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Century Helicopter . MTA Hobbies . Model Rectifier Corp

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Gasser Model RC Helicopters > Rebuilt Gasser Problems
 
 
SteveH
rrProfessor
Location: Texas

After a major crash due to a plastic rotor head failure, I've rebuilt my X-Cell gasser and this time, with all the recommended pieces for a camera ship, which I also play around with, the metal head center piece, the aluminum upper side frames, and the upper thrust bearing block.

Now the thing takes an up elevator command with full power/collective and conversely takes a down elevator command with full power and full negative pitch while inverted. It also wants to baloon up while in fast foward flight with the slightest of up elevator command. I made no other changes to the control system. Is this an extra added function of the metal rotor head center piece?

The engine also seems to have less power than before at full throttle, however it's been in the 90's here for the last few times I've flown it, and that's probably the reason. Are there any changes I can make to carb adjustment or oil/fuel mixture that will compensate for hot conditions? I'm currently running Amsoil 100:1 oil and 89 octane gasoline (midgrade) mixed at 64:1, 2 oz. per gallon.

Thanks,
SteveH
06-05-2003 Over year old.
 
 
3dwanabe
Senior Heliman
Location: Concord, CA

Check your Paddles

The metal head block and aluminum upper frames will not cause the pitchiness problem. It sounds like your paddles may not be aligned properly.

I have read in this forum that 87 octane mixed 64:1 is best for very hot days. Last week I flew my X-Cell Gasser with Coleman camp fuel mixed 64:1(the only fuel I have ever used) on a 95 degree day with no change in performance compared to cooler days. I just had to lean the needles very slightly.

Roy
06-05-2003 Over year old.
 
 
SteveH
rrProfessor
Location: Texas

Roy,

Thanks for your input, but the paddles are aligned properly. I've even tried some other fatter and heavier paddes with the same results. The thing I don't understand is I made no other changes, the radio tray was not damaged, so no changes there, all the linkages with the exception of the rods from the swash to the mixers are the same. The only thing I changed that has any direct impact on flight caracteristics is the rotor head main block.

SteveH
06-05-2003 Over year old.
 
 
3dwanabe
Senior Heliman
Location: Concord, CA

Steve,

Have you checked the main blade grips for damage. When I first set-up my used Gasser I noticed a large dent on one the blade grips where the blade previously swung around and impacted the grip. I applied a considerable amount of bending force to the top half of the grip (blades removed) and found a split from the dent to the end of the grip.

Other things I would check:
Elevator swing arm and bellcrank
Gear teeth in elevator servo
Main rotor head dampner o-rings
Loose tailboom support mount


Roy
06-05-2003 Over year old.
 
 
SteveH
rrProfessor
Location: Texas

Yep, checked all those things and everything is OK.
06-06-2003 Over year old.
 
 
Billme
Key Veteran
Location: MS

Steve said:
>Now the thing takes an up elevator command with full power/collective and conversely takes a down elevator command with full power and full >negative pitch while inverted.

Are you bragging, are complaining here?



>It also wants to baloon up while in fast foward flight with the slightest of up elevator command. I made no other changes to the control system. Is this an extra added function of the >metal rotor head center >piece?

You need to check your CG....Also you need to add a little expo around center on elev if you don't use the sliding flybar weights..
Samething happen to me when I went to the all metal head...Make sure your paddles are paralell to the swashplate...With the plastic head, it was twisting, and giving you built in expo for a while till it broke...Now nothing gives, so it going to be more touchy til you dail it out...




>The engine also seems to have less power than before at full throttle, however it's been in the 90's here for the last few times I've flown it, and that's probably the reason. Are there any changes I can make to carb adjustment or oil/fuel mixture that will compensate for hot conditions? I'm currently running Amsoil 100:1 oil and 89 octane gasoline >>>(midgrade) mixed at 64:1, 2 oz. per gallon.
>

Cut your oil to 1.5 ounces, and richen up on the lowend... 90 deg heat zaps a gasser..It still effect the new engines, but not as much as the older engine
Where are you at on the needles right now?

Regards,
Bill





id:
06-06-2003 Over year old.
 
 
SteveH
rrProfessor
Location: Texas

Hello Mr. Bill,

I suspected you might have an input on this one, well, hoping actually.

Yes, the reduced oil mixture will be my next attempt with the engine. It's still running good, just seems to have noticeably less power on full stick climb out. My mixture settings now are 1 1/8 low, and 1 1/8 high.

About the control system, I do have 25% expo on elevator and aileron channels on hi rate, which is where the problem exists. Don't know but it may be there in low rate, just don't ever fly in fast foward flight in low rate. The CG is correct, even a little foward with fuel. How much expo do you use?

My next attempt at curing the elevator coupling with collective thing was going to be a mix. Is this what you use, or is there a mecanical setup problem I should look for? I've checked the geometry of the elevator system and found no problems that I can detect. The elevator push rod is exactly the same length as the swing arm forming a perfect parrallegram, which to my understanding of the system, is what is needed. The paddles are as perfect as my eye can see using paddle guages.

By the way, Bill, I tried to PM you about this, just knew you were dieing to hear, but your box was full! I know you probably have hundreds of us hangers on bugging you to death about gassers, but believe me we all do appreciate your time and efforts.

Thanks,
SteveH
06-06-2003 Over year old.
 
 
Billme
Key Veteran
Location: MS

About the control system, I do have 25% expo on elevator and aileron channels on hi rate, which is where the problem exists. Don't know but it may be there in low rate, just don't ever fly in fast foward flight in low rate. The CG is correct, even a little foward with fuel. How much expo do you use?
------------------------------------------------------------------------------------------------
I use about the same expo…you might have to try a little more nose weight, if you don’t want to turn down the throws…



My next attempt at curing the elevator coupling with collective thing was going to be a mix. Is this what you use, or is there a mecanical setup problem I should look for? I've checked the geometry of the elevator system and found no problems that I can detect. The elevator push rod is exactly the same length as the swing arm forming a perfect parrallegram, which to my understanding of the system, is what is needed. The paddles are as perfect as my eye can see using paddle guages.
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But are your paddles parallel to the swashplate ?
You might want to check your ball distance for, and aft on the swashplate . Check from the center of the mass, to the center of each ball …If these are not equal distance, it will cause differential on the elev throw from the elev lever below the swashplate …Check the lever also for a bent standoff too. It doesn’t take much to be off..




By the way, Bill, I tried to PM you about this, just knew you were dieing to hear, but your box was full! I know you probably have hundreds of us hangers on bugging you to death about gassers, but believe me we all do appreciate your time and efforts.
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I’m just lazy Steve.. I cleared out my box…. Keep at it; I know you’ll find the problem
Regards,
Bill
06-06-2003 Over year old.
 
 
SteveH
rrProfessor
Location: Texas

Bill,

First, everything you said to check I've already checked and everything is good.

Just came back from flying it again and I did learn some things. First the fuel is now at 85:1 with 89 octane midgrade gasoline with the carb set at 1 1/4 low and 1 1/4 high and it's much better. MUCH better power.

I tried another set of blades, some OEM woodies and it was no better. Then I tried moving the mixers to the outer holes and this helped a lot. It's still not fixed but it's better. This tells me it is something in the head, and probably the damping. I assembled the head as per the instructions, but at this point I think I'm going to put additional washer/spacers in it and tighten it up and see what happens.

The mix I put into the radio is eliminating the elevator input with collective.

I'll keep you informed as to what I find if any thing.

SteveH
06-06-2003 Over year old.
 
 
Billme
Key Veteran
Location: MS

Your pretty sharp Steve, I'm sure you will hunt it down ...Sometimes its really hard to help folks trouble-shoot over the keyboard...
On the mixture, this is the reason I had much success on the old puh know ing the cooling was not the best, but using more fuel to help cool the engine, always works...
Good luck
Bill
06-06-2003 Over year old.
 
 
SteveH
rrProfessor
Location: Texas

UPDATE

I've updated Billme on this by PM, but just in case there are others interested, it's fixed. Come to find out, and anyone who reads instructions well (DUH!) will find out, that when converting to the metal rotor head center piece, you need to add washers to stiffen the damping. It also says if you add the metal piece and keep the stock plastic mixers, move the bolt to the outer hole.

It's flying very good now.

SteveH
06-10-2003 Over year old.
 
 
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Gasser Model RC Helicopters > Rebuilt Gasser Problems
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