Whiplash Gas shear issues

[raptor90se]

Hi all,

I make this post because with somes guys in France we had shear issues on differents Whiplash Gas.

The first time it's appear it was on the 0081 screw. All the four screws sheared one after one.
The second time was the 131-69-1 tail linkage rod.
The third was the 128-146
And the forth, the 131-62 the boom.

We all have the same motor setup. An OBR 30.5cc 8.2hp. We turned between 1750, 1950 and 2050rpm. The problem appear between 1750 and 1950rpm.


Do you know other issues similar to us?
Is there something to do?

Kind regards,

Joël

[fastflyer20]

I have not heard of any Whip gasser having this problem.

Unfortunately this appears to be caused by the 30.5cc engine, the vibration is too severe. I stopped running them in my heli's.

From my testing, I prefer a 270 (25.4cc) or 27.2 (270 with a 2mm stroker crank).

[raptor90se]

Hi Fastflyer,

Why do you think it's come from vibrations?
Whitch OBR did you get. Our motor is based on the 8.2hp full reed case. They have an heli tuning. I didn't found a lot of vibrations. but in case of vibrations, is it possible it can broke the boom and the other parts?

Cordialement,
Joël

[fastflyer20]

A friend and I built 28.5cc, 29.5cc and 30.5cc based on the 290 engines.
The 30.5 was in a HB700 conversion, I broke boom supports killed servos, slipped clutches, OWB and sheared bolts. The power pulse and the balance factor is not good for helis. Once I started to use 270 based engines, the structural problems disappeared.

This is why you do not see a 30.5 heli engine offered by Toxic or Hanson.

I did love the power, but could not afford the repairs to keep the heli running

[carey shurley]

when a motor is hammering the airframe, it tends to show up in the tail boom because it has such a long moment and the fact that it broke right at the clamp implies the t/r is probably moving around.

Assuming you've checked for bent shafts, bearing issues, etc its likely motor vibration. Whether its a problem across the board or just at specific RPMs is impossible to surmise without careful study

you might TRY using a graphite tail boom, if its vibrating this will expose it more obviously and it is less likely to crack.

[rbort]

Who makes it, how well is it modified? That has alot to do with it. I know some people modified 30cc engines and they can be much more vibrant. Hanson makes a 29cc motor that works quite well, I know a guy that has been using them in his whiplash and Spectra for a couple of years. I use the 270 motor (25.4cc) from Hanson like fastflyer, those motors do really well and I got 433 flights on mine now still with the original tailboom that came with the heli a year ago.

-=>Raja.

[Rudy]

I have never broken the boom like that, but I have sheared off the bolt that holds the boom support to the bracket a couple times. Each time it was due to the wah, wah's, the tail shaking bad. In my case the wah wahs where caused by a couple of problems, gyro gain to low, slop in the tail drive (allen loose in the tail gears, bolts in torque tube end loose) and issues with the clutch and sprag.

It all comes down to keeping the tail steady.

[fastflyer20]

A solution:

Ask OBR to modify 270 cylinders and pistons for 27.2cc. You can then still use the 2mm stroker crank and reed crankcase so the cost would not be too bad.

[raptor90se]

Hi all for your answers,

Raja, the motor was modified by O'NEILL Brother.
I will asked them for a modified 270 to put on the reed case.

The guy witch broked his boom told me he try yesterday to fly at above 1900 rpm and the vibrations seem's to be less.
I will try to fly 2200 rpm next weekend. I will tell you the results.

Cordialement,
Joël

[raptor90se]

Rudy,

Sorry but what is the "wah, wah's".
Did you often broke parts du to Shear?

Cordialement,
Joël