Crankshaft end play

[sctholson]

Hi All,

After a scary goblin gasser flight where it seemed I lost radio contact a few times and a test of the BD3sx rescue feature which sent the heli off on a path of about 45 horizontal to the ground I landed safely, fewww!!!

I use a Graupner radio and sent off my log file for review and I never lost radio control with the heli, and with the behavior of the BD3sx I'm thinking that I was just very high on vibration. I threw the skookum 720 on one of the servos, removed all the blades and ran it up to speed, over 40 up/down motion on that vibration chart, higher than the last time I checked it like that.

I knew I had some endplay in the VX300TT crankshaft and now I've pulled the engine to figure out how much and what to do about fixing it. I mounted the engine in a vise (grabbing it by the engine mount for the goblin) and set my dial indicator over the flywheel, zeroed the indicated and then lifted the crank... .014 end play. Is that a lot or a little?

What should it be? I noticed Dave's motors offers shims that are titled Zenoah crankshaft shims and I ordered some. Can anyone lend any insight to what I should aim for when I reassemble? Should I shim behind both bearings equally or just one of the bearings?

I haven't dissembled the engine yet as I'm waiting on the flywheel puller and piston stop (as well as the shims).

Thanks in advance,
Scott

[jc23cl]

Hey Scott,

I have all my Goblin Gassers (actually all my helis) fitted with BD/HC3SX and they are super smooth. I have stated before that HC3SX never worked well until I fitted a TRM motor, the rescue and all other BD functions work as well as any of my other electrics.

Track down the vibes and you will be Impressed how well this combo works, the Goblin is especially smooth given all the belt transmission points !

I understand this doesn't answer your question, but at least know that the bird and HC3SX should be rock solid, my TRM is also Incredibly smooth.

Good luck. Joey.

[sctholson]

Thanks Joey,
I know it will be as soon as I chase this down. Being winter here adds a complication in that all the foam mounting tape gets harder than a rock and its like a rigid mount under the BD and all the vibs transfer through.
I'll get to the bottom of it and it'll be good
Good to know of your experience, thanks.

[sctholson]

Yesterday I got the flywheel puller and piston stop (and also crankshaft shims). Took the engine apart and shimmed the crank so that the crank was still free spinning but no physical end play. Four shims did it at .003 each.

Engine is back together and I'm reinstalling in the heli this morning and will give it a run today.

[LoveToFly1]

sometimes the softer mounting tape is the problem. the BD likes to be hard mounted. not soft mounted. it utilizes internal dampening, and the metal case of the gyro (heavier and dense material) helps keep the frequency of the vibs out of the problem range.

[fastflyer20]

Checking the Zenoah manual, it calls for a max limit of .020" crankshaft end play.

I have tested a few iterations of the VX300, they have been smooth running. On the Goblins, the tail literally looks like an electric heli with the BD. Any other FBL I tried has the slightest twitch.

BD is very vibe tolerant, mine have had a light drift to the right when excess vibration was present. Other FBL units freak out under the vibes that were present (30.5 cc engines in Trex conversions). Mine have always been mounted with one layer of 3M gray outdoor tape. The BD hates to be bumped during boot up, is it possible it was bumped? What color was the light at take off? If everything else checks out, perhaps there is an issue with the BD.

[Toxic Al]

I wished you would have called me, i prefer there is some side play in my engines.

[sctholson]

Hi All,

No harm done at this point. I did run up the engine and noticed no real improvement with the reassembly as I had done. I did not see that the manual called for a max end play number. Wish I did see it as it would have saved me some time. After this run up, I looked elsewhere for some up down (vertical) play and I noticed that the first transmission gear on the upper assembly (the gear that engages the main gear had some up/down play so I've shimmed that too).
I've run the engine up, on a towel like all the others and the overall vib numbers I realized on the skookum is slightly better after fixing the transmission gear, so perhaps that was the issue all along.
I'll pull the engine and remove the shims, since that seems to be preferred.
I did a range test this afternoon and found I was well above the minimum for the radio.

Tom, regarding your questions, I'm pretty sure that it was not bumped when armed. No one was at the field with me, so I wasn't distracted. I always take the craft to where I'm going to take it off plug it in and wait. The color light was yellow.

Not sure how to diagnose the BD as to whether it could be the problem. I'm hoping to get a break in the weather to go out and test it again. We're looking at rain and wind here in Vermont over the next few days. Not conducive for flying.

Sorry I didn't call Al, guess I just wanted to tackle this engine thing on my own, or at least give it a try.

Thanks for the feedback guys, I'm trying to do my best.

It sounds like you guys are collectively suggesting to use grey tape vs any foam at all. so not even the foam tape the BD comes with?

Scott

[fastflyer20]

I had such good luck with the 3m, I never tried the stock tape.

On HF and RR, F1 Rocket - Danny is the guy for BD in the USA.

[LoveToFly1]

i have not had good luck with any of the stock BD tape on a gasser. on an electric, yes, but the gasser really needs 1 layer of the grey 3M tape. any more, and it can cause some weird issues.....

[sctholson]

Thanks all,

I'm replacing the foam tape with 3m VHB which I have and also suggested by Danny. I'll have that done and will try it again.

I've removed the shim in the crank and am ready to go.

I do notice my main gear has some backlash. Not sure if that could be causing vibration, I tend to doubt it, but I'm curious. Should their be any backlash in the main gear?

[LoveToFly1]

yes sir. you should have some backlash in your main gear. it will actually cause vibrations if you do not have enough. backwards, i know....

yes, that clear tape is good too. it is just harder to find for most. that grey tape i buy by the 3' roll at walmart.

[sctholson]

Originally Posted by fastflyer20

Checking the Zenoah manual, it calls for a max limit of .020" crankshaft end play.

I have tested a few iterations of the VX300, they have been smooth running. On the Goblins, the tail literally looks like an electric heli with the BD. Any other FBL I tried has the slightest twitch.

BD is very vibe tolerant, mine have had a light drift to the right when excess vibration was present. Other FBL units freak out under the vibes that were present (30.5 cc engines in Trex conversions). Mine have always been mounted with one layer of 3M gray outdoor tape. The BD hates to be bumped during boot up, is it possible it was bumped? What color was the light at take off? If everything else checks out, perhaps there is an issue with the BD.

I think I'm beginning to see how sensitive to bumping the BD is. I started it up the for the first time since the last dis-assembly and the engine started and ran fine, all the controls seemed to work fine on the ground, except for the rescue which pitched the swash backwards. I shut the engine off, powered everything down and then back up again and started the engine, this time the swash, when I hit rescue, did as it was supposed to and just increased collective evenly (no pitching back).

Lesson learned, test this on the ground prior to take off, at idle and see if operation is correct, if not, power down and restart the whole thing.

Looks there is a break in the weather and tomorrow I hope to get airborne.

Merry Christmas,
Scott

[rbort]

CR should work perfectly no issues with it, in older versions it used to go slightly back or forward in the air but its much better now.

I usually turn on my helicopter once its on the ground at the takeoff spot, wait for the servos to come alive and start it. I don't think a little bump will hurt it or carrying it to the runway started will bother it either. If you bump it too much it doesn't initialize and gives a flashing red light, I do that on purpose sometimes (roll it left to right on powerup) when I want to check the throttle servo only and don't need the other servos functional, could be because I'm doing something on the bench or the blades are folded back in the holder and I don't want to take them out to do this.

-=>Raja.

[KSHeli]

I seem to always.power up the electronics on the end gate of my pickup and then carry it to where I will take off and have never had a problem with CR not going straight up, with the exception of forward momentum. I really don't worry about the 30* tilt or whatever they say it is, I just grab it and walk. It's all good.

[LoveToFly1]

also, you can get the heli into a stable level hover, do 3-4 pirouettes and CR seems to re-set its level....

[sctholson]

Okay then, Update:
1. Took out some of the shim in the crank
2. Inserted shim in the pinion gear to eliminate that up down gap
3. Replaced thick tape with 3m clear under the DB

Flew the other day, no odd tendencies, no loss of control. Sport flying and hitting rescue worked perfectly, the moment I did one tick toc and then tried the rescue it didn't work right. Okay then... don't do any tick tocs. Landed refueled and flew around... damn... muffler cracked in half in flight. It was an RJX and had been through a few crashes and just chose this moment to give up.

Scouted a stock muffler and went flying the next day. Three full (7 minute) flights and as the timer went off on the last flight I was headed toward myself nose in and went to rotate toward tail in and the tail didn't respond, a moment later it responded. Whew! Landed.

I've reported my findings to Danny. Not going to fly this Demon. I don't trust it. So I'm grounded at the moment. Considering the vibration tolerant, but gets freaked out with a single tick toc and I lose temporary control... it's not a good sign.

Danny has asked for my contact information. I don't know what that means exactly, but I expect to send it in for service or something like that.

Thanks for all your thoughts and suggestions.
Scott

[sctholson]

For those interested in closure on my scenario, I received a replacement 3sx from Danny and he informed me that my unit, was technically fine, although it was an older version that did not have the dampening of the current production versions.

Today, I took a little time away from work (got to have the right priorities in life) as the weather was as good as it gets here in Vermont 31 degrees 3mph breeze and partially sunny and put four flights on the new 3sx.

The thing flew flawlessly and I am building some confidence with it.

So thanks again to Danny and everyone else who has provided feedback over the last few months.
Scott

[LoveToFly1]

great news!