Bergen Intrepid Gasser EB G26 800mm. DIRVEN TAIL?

[ILoveRC]

I am wondering if the driven tail upgrade is as strong as the stock nondriven tail main gear. The stock nondriven tail main gear is massive. Is the upgrade stronger than the stock gear? Or is the upgrade a different material and is the crown gear as strong as the nondriven tail crown gear setup? Hope my question is well understood. Thanks Mike Lewis from over at RR. "sure is quiet over there these days" lol

[ShawnK]

The driven tail gear setup is made from the same material as the standard main gear. In fact, they're the same gear... the driven tail setup involves additional machine work to split the main gear into a main gear and a crown gear (hence the name "split gear driven tail").

Be aware that in the "stock" configuration (i.e., not driven tail), if you have an auto and the tail blades touch the ground, you'll most likely not damage the gear. But, if you have the driven tail setup and the tail touches the ground at any point, you're virtually garanteed to have a stripped crown gear, because something has to give when the crown gear is physically pinned to the main shaft.

That doesn't mean that one gear is "stronger" per se, it just means that you're using it in a different application. The actual gear material itself is the same between both versions.

[cbergen]

Excellent explanation, Shawn.

The "new" main gear material that we have been using for well over 2 years now is actually stronger than the molded gear previously used.

If your having difficulty with stripping gears, it normally comes down to mesh or heat. Too loose of a mesh will take them out. Too tight will eventually wear in, unless it's so tight that heat builds up from friction, and melts the gear.

[ILoveRC]

Thanks for the description. I haven't had any problems with tail strikes or main gear problems persay . I have had a fair amount of difficulties getting the heli to remain flyable . The history would exceed the space allowed here for expsression.
I droppped the engine out to get a closer look at the clutch and the main shaft and main gear and that is when I discovered the bearings were gone in the main shaft bearings blocks. I have just removed the main shaft, and both bearing blocks, the clutch, and start shaft bearings. I put them in a box and sent them in for bearing replacement and for an examination of the clutch. The heli had about 1 + 1/2 to 2 hours on it at this time. The clutch got hot and I don't understand why? It just began to slip and the engine rpm needed to engage the clutch increased quite a bit I would say 2,500 to 3,000 before the clutch began to engage well enough to spool it up.
I have been running the NHP 800mm blades and I want to have the parts repaired so I can continue to fly the 800's. But I am going to try some 710's and so I want to get a setup so I can try them and see if I can get it to fly without the problems of vibrations and Elrctronic equiptment falures. I so much want a heli I can fly.

Thanks Chris You and Larry have been 1st. class people with me!
Sincerely Mike Lewis out in Arizona

[cbergen]

I thought the vibrations were cured when we switched to the proper shims for the blades in the blade grips last IRCHA.

Is this something new?

When the fly bar broke, did you check the main shaft bearings then?

If you want to try 710's you need to change the pinion on the clutch bell as well.

[ILoveRC]

Hey Chris, The vibrastions would come and go with as little as 50 main rotor rpm changes and as I would mix the fuel with different oil to fuel %
the very best resultls were obtained with a 35:1 mix and the low needle at 1&3/8 and the high at 1&1/2 The preformance of the engine seems to be smooth and powerful but the heli just vibrates so badly at certian head speeds that I have come to believe that The larger blades were were somehow causeing the vibration.So after replaceing the fly bar I flew it again and for a short while it was fine. Then the clutch began to slip and that is when I found the main shaft bearings bad. You could not move the main shaft it wasn't loose untill I took the engine out and loosened the main shaft and then it was clear the bearings were out. I wonder if the vibrations and main shaft bearings may have been what broke the flybar? could the main bearings have meet an early demise due to the weight of the heli hanging on them. Would it be wise to install a thrust bearing block? You should recieve the parts soon and you can look and tell me what you think. I am not in any way unhappy with the service, Support or any of the help you and your dad have given. You all are great, it is just that I have had so many problems that I wish they would just go away and let me fly my gasser in peace.After I get it back in the air this time I am going with a set of 720's to see if it will fly ok and Then I will go back to another brand of 800's to 810's because I do love the thought of those big boards moveing lots of air around I guess I would have to sum it up by saying that the heli is unpredictiabl about when and how bad it would shake
PS Thanks for all the help Sincerely Mike out in Arizona

[cbergen]

Some troubleshooting is needed here, to determine the cause of the vibes, which can and will cause other problems such as described.

If the vibes are not engine related, then they are either drive train, rotor head (including blades), or tail related (including tail blades).

Generally you can figure on where to start looking by the frequency of the vibes, by that meaning how fast or slow the vibes are occuring. Also, the indication of the vibes coming and going with different headspeeds would indicate something in the main rotor (including the blades).

Changing the fuel mixtures, which then changes the vibration frequencies would tend to indicate engine vibrations. Understand that with different atmospheric conditions (temp, altitude, pressure), slight and I do mean slight, changes to the needles may be necessary.

1 3/8 on the needles is NOT a panacea, depending on your conditions, you may need to run them slightly higher or lower. The constant here SHOULD be your fuel/oil mixture. Changing the amount of oil in your fuel will only make tuning that much harder.

If the problem is in the rotor system, changing blades would be a good starting point. Also the tracking plays a huge part in vibrations.

We demonstrated this at the Hirobo cup a couple weekends ago. My Turbine blades were slightly out of track causing some decidedly unhealthy vibes to show up in a hover, never mind going into a higher headspeed!

1/2 turn brought the blades in track, but still with a vibration in the heli. one more 1/2 turn still had the blades in track, but the vibes were now GONE. Totally gone from 1450 to 1650 in Idle up.

I remember we had to change the shims for your blades, due to the thought of them not having the same center, is it possible something similar is occuring now?

[ILoveRC]

Your memory serves you very well and with Gary Travis at the transmitter, at a specific rpm you could not see any vibration at all, smooth as silk. But it just woln't remain. So I will go back to the drawing board. This time with the new bearings and a whole new set of blades and gear ratios.
One more time Chris this is not your problem. It is ignorance that is causeing me problems. And I appreciate your input very much and the best to your Dad Sincerely Mike out in Arizona
"If you lthink education is expensive you aught to see the cost of Ignorance"