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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine
 
 
Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

Rotation

Also consider that your engine might be starting the opposite direction and the clutch engages imediately. Even if your starter turns the right direction, you could have a back fire and make the engine start the other way around.

Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
03-30-2006 Over year old.
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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Tivo,

I think you might have been on the money here about the bearings. Earlier today when starting it i noticed that every now and then the engine would not turn over for one or two revolutions of the starter and my initial thought was that the starter shaft was slipping in the starter. About 20 mins ago i went to start it again and then something failed completely. For about every 10 revolutions of the starter the engine turns over once and now the starter hex coupling has become MUCH more difficult to turn in BOTH directions. This points to a failed bearing somewhere i would think. I apologize for so quickly dismissing your advice because i have a feeling this will be the source of my problems when i find out what it is.

Now i need to go find out if the whole pinion stack is compatible with raptor 90 parts. Im thinking im going to replace the whole thing including bearings, starter shaft, bell, pinion and clutch.





A day without sunshine is like, well, night.
03-30-2006 Over year old.
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Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

VAriable timming

If you are able to retar the timming a few degrees after TDC your starting would be easy.

This was my most awaited feature of the Webra, assigne variable timming to a switch like trottle hold and fire away with a normal starter.

It should be a walk in the park(or flight in the park)

Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
03-30-2006 Over year old.
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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Uh... you are talking way over my head now





A day without sunshine is like, well, night.
03-30-2006 Over year old.
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Franconia2
Heliman
Location: Shrewsury, MA

Anni,

I feel for you man... don't give up.

I find the idle speed on this engine to run very low, it has never engaged the clutch nor has it ever stalled due to too low rpm on my X-Spec. Is the low needle too lean? What if you richen the idle needle, it will slow down the idle.
Filipe may be right, the engine may be starting in reverse. Is the rotation of the clutch bell in the correct direct to engage the head?

Dave
03-30-2006 Over year old.
 
 
avator
Veteran
Location: New Jersey

Felipe,

I think if you sent the timing past TDC it won't run. It has to be at least a few degrees before TDC to idle. I do agree with your assessment that it sounds like Anni's motor is either running backwards or the bearing is upside down or defective.
03-30-2006 Over year old.
 
 
Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

TDC and Timing

From my limited knowledge, if the spark is before TDC, then you run the risk of back fire, It has to be at TDC or past it. I may be talking about even less than one degree. I know if it is not exactlly it wont produce power, but it will fire up and as soon as you click the switch it will return to normal timming.

Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
03-30-2006 Over year old.
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AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Well i took it apart and the bearing in the clutch is shot completely now. It has torn up the starter shaft enough and worn a groove that it was a bit hard to take it out and when i did get it out a pin from the needle bearing / one-way fell out with the starter shaft. Before i took the shaft out i attempted to spin it in BOTH directions and although it was very rough turning in both directions it indeed did work both ways. Thats definetly bad. Now the question in my mind is was this the CAUSE of the problem or the effect. Im tempted to replace the whole pinion stack and bearing blocks, clutch, clutch bell, etc but i will probably first try just changing the shaft and clutch / one-way and see what happens. Ive tried to think this through to think if the symptoms i was getting could be caused in full by a malfunctioning one-way on its way to a full failure and im still up in the air on that. I'm afraid that this may have been the effect of some other problem in that area which is manifesting itself with the clutch problems and now the bearing failure.

As for the engine direction, i can say with 100% certainty that everytime i have attempted to stop the clutch bell with my finger while the engine was running - it was spinning counter-clockwise which means the engine must be running that way as well and to my knowledge this is correct for a heli whose blades spin clockwise. Ive also noticed that at least the top bearing in the bearing blocks is notchy. Not completely bad but definetly has some dirt or grit in there causing it to not be completely 100% smooth.

Should i start with just replacing the failed parts first? Shaft and clutch/one-way before i sink much more into it? Do you guys think that a failing, bad, or wrongly installed one-way in the clutch could have exhibited all the symptoms i have described or is there a possibilty in your minds that the failed one-way could be a because of something else not right.

This sure is a whole new ball game for me One thing is for sure. If your first build of something new is a pain in the butt the next ones will be a breeze. I thought this was going to be fast and easy when we got the engine mount sorted. Who would have guessed id get hung up on something this silly.

Im NOT GIVING UP! This thing WILL FLY !





A day without sunshine is like, well, night.
03-30-2006 Over year old.
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avator
Veteran
Location: New Jersey

Anni,

If you have notchie bearings replace them. They can cause radio glitches. Usually, when they feel notchie, it is not dirt, but, rough balls or race. No sense taking it apart and not replacing the bad bearings. Was this heli crashed? That's what usually causes bearings to get notchie.

Felipe,

You are somewhat correct in you thinking, except, if the plug fires close to, or after TDC, there is really no time for the fuel to ignite and push the piston down. If the timing is set to about 4 degrees BTDC it will never kick back unless you flip it really slow and then at that setting it is a mild push and not a real hard kick. Most model engines with fixed ignition have a compromised timing setting at somewhere around 20 to 24 degrees BTDC so that the motor will run OK at idle, as well as, full throttle. When the timing is that far advanced that's when kick backs can and do occur. With adjustable timing you set it at 4 degrees BTDC and at high throttle 30 degrees BTDC. This gives you easy starting without kickbacks and a really slow steady idle and then you benefit at the top end with a little better performance from the extra advanced timing.
03-31-2006 Over year old.
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Avator,

Never crashed but its been sitting in the box around the house now for over a year while i made up my mind if i was ever gonna start flying gas or not. That bearing could have been bad from installation for all i know. TZ's come 90% RTF and i only rebuilt the head and re loctited the bolts in the frame.





A day without sunshine is like, well, night.
03-31-2006 Over year old.
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avator
Veteran
Location: New Jersey

Anni,

If it's new then the bearing notchiness is probably grease that has hardened. You might be able to clean and relube them. If you can't get them smooth I would definately replace them.
03-31-2006 Over year old.
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

All new parts will be here tomorrow. Hopefully there is time to put them in. Replacing the entire section including bearings.





A day without sunshine is like, well, night.
03-31-2006 Over year old.
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Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

timming

Avator:

Do you know of a site that explains it better? This is the main reason i want to change to a 12ZHP radio with the new webra gasser, as i could set a seperate mixing curve(timing) vs. Throttle or pitch. This would give me easy starts, excellent idle and maximum power at full stick. Im very excited about this new engine.

Thanks
Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
03-31-2006 Over year old.
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MRS
Heliman
Location: Netherlands

Ignition timing.

Let's be carefull explaining timing of gasser engines. There is not only the spark before TDC. It depends on the shape of the combustion chamber, the caracteristics of the muffler, the compression ratio and so on. For every brand gasser engine it's a different thing. As Avator explained, the spark should be there before TDC. What you want is that the mixture burns fully before the ports of the outlet opens. On a two stroke the advanced timing has to be earlier in comparison with a four stroke. Simply because there is less time. This combustion takes a certain time. this is why the timing has to be earlier on higher RPM. The time between TDC to opening the outlet ports is smaller on higher RPM, therefore the ignition timing has to be earlier. It's before TDC to start the flame traveling (the pressure buid up is not there yet) and get fully pressure build up at or just after TDC. If the timing is a little to early the pressure build up is so high the piston by it's kenetic energy with the flywheel, can not go by TDC (to high pressure build up) and backfire occures.

If you don't know what youre doing, stay of the timing, because this can distroy the engine easely, with bended connection rods as a result.

Well, I can go on explaining, but it's complicated. My enlish is a limitation in that.

Marcel
04-01-2006 Over year old.
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Chris Bergen
Key Veteran
Location: location

An excellent explanation, Marcel.

Chris Bergen
04-01-2006 Over year old.
 
 
avator
Veteran
Location: New Jersey

I thought so as well.
04-01-2006 Over year old.
 
 
avator
Veteran
Location: New Jersey

Felipe,

Most modern electronic ignitions are available with automatic adjustable timing based on engine RPM's. It is absolutely unnecessary to try to control the timing from your radio. Early electronic ignition systems used throttle coupled spark advance that worked quite well.

While it is possible to damage an engine with the wrong timing settings, most engines that we use on our models are quite happy at 4 degree's BTDC at low throttle and 30 degrees BTDC at high throttle. As MRS has said, there are many factors that determine proper timing settings, compression ratio's, fuel octane, 2 stroke vs 4 stroke, to name a few, however, I have been using the settings above with good results for years with many different 2 stroke model engines, including, converted glow engines, such as, Super Tigre and OS. Works for me.

Felipe try this site, www.ch-ignition.com
04-01-2006 Over year old.
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

If anyone is still interested (after all the timing talk), Marcel and i were able to finally get this thing ready for a test flight today. YAY! No flight yet but we did spool it up a bit (inside in the emtpy next door apartment). I've replaced the entire starter and clutch system with raptor parts and things are running smooth finally and as they should. If weather permits we will have a flight or something near that tomorrow i hope





A day without sunshine is like, well, night.
04-01-2006 Over year old.
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MRS
Heliman
Location: Netherlands

Finaly

Thanks Chris. I did my best. And yes Anni, everyone on this thread is interested. It's finaly running like it should. Now, keep it together and enjoy it!!!

Marcel
04-01-2006 Over year old.
HOMEPAGE  
 
 
AnnihilaT
Key Veteran
Location: The Netherlands Force: The Dark Side

Its flown today! Only a very short test hover as the wind was beafort 6!!! Yes, i could no longer wait but it was quite scary since this machine had never left the ground yet and being that its my first large fuel machine. I tached almost 1600 rpm at 65% throttle and 0 deg pitch. Franconia, could you maybe give an indication what kind of throttle settings you are using so i have some kind of comparison? I didnt check temps running the engine that high but will do that next time when the wind isnt threatening to blow me and my heli to the next city.

I also seem to have some kind of weird throttle glitch or a servo going bad or something. Now and then the throttle servo will jump forward on its own for about half a second and then jump back to normal again. I have watched it do this with my own eyes because at first i thought the revving engine was air in the fuel line or something but after watching it for awhile i could visually see that the servo is jumping forward and back. Any ideas if this is an indication of something specific? Its a 9252 on the throttle. PCM RX.





A day without sunshine is like, well, night.
04-02-2006 Over year old.
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Gohbee Aviation Stinger 30-90 > Gohbee / TZ / Raptor 90 Heli with BME modified G90 Gas Engine
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