Engine Failure

[dwilfong]

Les

All large CMB RS eng use full complement needle bearings on the rods. I have not had any problems with them at RPM up to 28000.

The first eng I had a .91RS did spit some needles. I am sure it was from the gross imbalance of the rotating assembly. But since then with the assembly balanced in my eng. no problems with the full complement.

So how dose a full complement work in one eng at high RPM and not the other?

So full complement dose not work?

Some one forgot to tell the CMB RS engs that............................

 

[lohring]

I'm with Les. I know full complement ceramic ball bearings work. I'm not so sure about needles, even ceramic ones. Even steel needles work with two in a slot, so rubbing isn't the problem. I'm waiting for someone to test a full complement bearing in a gas engine. My only rod failure in a gas engine was in an M&D cast cylinder engine that got run over 20,000 rpm for several race seasons. It was a cage failure that let the needles skew, destroying the rod. You can see what happened from the pictures.

Lohring Miller

 

[dwilfong]

All I am saying is if you don't try it you will never know..............................................

How hard is it to order the right size steel needles and put them in the crank??????????????????????

What a hour of your time????????????????????

Seams that the means to a end is in its favor.

LATER.........................................

David

 

[Les Smith]

Les

All large CMB RS eng use full complement needle bearings on the rods. I have not had any problems with them at RPM up to 28000.

The first eng I had a .91RS did spit some needles. I am sure it was from the gross imbalance of the rotating assembly. But since then with the assembly balanced in my eng. no problems with the full complement.

So how dose a full complement work in one eng at high RPM and not the other?

So full complement dose not work?

Some one forgot to tell the CMB RS engs that............................

David.......You need to get your facts straight! (they do not work on a crank pin for high rpms ....drive shaft u-joints on cars ok)

Your first CMB engine .91RS must of been a prototype if it had a full compliment needle assembly on the crank pin and that is why it failed...unless the cage disintegrated and went out the exhaust and when you took it apart all you saw was needles and thought it was a full compliment needle assembly.

The CMB crank pin needle assembly's retainer has a 'T' slot at each area at the end of the needles and the retainer is made out of a bronze material and as well they have reliability issues above 19K rpms.

Center photo is CMB 35RS Crank Pin Bearing

These CMB engines do not use full compliment needle bearings on the crank pin..they use a caged needle roller assembly with a bushed upper end.

 

[dwilfong]

Les

I have my facts strait.......................

NO CMB "NITRO" eng has a caged bearing.........................................including the .91 and 1.01RS.

I own ,run and disassembled the cranks on .45RS 67EVO 80EVO .91RS 1.01RS .91VAC .45VAC and thy all run full complement needles...........at very HIGH RPM's

Obviously you have no idea what "you" are talking about when it comes to Nitro eng. witch almost all .45 and larger run full complement needle bearing. Millions of nitro eng for many many years have run this.

Only the 27 and 35 gas eng run cages.

So be for you try and make me look stupid. May be you need to do your home work..........................................Or even better try and run one.................................

Mater of fact the K .91 eng had caged needles. But from what I hear thy had to be removed and replaced with full complement to keep it alive.

I am done here..............

Carry on.......................

Remember knowledge is not understanding.

 

[Les Smith]

David- You stated that all Large CMB RS engines use full compliment needle bearings on the rods...you left out some information and facts that you are talking about a nitro engine (16cc max) which are the smallest of all the CMB Engines that are large in the RS series and the Large RS series are all gasoline engines!

Les

All large CMB RS eng use full complement needle bearings on the rods. I have not had any problems with them at RPM up to 28000.

The first eng I had a .91RS did spit some needles. I am sure it was from the gross imbalance of the rotating assembly. But since then with the assembly balanced in my eng. no problems with the full complement.

So how dose a full complement work in one eng at high RPM and not the other?

So full complement dose not work?

Some one forgot to tell the CMB RS engs that............................

A 101RS is a small displacement engine (16cc) compared to a 26-34cc engine and just because it works in a small nitro engine a full compliment needle assembly will not work in a LARGE gas engine due to the rotating mass involved.

 

[dwilfong]

You know if you would read what I post before you make accusations you my look better in the end.

I clearly stated 1.01 and .91, 1.01 being stated as 16.6cc

By the way the 1.01 will pull a ABC 2818 to 24000RPM. SO how much torque you think it has.

The pigeon cheese game has rub of on you I see.

Like I said Les put down the books and try it you may like it................................................

 

[Les Smith]

Yeah your right! your pigeon cheese game at it again we all were talking about con rod pin bearing assemblies, then you come here and you wanted to talk about main crank bearings that are a full compliment which you did not design, however made from another bearing and Greg Settles did the assembly on this type of bearing and now you want someone to make a full compliment needle bearing for a gas engine to satisfy your curiosity that will only take an hour for someone to do per your standards.....only responding to what one has post and apparently you think an engine is an engine and what works for one will work for others...well maybe one has to try it before they say it won't work.....

Lets' see your 24/7 induction engine run off the bench and in a boat and be functionally better in operation compared to any other induction.....I know you are capable of launching your boat and you don't know until you try it and it will not take much time at all maybe an hour....

.

 

[dwilfong]

As always it turns in to a slam session.

I will end it here before it goes any further.

Happy boating

David.

 

[Danny King]

For what it's worth CMB RS style nitro engines have run full needles in the bottom of the rods for many many years. Despite what you think you know based on some online schematics. You are dead wrong.

They are definitely full needle setups.

They would handle the rpm and torque of a gas motor. It is a lubrication issue. Gas engines are running about 1/2 the oil a nitro motor is. But it's still worth a try. And it is almost ready to try. We will see.

 

[GRAHAME HAINES]

Hey you guys all this stuff going on since my last post has done nothing to helping me solve my problem.

This thread is not about nitro engines I am racing a Gasser now and that is what I and no doubt others are interested in knowing about.

I will say this though. Back in NZ I have and ran 2 CMB 67's in my 1/8 scales. A twin plug gold head and a later model green head.

BOTH had full compliment needle roller bearing set up's on the big end of the con rod. (11 needles from memory) when purchased

And both engines, after 20-30 minutes run time had started to wear a ring groove in the rear drum from the needles being able to float back and forth.

This wear concerned me so I switched to caged bearings. (8 rollers I think) No more wear on the drum was evident and no failure before they went into storage before moving to West Australia.

And I pulled the back end off those motors after every days running to inspect the rod and bearing. ( coz it is easy to do with a nitro motor)

So back to Tiger King and Zenoah cranks.

Lohrings photos of his brg failure is not pretty and I suspect my TK one could look like that when Gizmo split the crank.

Maybe a full compliment bearing will work but as Lohring mentioned in post 17 some hardened washers/spacers would be needed to contain and stop end float to stop potential wear on the crank webs (similar to what happened to my 67 drums)

The way I see it we need someone with the nouse and ability to set one of these cranks up this way and try it.

Danny above hit the nail on the head

Nitros run more oil than gas. so if we run full compliment then more oil maybe in order.

After all oil is not only a lubricant but also a coolant as well so if full compliment runs warmer as Les mentioned in post #20 then we may have to up the oil content.

So David Tell me how much oil are you running in your nitros.?

Lohring how much oil are you running in your gas engines and in particular what were you running when your M&D pooped?

Les Has already suggested 16oz to the US gallon which equates to 8:1

My Nitro's for what its worth ran 4:1 for the first hour of run in then I raced with 5:1 on bushed rods

My CMB's on needles ran 5:1 on run in then I raced on 6:1

As posted above 16;1 is what I have been running in my gas engines Castrol Racing A747. I am beginning to think I have not been running enough

Has any one else used this oil?

How does Klotz Techniplate go in these engines. I liked that oil back in NZ as it still has some castor in it as does the Castrol A747. Takes more heat than synthetic.

Lets get some feed back please

Grahame.

 

[LarryBeals]

Some thing left out what is the Polish grade on crank pin

Assembly when new Is the pin hardiness specs for racing engine

Or lower Rpm .Nitro fuel 18 to 20 you pick your oil Four years

Vac 91 twin hydro no crank or bearing damage oil is cheap.

This pin type is not new Ops 60 speed and 67 used this bearing

set up

 

[Tom Foley]

Let's say the Holy Grail crank gets developed , it will cost 2/3 what the engine costs then everyone will ***** about the price .

 

[lohring]

We normally run 8 oz per US gallon. We've tested higher, and power starts to decrease at much over 10 oz per gallon. We did do some gasoline engine testing with standard nitro boat fuels that had 20% oil. The main effect of more oil is a better piston seal that gives more power. Others have worked on different types and amounts of oil for the big end bearing, but I've only had one big end failure in a gas engine. Big end failures are much more common in nitro engines. Ball and needle bearings are rated in loading versus life. We usually don't put much time on our engines. My M&D engine that failed was one of my favorite engines. Most gas engines never see more than a few hours at full throttle. Misaligned crankshafts will hasten bearing failures, but I feel it's mostly a time at high rpm issue. We ran all our SAW engines between 20,000 and 25,000 maximum rpm, both on the dyno and in the boats without any rod bearing failures. Heat race engines can get a lot more time on them.

Lohring Miller

 

[Pumpin]

I have had a few 1mm stroker cranks in my 30cc zenoahs blue the bearings, I have found that when you push against the crank ie don't use a square drive this problem seems to increase so I think loading the crank can cause this problem as well the motors were being used in a road runner rigger at over 20,000 rpm for a sustained amount of time. I used 50mls of oil per litre but have also gone to 65 mls per litre but still have had the same problem. Same size zenoah in a sports hydro using a square drive ie ( not ) pushing against the crank and I got 3 years running with no big end problems at over 20,000 rpm but had little end problems ie the hardened steel washers wore out and dropped into the motor. So pushing against the crank seems to be a problem this may mean that their is a clearance problem when pushing against the crank. What are your thoughts on this lohring.

Kevin.

 

[Derret]

Reading with interest this discussion, I will add a bit of info/my thinking-

I am no expert & make no claims to be:

I think I know a bit about con rods both bushed & roller types from my years of making all types of these parts for nitro & petrol motors-

Grahame you know my thoughts here from our weekly chats via Skype-

My thinking on this goes as follows:

First: at the rpms these motors are being pushed to, motor balance scheme is critical (VERY)- rework of parts involved to be light & strong enough will help lighten loads on bottom of the rod/bearings- parts life is short if overstressed by imbalance-

Two: oil content & type/blend/oil percentage in the fuel used is of prime concern for decent rod bearing life-

Using a collet drive cable system is not good for motor/rod life-

These first two areas are fairly easy (?) to work on....

Now the hard part-

Three: these motors need pressure oil feed to the rod bottom end- not a lot but more then gets there in the present scheme/setup-

Four: The present rod/roller will be better I think if narrower/shorter) rollers are used- long un caged/crowded are limited to XX rpms if they don't stay parallel to the crank pin axis; to limit roller angling means very tight tolerances for correct assembled running specs.

This also means not enough space for right amount of oil for good lubrication-

Caged bearings work well, but have short life when used at extreme rpm's-

Fixing this means no cage; & having the rod contain short rollers to not move side to side on c pin as motor runs-

Does the rod need rollers that are as wide as used now? I think not- prob. rollers about 30-40% as wide as presenty used would be adequate- & a lite rod design to contain the rollers-

These are cheap motors. There are no easy cheap answers to the next level of performance-

Hope this helps-

Thanks

Dave Richardson

RPMInc(ret)

Two:

 

[Les Smith]

My comments are highlighted below no pun intended.....

Reading with interest this discussion, I will add a bit of info/my thinking-
I am no expert & make no claims to be:
I think I know a bit about con rods both bushed & roller types from my years of making all types of these parts for nitro & petrol motors- One must know thoroughly all aspects for making rod assemblies in a gas engine that is capable of 20,0000 + rpms. Were these petrol roller rod bearing engines and bushed nitro rod bearings running 20,000+ rpms?
Grahame you know my thoughts here from our weekly chats via Skype-
My thinking on this goes as follows:
First: at the rpms these motors are being pushed to, motor balance scheme is critical (VERY)- rework of parts involved to be light & strong enough will help lighten loads on bottom of the rod/bearings- parts life is short if overstressed by imbalance- The most contributing factor is the metallurgy and the clearance not the imbalance.
Two: oil content & type/blend/oil percentage in the fuel used is of prime concern for decent rod bearing life- The oil used is a crutch for mis-alignment, excessive clearances and poor assembly.
Using a collet drive cable system is not good for motor/rod life- The thrust on the crankshaft is not a factor of rod failure..it is a fact of excessive play of the crankshaft in the case and mis-aligns the rod in relation to the crank pin and possibly rubbing on the crankshaft counter weight areas at high rpms..
These first two areas are fairly easy (?) to work on....
Now the hard part-
Three: these motors need pressure oil feed to the rod bottom end- not a lot but more then gets there in the present scheme/setup- They do not need oil pressure and to see that come to the forefront is a very long time of happening anytime in your grandsons' sons' lifetime
Four: The present rod/roller will be better I think if narrower/shorter) rollers are used- long un caged/crowded are limited to XX rpms if they don't stay parallel to the crank pin axis; to limit roller angling means very tight tolerances for correct assembled running specs. Narrower is the wrong direction to go, since the needles will have more of a load on them and not dispersed across the needle contact area.
This also means not enough space for right amount of oil for good lubrication-There is plenty of space with more needles using 12ozs of oil to a gallon.
Caged bearings work well, but have short life when used at extreme rpm's- Is extreme rpms 24,000 for a gas engine? if so then the clearances need to be tighter than what they are and the proper metallurgy is also required.
Fixing this means no cage; & having the rod contain short rollers to not move side to side on c pin as motor runs- Shorter needles will skew more than longer ones as well as better alignment is required with the complete assembly from the cylinder CL to the crankpin as well as a needle retainer that is of the right metallurgy and design to keep the needles in alignment any skewing of a needle roller(s) generates a lot of heat.
Does the rod need rollers that are as wide as used now? I think not- prob. rollers about 30-40% as wide as presenty used would be adequate- & a lite rod design to contain the rollers-
These are cheap motors. There are no easy cheap answers to the next level of performance- The gas engines of this size requires a precise needle cage assemble with the proper metallurgy and clearances for them to survive at rpms of 20,000 and beyond.Smaller needle width add more strress on the needles compared to the longer needles that can distribute the load better.

Hope this helps-
Thanks
Dave Richardson
RPMInc(ret)











Two:

More to come....

 

[dwilfong]

Drawn cup full complement needle bearing pressed in to the rod?

1-Shorter needles

2-needles controlled by the rod

3-more needles to make up for the reduced load carrying of the shorter needles

4-hard ness of rod not as critical as the race is the cup

5-no cage to worry about

6-may press into existing rod

Any thoughts?

 

[GRAHAME HAINES]

Hi Guys some more god stuff information/ theories coming out now.

LOHRING thanks for your oil content. 8oz per gallon is 16:1 (what I have been running) and 10oz is12.8:1.

I agree more oil gives a better piston seal wether ABC(nitro engine) or ringed as in our gassers. the down side of more oil can lead to increased ring wear as more oil forces the rings firmer against the liner wall.( Kart racers have been thru this) the trick is to find the right balance for best lube and cooling as oil is a coolant as well.

I agree we do not get a lot of run time on our engines.

As long as my backside is pointing to the ground and I am breathing fresh air, I will argue and stick by my belief that powerboat racing (wether full size or models) is the cruellest of all motor sports on engines. Most other facets of motor sport have a constant load on their engines when racing however we have this load unload scenario going on when the prop leaps in and out of the water when racing.

We are getting anywhere from 20000-25000rpm readings on our rev counters and to me that is the unload rpm you are getting. the loaded rpm can be anything from 1000-2500rpm lower than that depending on the current situation.

For guys new to the sport and reading this thread let me explain my situation.

For pretty well all of my 40years in this sport I have set my tuned pipes according to Gordon Jennings formula measuring from the piston edge down the CL of header and pipe to the mid point of the rear cone. this is whether I was running nitro back in NZ and now with gas here in Aussie. It applies to all 2 stroke engines. I use 1670 feet per second wave speed.

The other night I took my backlash for a run with the pipe set for 17000rpm. Did 2 runs and the taco read 18230 and 18320 respectively.

You have the engine doing 1700 in the water then it leaps out and instant rev increase coz it has no load then it is wack back in the water and back to 1700.

How many time have you heard of car racers popping an engine coz they missed a gear and over revved it.

I pulled the Jug off it after that as it has had about 10 runs since the last inspection. The big end bearing still looks like brand new thank god.

We have the last race of the season for the club cup and who ever wins that race is going to win the cup. the points are that close. So I need that engine to hang in coz the Gizmo is down

KEVIN I agree 100% on this one with you here. Unless the crank and be shimmed what ever to stop end float and keep it centred in the centre of the bore we can have issues.

Next time you are at a full size boat regatta poke your nose into their hulls and you will see the thrust is taken on a thrust block up in the centre of the hull usually close to the COG. definitely not on the engine as we do in a lot of cases. they do not take the thrust on the strut either.

DAVE and LES

Les You have not disclosed your age on your profile but I am 61 and Dave a smidgeon older

We go back to the 80's when Dave started making rods for our nitro engines.

We both have seen a huge amount of change in technology and metallurgies in our sport.

you both have good suggestions and there is often more than 1 solution to a problem and like setting up a good race boat often a host of small things combined makes up a good set up rather than one big thing.

I have to agree with Dave on the balance thing. that is pure physics. yes Les while I agree metallurgy has a big bearing on things here so improving balance will contribute to better life as well.

Look back to when K&B made engines. Their 6.5 engines were the new breed of marine engines as most of us were running water cooled model airplane engines.

That motor was a shaker and they recognised the problem so when the 7.5 was developed it got a tungsten weight put into the crank web. It was a big improvement over the 6.5 and things did not shake to bits in the boat the same after I put the 7.5 in it.

Les your comment about oil being a crutch is a bit provocative isn't it?

All engines need oil for lube and cooling. Even with correct alignment and clearances if you don't get the right type of oil, and,the mix right the thing is gonna go BOOM!!!!

I have already viewed my thoughts on thrusting on the crank above. My Zen has more end float (.200) than the Gizmo that had virtually none.

Pressure oil feed is another way of guaranteeing a constant supply but the mechanics of getting this set up working in practice in our boats is going to be difficult.

The rest of the comments comes down to metallurgies and clearances so I guess till someone can try these theories we are guessing.

DAVID now there's a thought cupped rollers same scenario as is used in our struts if you use needle rollers down there.

Only thing that has me concerned about this bearing is how do we lube it we are going to have to have a slot or hole in the cup to let the oil in aren't we?

Thanks for your input guys

Gotta go and put the jug on the zen and terrorize some ducks!!!

Grahame

 

[GRAHAME HAINES]

A big thanks to Bruce and the boys at Gizmo for the work on my engine.

The jug came back like new together with a new crank/rod plus piston, wrist pin, ring and bearings.

Ran it in last weekend and the backlash is boogying again. 19500rpm on both a gizmo 7016 in our small club pond and a COCR TH1+5 in my bigger test pond where the boat has room to wind up

From the discussion above I have decided to up the oil content to 12.5:1 i.e. 200ml to 2.5 litres of gas.

Hopefully the bottom end will be happier now.

Have one more race meeting here next Sunday then the Backlash is packed up for shipment back to NZ.

My Wife and I are heading to the USA for 3 months the first port of call the last 2 days of NAMBA Nationals so hopefully can catch up with some of you contributors above there.

Regards Grahame