Engine Busted - what went wrong?

[Mazon]

Hi guys ,my tt50 engine just busted, posting what happened to get some opinions as to what may cause it.

History:
TT50 engine been through 16 gallons on CP15%.The last time i opened up the engine was 6 gallons ago to change bearings. Engine was performing fine. Engine was tuned to hold back plate for 3~4s, hardly any lean runs. Normal curve headspeed ard 1650. idle up curve ard 1950.

What happened just before today:
Last sunday, i took out the engine to install a gov. So took the chance to change the bearings. since i was at it i thought might as well do some cleaning up. The piston had some carbon residue on top and a ring of slight brownish patch around just below the ring. Are these signs of lean?

The cylinder sleeve has some black patches at the exhaust ports.

So i use scotch bite n clean away the residues on both the piston n cylinder. took out the con rod n clean the inside of the piston also.

Changed both the bearings and assemble back,everything looks ok. turn the crank shaft by hand it was normal, no signs of binding.

Here's some pics of when i change the bearings.

[Mazon]

Today:

First flight - richen the engine abit as bearings are new. Flight was mostly hovering and slow figure 8 using only normal curves to let it run in abit.
Felt it was smoother then before i change the bearings. back plate temp was cool .So i thought all was good.

2nd flight - started with normal curve , flew around landed n tested back plate, temp ok. then switch to idle 1. headspeed higher. responsive and quite good power, so i thought great the bearing change works.
Then i test the rev max on idle 2. i set the limit too low so proceed to land n increase the limit.

I throttle up again on my normal curve, while hovering at eye level,can hear the engine start to get higher pitch like leaning out. then followed by metal sounds then engine cut...

i thought it was the fan came loose. When i came back, realised the con rod broke n the engine case got 2 holes!!

Damages:
-con rod broke, piston sides broke, engine case chui with 2 holes

-cyclinder looks ok.the rest of the engine looks ok except for scratches inside the casing.

Need experts' opinions...
Anyone else have this happen before? what could have caused it? Kindly share ur experiences so that wont repeat this again.

haiz sad...

[Palladine]

Was the piston stuck on the cylinder sleeve ?

If yes than it can attribute to your broken con rod.

If not, it can be that the conrod gave way due to metal fatigue. As the crankcase is punched it is due to the con rod piercing thru.

[Art2]

That looks bad, I've never knew an engine can have it's case being blown out. Hope your heli is ok.

[viperviper]

Connecting rod failure can be caused from trying to start the engine when it is flooded (hydrolocking), running too hot or too lean, too low of an oil content in the fuel, normal wear, over rev and lastly possibly a manufacturer's defect.

looks like a too lean situation from the piston burnt mark...causing stress in the rod material.

[Brandon Chng]

simple, just get an os50 hyper and run slightly rich. literally threw my TT engine away many many years ago. its hot and lean if you can hold your finger there for only 3-4secs.

[Art]

2 things....

cp 15%...which has lower oil content

and your cleaning of the carbon residues with scotch brite

[Cycross]

Mazon,

From RC car experience, when one changes the bearings, the other usual item to change despite whether wear or otherwise, is the conrod.

The play allowable at the conrod bushing is very miniscule, but due to the stress involved, makes a big difference.

Not to say that this is the actual root cause of your engine failure, but it brought to my mind the above advice from the car folks to me last time.

I hope this might help you.

rgds.

[Fit]

Looks like the conrod just failed due to wear and tear. Just a coincidence that it happens after your bearing change. After 16 gallons i guess checking the conrod's play is in order. The other time when I changed bearings I also checked my conrod's play with WY's newer engine for comparison.

Doubt its the fuel either. I have been running 15% since I started. Now 10% with no shims. Budget fuel!

[greenhorn]

its time to buy os50sh..it a waste do fly with tt50 with ur skill...go buy new os..up for u bro

[Murdanny]

Looks like the conrod just failed due to wear and tear. Just a coincidence that it happens after your bearing change. After 16 gallons i guess checking the conrod's play is in order. The other time when I changed bearings I also checked my conrod's play with WY's newer engine for comparison.

Doubt its the fuel either. I have been running 15% since I started. Now 10% with no shims. Budget fuel!

but it is really advisible to run your engines especially helicopter at least on a 15%. do take note that your engine is running constantly at high rpm when you are on idle up, thus lubrication for longer lasting engine is important (and of course tuning) to maximise power.

Danny.

[Murdanny]

its time to buy os50sh..it a waste do fly with tt50 with ur skill...go buy new os..up for u bro

yeah! agree agree! upz for u too!

[Fit]

but it is really advisible to run your engines especially helicopter at least on a 15%. do take note that your engine is running constantly at high rpm when you are on idle up, thus lubrication for longer lasting engine is important (and of course tuning) to maximise power.

Danny.

Thats true regarding the lubrication. With lower nitro you need to run it leaner to get the same amount of power meaning less oil through the engine. If max power is needed then better to go to slightly higher nitro. For a backyard flyer, the lower nitro will suffice as long as the engine is not leaned out too much.

[Adrianli]

That looks bad, I've never knew an engine can have it's case being blown out. Hope your heli is ok.

I have witness an engine the size of a family car blown open wif con rod + bearing flying everywhere. Also read abt engine the size of a 3-storey building having a crank case explosion, so its mandatory to have a oil mist detector in these engines.

But the explosion is nothing like u see in hollywood movies lah. No fire or flame, jus parts flying ard.

[Murdanny]

Thats true regarding the lubrication. With lower nitro you need to run it leaner to get the same amount of power meaning less oil through the engine. If max power is needed then better to go to slightly higher nitro. For a backyard flyer, the lower nitro will suffice as long as the engine is not leaned out too much.

Dun you need a higher oil content, as you are running a revmax governor on it? The engine can last long?