Engine Failure

[GRAHAME HAINES]

I have been racing a Gizmo 30 in an 18 lb backlash over in west Australia and have had the big end bearing cage let go .

Has anyone else had issues with the Tiger king crank big end.

I run 91 octane pump gas with Castrol racing A747 oil @ 16:1

Engine has 3hrs 21min run time and tacho regularly reads 18750 to 19500rpm pulling a gizmo 7016 with 4.3 pitch.

first 2.5 hrs ran the gizmo victory pipe then switched to the new CC racing monster v2 pipe that seems to have improved the bottom end torque till it went boom.

Any comments greatly appreciated

Grahame (birthday Boy)

 

[Ray Sametz]

Gallon of pump gas UK 160 oz. or US 128 oz. ???

 

[larcor69]

JUST sometimes things let go, hot rod engines are prone to fail eventually, these weedwacker engines are pushed way beyond what their designed for,, get ceramic bearings fome cc, about the best you can get, Happy Birthday too!

 

[GRAHAME HAINES]

Thanks Larco

I figured I may have got a crank with a Monday or Friday bearing in it.

After 40 years in the sport running nitro have had the odd failure with newish bearings that are unexplained.

I was curious to know wether it was an issue with that crank but have not been inundated with replies so looks like a 1 off.

My case bearings are fine (4brg Gizmo Billet case) and they will be up graded when I get the parts back from Bryce.

As for ceramics on the big end we would have to get the engine manufacturers to install them when they assembled the crank.

the average Joe Bloggs doesn't have presses and jigs to disassemble and reassemble cranks

Ray I don't quite follow your reply.

We use litres over here and 16:1 is 250ml to 4 litres of gas.

 

[Lamar_Huff]

I can't speak specifically to the Tiger King crank as I only have a few of those (so far), but... In 12 years of racing gasoline powered Zenoah's I would venture to say 9 out of every 10 failures is related to the bearing on the big end of the crank. It seems to be the weak link in these engines...

Thanks,

Lamar

 

[LarryBeals]

When your running in water some is going to get

Inside 1 rust pit high RPMS will take out bearings

 

[Andy Brown]

3 hrs 21 min at 60 mph. That's about 200 miles! IDK, but I'd say that is time to rebuild a high powered race engine. A heat race plus mill time laps is about 2 miles, so that would be 100 races. What do we expect from 4 HP per cubic Inch at the cost of a mere $700?

 

[Les Smith]

The stock crank pin bearing in any of these engines which rpms are sustained at 18k+-19k+ rpms even with a slotted rod is surviving on the outer limits of reality and borrowed time. Increasing the oil to 16 ozs per US gallon will help the longevity and of course pitted bearing races from water ingestion or from dunking ... the engine is then a ticking time bomb ....although one should tear down and inspect their modified engines regularly, which is a preventive maintenance that helps to prevent a major engine failure.

 

[lohring]

Les is being modest. He is developing rods and bearings to address this issue. I wrote about the problem and suggested solutions in Big End Blues in the NAMBA Propwash. Les is actually selling parts.

Lohring Miller

 

[dwilfong]

Les remember when I showed you this.........

Ran the same bearings for about 2 years of running every weekend and racing.

GALLONS of 60% nitro thew my CMB 1.01 at 26000+ RPM..................................

The large bearing is the same one used in the gas eng.........................................

Thy are still in the eng to this day.............................................

Greg Settle knows his stuff when it comes to bearings.

Build the right bearing and it will live..............................

 

[dwilfong]

http://www.rusengines.ru/?content=content.php&lang=en&lang_upd=en&cover=green&cover_upd=green&USD=31.56&EUR=42.01

(To help clarify what I am talking about.)

In sale the experimental batch of piston ceramic fingers from nitride of silicon Si3N4 has arrived.
The sizes ∅4-0,005 х 13-0,05 mm. Are applied to motors 2,5 cm3: F1C, F2A, F2C, F2D.

The basic advantages in comparison with steel fingers:

Has no internal aperture.
Weight 0,5 gr., as relative density 3,2 gr/cm3 (weight of steel 1,0)
Durability of 990 kg/mm2 (A steel of 220 kg/mm2)
Hardness Hv 1600 (a steel 800)
High rigidity - the module of elasticity 32... (At a steel 20...)
Factor of a friction with greasing 0,01...0,02 (a steel 0,04)
Factor of a friction without greasing 0,03...0,05, (a steel 0,1)
There is no "winding" of a material of the piston on a finger (it is not tinned...)
Working temperature to 800 0C constantly, 1600 0 - it is short-term
Admissible speed of heating 800 Degree a second

Use of such finger as a neck for a modular cranked shaft is possible. Further manufacturing of fingers of other standard sizes is planned. We accept orders for piston fingers, rollers for the bearing of any size in diameter from 0,5 to 50 mm.

This is some older info from 2010. Wonder where this has gone since then?

 

[GRAHAME HAINES]

there has been some interesting scenarios posted above.

First eliminate the water in the bearing .

My engine has only been upside down once first thing in the morning during a practice run on race day.

When I pulled the plug back on shore it was dry. Obviously I was tinny enough to get it shut down before it swallowed a guts full of water

40 years of running nitro hydros taught me a thing or two about making waterproof cowls that give you time to kill the motor before ingesting water.

It got a tank full straight through it then 6 races plus a couple of runs after racing so I doubt there was any moisture in it to cause the failure.

Run time. no way has it run 3hrs 21min at full throttle more like 60% of that time would be hard out.

Bench time ,mill time at around 1/2 throttle and I do a good minute of that to give the engine time to get the temperature right not to mention getting the brain right are included in that time.

Dwilfong has showed us crank shaft bearings of a nitro motor. As I already explained above my bearings are like new.

its the big end Cage that has failed

If we could somehow encourage our engine manufacturers to install the best bearings available on the market in these high stress areas maybe we would have less failures.

 

[Les Smith]

David- I remember the crankshaft case bearing you showed me within the last year, however this thread discussion is about the connecting rod and the connecting rod's piston pin and crankshaft pin bearings, otherwise if the topic was about bearings in general the crankcase bearing that Greg Settles made for you will fit right in as well as Greg Settles never made any of the needle bearings for the connecting rod or for the piston pin type of bearings as being discussed here.

The high rpms of these engines are surpassing the connecting rod crank pin bearing's assembly (the setup is too loose), since the higher rpms (19k+) require better metallurgy or at least a tighter tolerances to survive the high rpms.

....so how is one going to make it survive?...very rarely does a crankshaft case bearing fail in comparison to any connecting rod bearing.

 

[lohring]

Big end bearing failures are usually cage failures. When the cage fails the rollers skew and the rod comes apart. The solution is a combination of things. Jim Allen's design principles from Big End Blues:

1. The rollers must be well aligned. Loose needles won’t work. If the rollers can skew even slightly, the bearing fails.
2. Roller skidding can be prevented with tight clearances (.0003 to .0005 inch), slightly rough (10 to 12 micro inch RMS) surfaces, and low cage mass.
3. The rollers have spherical ends so the cage can have very well rounded corners for lower stress.
4. Two rollers can run in each slot giving more bearing surface and low cage mass. Rubbing doesn’t seem to be a problem.
5. The cage must pilot on the rod bore. The separators are wedge shaped and contact the needles at their center line. This style won’t contain the rollers for assembly, but will self center and guide the rollers better with low mass and friction.
6. The rollers and crank pin must be hard all the way through. Surface hardening leaves a lower strength material just below the surface that can fail. Jim uses hardened reamer blanks made from M-2 high speed steel.
7. Cage strength is very critical. After trying several materials, Jim settled on C-350 maraging steel. It has very high strength and holds its dimensions well after heat treating. That allows nearly all machining to be done on the soft material.
8. Additional oiling is needed. An oil slot in the bottom of the rod helps.

Below is a picture of that type of bering on a Zenoah crankshaft. The second picture shows the start of a cage failure in the stock bearing.

Lohring Miller

 

[Les Smith]

Here are some more pics of the bearings that we made and the new connecting rod.

Bearing Retainer

New Rod

 

[dwilfong]

Well the funny thing is every one said that a full complement bearing would not work on the main bearings.

Its is the same bearing used in the gas eng. Its not just for nitro.................YA that old nitro gas thing....LOL

Many have tried with the old steel balls and it was a failure.

My point is.............That a full complement dose work...........................

With the right materials and the proper clearance..............

If I have listened to every one and not tried it I would have never found out how good it works.

Now what I am trying to get across is try it in the rod with the ceramic needles..............

You can discredit it all you want and give explanation why it will never work................

BUT IF YOU DO NOT TRY IT.....................you will never know........................................

Would be much easier to do than reinvent the crank and rod...........................

The cost would be minimal and the labor to do..................................

But then again it is much easer to just put you head in a hole and ignore it also........

SO put your books away and give it a shot .....You may learn some thing new.................What do you have to lose..............

Swami .................out....................

Dam I wish I would have listened when every one and all the books told me a 2 stroke eng will not run with out a intake valve.....LOL

 

[lohring]

Dave, have you tried a full complement bearing in a Zenoah? It should be easy if you or a motorcycle shop could disassemble a crankshaft and reassemble it accurately with needles from several stock bearings. You would need hardened steel washers to space the ends. The alternative would be new, longer needles. I believe they could be cut from reamer blanks. My experience with a 36 mm bore, 30 mm stroke build was that a longer rod was also needed. After the 50 mm rod big end turned blue, we went to a slotted 55 mm rod. The stock bearing is still alive, but the engine only gets run in special races.

I still think that a cage is needed to prevent needle skewing. I have run nitro engines with full complement bearings. These engines don't develop the torque of gas engines of similar power. When we tried to dyno several 11 cc nitro engines, we melted their pistons. Gas engines from 2 to almost 12 hp have been dynoed with few problems. That includes running gas engines on nitro fuels, though we managed to melt the electrodes off the plug in one test. An 11 cc nitro engine should have around the power of a stock 26 cc Zenoah, but we didn't get a complete run to prove it. .

Lohring Miller

 

[dwilfong]

Lohring

I have some thoughts why the full complement was successful in the main bearing.

The ceramic balls used where of the best quality available. The surface is almost perfect on them. This leads to less friction. also the balls are much lighter. This enables the balls to not bunch up from surface drag and float in the race. This may also let them utilize the surface tension of the oil better.

Spinning up the full complement ball bearing you can see the balls finding there own.

Think about what makes the needles skew?

So do we try and bandage this with more control over the problem or try and reduce the problem?

The problem being friction. Witch produces heat that will compound on its self with steel needles after it starts.

Read the nomenclature comparison in the post I made from the Cyclon web sight.

It looks like if some one would contact Cyclon thy may be able to make what is need to test.

Just some thoughts................................

The main bearings have run in my CMB 1.01 16.6cc eng for 2 years now on 60% nitro and RPMs of over 260000 at times.

Before with other bearings including caged off the shelf ceramic bearings. I would not get much more than 2 gallons threw the eng before thy needed changing.

David

 

[GRAHAME HAINES]

Wow Some great information coming thru now which I was hoping for when I started this thread.

With David and Lohring's technical brains and Les's mechanical brain all working on this issue.

My Background is in earthmoving and when we have bearing failures in our machines there is usually a traceable reason. A failed seal letting in crud, Lack of lubrication (when operators get lazy with a grease gun) physical damage to the bearing itself or elsewhere that causes misalignments with shafts etc. and consequent failure

My Original post was to find out if it was peculiar to the TK crank and obviously not. Zens have the same issues. There has to be a reason and it maybe of my own doing in this case. Who Knows ?

Les and Lohring have shown an answer with a better constructed bearing with a better fit for the Zenoah crank . Obviously the fit of the original bearings are not as tight as they could be.

Maybe the TK crank is the same..

My Next issue is Oil content. am I running enough at 16:1.

Les suggested 16oz to the gallon will help so I figured we used to use imperial gallons over here and in NZ before we switched to metric litres in the 60's and we had 160 ozs to the gallon so that equates to 10:1 !!

Then I Googled a US gallon and find you only have 128oz to the gallon so les's recommendation is 8:1 Double what I have been using.

Maybe here in lies the problem.

I purchased a 29.5 stock Zenoah to run in the Backlash before I bought the Gizmo 30. It is my first venture into Gas.

The booklet supplied with the motor by Zenoah recommends fuel mix of 25-40:1!!!!! (Thank god I didn't go with their recommendation)

I asked the question at our local club and as well searched IW and Jims Boat Dock and 16;1 seemed a good number people were running so I went with that.

I now wonder how many poor sods, that are not hooked into a club or these forum have gone and bought a boat and a new engine to do their own thing. Go with the Zenoah recommended oil mix throw on an expansion chamber to get more revs and power and promptly blow the dam thing up thru lack of lubrication.

I have limited tools to work with here in Perth( All mine are in storage back in New Zealand) but I do have a battery powered dremel so have lifted the exhaust timing to 180 and the induction up to 160 degrees on this engine . The transfers are stock as I can't get the wee grinder in there to do them properly so left them alone till I get back to NZ. It is pulling 17500-18000rpm on the gizmo pipe. It prefers that to the CC monster V2 pipe. Maybe coz it is a smaller volume?

Me thinks I will be running more oil from today and hope I have not hurt things too much on this engine.

Its a lot harder to check Big end bearings on these things compared to a nitro motor.

The great thing about this hobby is we never stop learning no matter how long you have been at it.

So what do you experts think?

Cheers Grahame

 

[Les Smith]

There is less friction with a ball bearing due to the contact area compared to a needle bearing and the needle bearing can carry more of a load and as a full compliment needle bearing it will have the highest skewing, sliding and heat generated compared to a properly caged needle assembly or a ball bearing for high rpm use.

When I talked to the engineering group at Schaeffler / INA Bearing a few years ago the full compliment needle bearing will not survive on a crank pin at high rpms....there are best used for universal joints in cars and trucks

There is no controlling or band-aid fix for a sloppy bearing assembly only proper metallurgy and clearances are required to stop skewing and pounding of the bearing from excessive clearances. Needle bearings require a proper cage assembly to guide the needles, which stops the skewing at high rpms...all bearing needles and balls will slide at or above a certain rpm where there is an oscillation of the rotation direction as with a connecting rod bearing on the crank pin.

David - Why not get someone to make you a full compliment ball bearing for the crank pin and then try a full compliment needle bearing on the crank pin and let us know how it turns out.