Landing Strut Bolt Problem

[malc1]

What's going with the M4 landing strut bolts?

Three sessions out with the Whiplash Nitro and have come back with a bolt sheared off in a cross support every time.

Not even heavy landings and no struts broken.

It means that I keep scrapping the M4 threaded supports at a time when parts are short.

Anyone else have this problem?

[tonyd12]

Common that's one of the reasons to convert to Tuf struts.

[OldGasser]

Originally Posted by malc1

What's going with the M4 landing strut bolts?

Three sessions out with the Whiplash Nitro and have come back with a bolt sheared off in a cross support every time.

Not even heavy landings and no struts broken.

It means that I keep scrapping the M4 threaded supports at a time when parts are short.

Anyone else have this problem?

Hi malc1,

The struts act like a lever on the M4 socket bolt and pulling it out of the 133-135 landing-gear frame post. Considering the length of the landing strut vs. the short distance between the M4 bolt and the upper edge of the strut above, this lever is quite strong. It also puts quite some pressure on the frame which is probably the reason for the frame-doublers.

An other strut between the left and the right landing-strut would would brace the struts together and take the pressure off the M4 bolt and the frame. Requires some tinkering.

As tonyd12 said, converting to turf struts is probably best and easiest.

Kind regards
George

[malc1]

I have just managed to order a white Tuff Strut conversion set even though I have several spares still in my tool box.
A bit of a pain to keep replacing these parts but may still use them for a bit longer until I run out - as long as I don't break a frame.

Tuff Strut ordered in case I can't find one anywhere later - to use at my leisure.

[jdwelch]

I had the same issue some time back with my Whiplash nitro. Broke at least three strut bolts for no apparent reason. Fortunately Chris Lund at MA helped me solve the problem. He deduced it was caused by vibration, not over tightening or hard landings. Helped me balance the clutch/fan assembly and the issue went away. Never happened again. Was also aggravated by a rough running OS105 HZ-R with a bad regulator at the same time but even after the engine fix it continued to happen. To protect the frame I eventually went the the Tuff Strut conversion. Very effective solution to broken strut issues as well.

[malc1]

Funny you should mention vibration.

I'm trying to set up a YS120 in the helicopter using a Silver line V Bar and have a bit of a tail wag problem and am seeing all sorts of vibration reports in the flight log.

I have tried different plugs including Enya5,YS no2 and OS 8 and am currently trying a OS 7 out and have had mixture settings up and down the scale.

I balanced the fan and hub when the helicopter was put together so this should be OK so am thinking that the motor is not quite running right yet.

You could be right here though as before breaking bolts off I had an issue with losing a couple in flight where they backed them self out.
This was with thread lock.

I have thought about getting an OS 105 to try instead of the YS.

[OldGasser]

Hi malc1,

Thread locked bolts backing themselves out? Sounds like really horrible vibs.
Wonder how long the electronics and the mechanic will hold up this way.

Have you tried the vibration-analysis-feature of the vstabi to track down the source of the vibs?
http://www.vstabi.info/en/node/385
http://www.vstabi.info/en/sensor_mounting

For the vibration analysis the pro-version is needed
http://www.vstabi.info/en/v5_full
May be worth the 35 Euros, it also has the governor.

If you do not have a bluetooth-modul and run it on the bench without blades be very careful with the USB-cable. Guess how I happen know this?

Kind regards
George

[malc1]

Already running the Pro version of the V Bar software and have been checking the logs when I have come back from the flying field.

Attached are the last two with the only difference being a different glow plug being used.

An Enya 5 on the first and OS8 on the second one.

Both these flights ended up with broken bolts.

I have already posted these logs over on the V Bar forum and have got to get the bluetooth adaptor to check the live analysis set up and also send them over a pic of the sensor mounting.The second log is a continuation from the first from page 11 onwards I think.

[OldGasser]

Hi malc1,

Wow, the logs look bad. Assuming the vibration warnings do not come from hard 3D maneuvers it seems to me you get the extreme vibs when you try too rev the engine up. Can you actually fly this way?

I do not think its the sensor mouting. Since bolts get broken and back out there must be something causing really heavy vibs.

The frequency of the vibs in the live-analysis can give a clue where to look. Can you post a snapshot?

Alternatively you just can try the remove the tail-blades, spool the engine up on the ground and see, if the vibs go away. If not remove the tail-blade-holders,... remove the whole tail,... remove main-blades (be careful not to over-rev the engine), rotor-head,...
You take away one piece after the other and see where the vibrating stops.

Kind regards
George

P.S. Just thinking:
I once had a tailwag-problem too, almost drove me insane. Searching back and forth, checking all the standard-stuff everything seemend ok. Yet the tail kept wagging and vibrating. After days and days I found, that the tailblades were out of track by a little.
Your heli was preowned, maybe the tail-pitch-yoke is bent or the blade holders? Screws of different sizes used on the tailhub?

[jdwelch]

I have no experience with the YS, but I did find the OS105 much easier to tune and get to run smoothly when I changed from Cool Power 15% heli to Cool Power YS 20%. Runs stronger and very much easier to tune.

[malc1]

No hard 3D with these logs - this is just hovering with a tail wag,not a stable hover either.

Yes I bought this Whiplash pre-owned and have yet to fly it properly.

I have changed the Main shaft, tail shaft,Boom and torque tube before these test flights.

[jdwelch]

One other point to check is the main gear to jack shaft gear mesh. After landing, make sure the blades will rotate by hand with no binding. The main gear can heat up enough in flight to bind at its widest point in rotation. I had to drill out the holes in the frame so I could slide the front transmission with the jack shaft back ever so slightly. Cured much of my vibration problems. Following this discovery, Chris changed the frame hole size slightly on follow up production. I was really fortunate to have Chris's help through these problems.

[malc1]

Hmmmm.... pretty unlucky for me at this time that MA are no longer about to offer any direct support if I should need it with any issues.
And random swapping out of loads of parts could be a problem.

I will get the V Bar blue tooth set up and have a look to see if this helps me out a bit.

[jdwelch]

If you have any specific questions I can ask Chris Lund. He is the designer, along with Bobby Watts, and actually did the production CNC and milling work. I see Chris regularly as we are both members of same flying club. The jack shaft gear clearance issue is easy to diagnose and fix if it is present. You can look at the front transmission mount points to determine which holes need to be slightly enlarged to allow the small adjustment needed. Hang on to any parts you have replaced for sure. If you have seen no changes in vibration, they are probably fine. The parts you listed have been relatively trouble free. I lawn darted my Whippy into the MA warehouse roof and didn't bend the main shaft or tail output shaft.

[malc1]

OK thanks for the info.
I'll see how I get on Saturday when I next go down the flying field.

[malc1]

Nope, no further testing with this yet.

Luckily spotted a servo playing up yesterday while testing.
Possible due to the vibes?
No spares available in the UK so grounded while I sort it out.

From a post on the JR section.

[ame]http://youtu.be/FoUA9mbRx9U[/ame]
[ame]http://youtu.be/ECYGDxa4ajQ[/ame]

A faulty coreless motor by the looks of it.

[OldGasser]

Hi malc1,

Randomly swapping parts would indeed be a problem. You would end up building and rebuilding the heli back and forth, not to mention the cost. Basically you would buy almost an other heli.

Thankfully there is no need to do it randomly, you can locate the problem systematically:

Remove the whole tailassembly, run the engine.
a) If vibs stop, the problem is with the tail.
->inspect the tail closer:
- Remove tail blades, run the engine, see if vibs stop. If yes -> its the blades.
- If no, remove the tail rotor hub wth the bladholders. Vibs stop? yes -> its the hub/blade-holders.
And so on, remove the tail-shaft,... remove the torque tube,...
b) Otherwise the problem must be with the mainrotor, gear mesh or the engine.
So do the same with the main-rotor: Blades,.... rotorhead,.....

The vibration analysis of the vstabi can help you too. The frequency of the vibration
tells you the rpm.
For example If you run your engine at approx 12000 rpm it would yield you a frequency of 200 HZ = 12000 rpm or 400 Hz = 24000 rpm. The engine changes direction twice per rotation.
If the rpms indicatet are about the headspeed you are runing, it is likley the main-rotor, mainshaft or the maingear. Same with the tail.

After knowing the frequency/rpm that you isolate the problem by removing the parts as above and find the bad one.

Kind regards
George

[OldGasser]

Hi malc,

Your tail-servo? This would explain the tail-wagging.
Is the servo faulty because of the vibrations or did it cause the vibrations?

Kind regards
George

[malc1]

Good question that George.
This is the cyclic here that is faulty for starters.

I now have a new Cyclic servo and DS8900G tail servo coming and the blue tooth unit has been set up.
I'll replace both of these servo's and see what happens.

[OldGasser]

Let us know. Good luck.