this and help contact CMB on this seemingly reoccurring motor problem :huh:

 

[Don Ferrette]

Dave Marles is the best path to Maurio. B)

 

[Don Ferrette]

"I am close to Arthur, Bobby and Sandy at Tidewater and feel they are doing their best."

I can't really agree with this. When I last ran the CMB motors I purchased them from Hobby Supplies in Australia. I didn't lose an engine but did have a bad rod in one which was replaced at no charge. I have nothing against Arthur & the gang at Tidewater but they get top dollar for what they carry & need to stand behind what they sell in return for the profits they make, that's just good business. If you buy a lawnmower from Sears & the engine blows right after you bought it, you don't send it to Briggs & Stratton, you take it back to Sears. :blink:

 

[TimD]

I was at the pond when Wild Bill broke his 2004 cam. I think it is BS that he had to pay for all the replacement parts.... There was no way it was a user error!

Has anyone checked that the bore is square to the crank?

 

[Wild Bill]

No, but you can have the bits and 'go for it'. I would just like to know why and see if it can be fixed - long term.

Thanks mate.

Bill

 

[craig]

Do mac motors have the same problem they are made in the same factory ????

if it is a design problem why has mac not got the same problem