Mini tail blow

[learnedthehardway]

Had a spare airframe I decided to get airborne that is flying perfectly except for some serious tail blowouts under heavy load.

Never had any problems with my other Mini's tail accept once when the tail pitch control rod was broke and I didn't know it and one other time when I managed to shear the pin that attaches the pulley to the tail shaft.

Only difference is my original Mini came with a full Lynx tail assembly and Mini #2 has the stock tail. Both have the Lynx solid pinion and lowered fbl hub.

Checked all the mechanics and there's no slop, can't get the tail pulley or hub to slip on the shaft or get the belt to slip on the bench even applying a lot of force. Plus the tail control rod isn't damaged. Left my other Mini at a friend's house who is out of town so I can't compare but the only thing I noticed is the control rod feels hollow and flimsy compared to how I remember the one on Mini#1 feeling.

Long story short, has anyone had trouble with the stock tail ratio?? All I've used so far is the Lynx.

Rigged up a tail rod guide from another heli in case the rod that's on there is flexing under load, getting ready to go test that in a little bit. Other than that my main suspect is the belt since the teeth look worn but I can't get it to slip on the pinion, main pulley or tail pulley on the bench putting alot more pressure on it than I usually use to test belt tightness.

Anyone else run into this??

Running a MKS ds95i so I know the tail servo is up to the task.

(Edit) Just realized I did the solid pinion mod yesterday and didn't wait long enough for the Loctite to cure properly so the pinion may be slipping on the shaft.

Sure I can figure it out so I guess my main question is on the stock tail ratio. If it's not known to cause blowouts then I'll know the issue lies elsewhere, if it is known to blow I'll change the tail pulley.

Thanks

[jrman83]

My tail is completely stock and my control rod is not super stiff, typical hollow cf rod. No issue with blowouts at all. I have the same tail servo.

I had an issue with the solid pinion slipping on the main shaft - twice. Motor doesn't come with a notched area, so I made one. No more slip. Or, not yet anyway.

[learnedthehardway]

Originally Posted by jrman83

My tail is completely stock and my control rod is not super stiff, typical hollow cf rod. No issue with blowouts at all. I have the same tail servo.

I had an issue with the solid pinion slipping on the main shaft - twice. Motor doesn't come with a notched area, so I made one. No more slip. Or, not yet anyway.

Thanks for the info Ben.

Mattbeau who I got my 1st Mini from really has his stuff together and must have added a flat spot on the shaft unless it was the owner before him.

Noticed the shaft on the second Mini doesn't and was wondering if it was a older shaft or whatever cause the flat on my other shaft looks like it was done at the factory. Usually easy to spot a Dremeled flat spot...lol

Wish I thought of that last night especially since it's a no brainer to let the loctite cure now I have to wait at least 6 more hrs to test it

Hit it with a good shot of red loctite and if that doesn't work I'll grab my Dremel from work and add a flat spot.

Thanks bro.

[Mikej]

I would ensure that it has the flat spot rather than glueing it on with Loctite (never tried that) - however I have had other pinions slip if they didn't have a flat-spot to grip onto.

The other areas that I would check are that you have full movement both ways on the tail slider and that the tail pitch lever arm is moving feely within the grooved disk - it has been known for these to bind / bend rather than moving freely

[learnedthehardway]

Thanks for the tips.

I would have just put a flat spot on it if I didn't leave my Dremel at work. I've had excellent luck with red loctite on smooth shafts using pinions with only one grub screw and the Lynx pinion has two.

Put a little dab in the center hole on the bottom of the pinion so it gets spread up through the center and on the shaft as you slide the pinion on the shaft, then do the grub screws how you normally would. Thought about putting a spec of 609 on there but it takes a dangerous amount of heat to get stuff to let go.

Have a older Align 3-4s motor with a smooth shaft and owned a number of rc car/truck motors with smooth shafts and never had any slipping issues using that method with red loctite. Only prob is it can be a bitch to get them off but some heat takes care of that.


Have had pinions slip on motors with flat spots but that's cause I only use blue loctite on those.

Those were older motors so it may slip on the powerful 6s Scorpion but I doubt it since it didn't slip on my Walkera or heavy ass Trex running a low kv but high torque motor.

If it breaks loose I'll go with a flat spot since once broke loose it will come off easy...lol

Thanks for the input. I'll double check the slider and bellcrank.

[learnedthehardway]

Might have found it. Issue persisted so I thought the loctite let go on the pinion but when I went to take it off it became apparent real quick that it's still practically welded in place.

Noticed the screws that hold the shaft to the motor housing were loose and the shaft rode up so the one flat spot was no longer aligned with the set screw. Pressed it back in place and reinstalled the screws with loctite so hopefully that gets it.

Never had that happen before. Going to test it out but think I'm going to tear this Mini down and rebuild it. Found a couple loose screws, couple missing screws and now this.

Got lazy since the last two used helis I bought, Mini#1 and a P500 stretch were in perfect condition and build very very well. Still should have known better cause everytime I get lazy and cut corners it bites me in the ass.

Pretty dead in here these days but I'll post an update whether that was the problem or not and any other issues/potential issues I run into other than being lazy and stupid in case someone runs into a similar issue someday.

Thanks again for the info and tips Mike and Ben, much appreciated.

[Mikej]

Glad you found the problem - mow that you mention it I have heard of that before once .

Agree that it's a shame that it is so quiet in here - I still use my M-P as my daily flyer (hence my thread about support / parts from MSH - I really hope that MSH continue to support it)

[learnedthehardway]

Originally Posted by Mikej

Glad you found the problem - mow that you mention it I have heard of that before once .

Agree that it's a shame that it is so quiet in here - I still use my M-P as my daily flyer (hence my thread about support / parts from MSH - I really hope that MSH continue to support it)

Sure is a shame, surprising too since the 450x forum still has a fair amount of traffic and it's a POS compared to the Mini P.

I bought this 2nd Mini for parts and to rob the electronics to get my Chase back in the air which lasted all of 5 flights. Hate working on the Chase plus it's a finicky lil bitch and think the Mini flies better anyway, so robbed the electronics back and Mini#2 was born.

[jrman83]

Glad you found your problem.

[learnedthehardway]

Tested it out last night and another quick test this morning, looks like that was it.

Was wondering what the hell was going on since the mechanics looked fine and I never had any issues with my other Mini after an initial strip down/rebuild and two crash rebuilds.

It's on now!! Finally stays light out late enough for me to sneak some flying in after work Too bad the Gens Ace packs I have are already getting tired even though they're 1/3 as old and have seen 1/4 of the use/abuse as many of the Glaciers I have. Time to order more lipos

Thanks again guys.

[learnedthehardway]

OMFG

Assumed the second airframe was a stretch since it came with the 1300kv 6s motor and 360mm blades plus a bunch of cheap 325mm blades. Didn't pay much attention just plugged the esc into a spare fbl to make sure the servos worked and the motor spun then stripped everything cept the motor to put in the Chase and put the airframe with my Mini spares.

Didn't like the Chase and left my other Mini at a friend's house but he's out of town so I slapped everything back into this airframe.

Flying good now but noticed I had to run tail gain a little higher than my other one. Didn't think much of it.

Teeth on the belt look pretty worn so I decided to install a new one last night. Get it together and notice that the stretch belt I put in is too long. Checked the package and it says stretch belt mini, ok wtf??

It has the standard length boom on it and I ran 360mm blades for a few flights!!!!!!!!
Holy shit that may be a new record in heli stupidity for me. Can't believe I did that, didn't even notice without my other Mini here for comparison. Oh well, guess I can run the longer tail blades I have on the stretch with 360's without worry since I ran standard tail blades with 360's and a short boom.

Can't help but laugh and can't believe the main and tail blades didn't collide when I was doing flips, rolls forward and backward loops and diagonal flips.

Once you been around a little while and feel like you know your stuff fairly well I guess it's easy to become a little cocky and miss simple stuff that should clear as day.

Being lazy will get you every time but boy did I get lucky on that one. Instead of the usual teardown all I did was check for loose/missing screws and give everything a spin or tug to check it.

Good thing I decided to use 325's after the first couple/few test flights in case anything went wrong since I only have 1 set of 360 blades left that I really like.

Too funny and stupid even for me

[jrman83]

Glad it didn't turn out worse or there would be some angry posting going on

Was the blade length for a standard 325? I run 353 on my stretch.

[learnedthehardway]

Yes 325 for the standard Mini. Use RJX 360's on my stretch, lighter than Zeal 350mm.

Have also used Align 360 and Zeal 360mm and 350mm. Thought about trying the Switch 353mm but the Switch blades I tried on the P500 made the flip rate excruciatingly slow but that's because they weren't the XF or whatever the ones designated for 3d are called.

423 Switch on the P500 were the best sport but worst 3d blades I ever used although on a 450 they might have been great. Slowing the flip rate on a 500 where it already felt slower than what I'm used to made them intolerable.

[Mikej]

I'll say it quietly, but I've had really good success with the ALIGN 325, 360 and 425 blades on my M-P, M-P stretch and Protos. The smaller blades particularly are really quiet which is handy as I fly in a public field and it sounds much less intimidating for others.

[jrman83]

The 353s work well for me for now. I still have a spare set so I will use them up before I make a switch to something else. I have a few sets of Zeal 360s that I have as spare for my 360cfx. At least I will get use of them I guess once I sell the 360.

[learnedthehardway]

Have some 325 Align 3g blades and they're great, even survived 2 crashes on my 450 Trex, not hard crashes but not soft either. Perfectly balanced and nice flying.

Second mini came with some of the blue Align 360's but I haven't flown them cause it took a mountain of tape to balance them. Suspect they may have been from two different sets since they were more imbalanced than cheapo Ebay blades usually are.

Zeal blades fly great but every set I've used from 325-425 required some balancing or they'll make the main bearings chirp. No biggie except the 425's had an incurable imbalance that made the main bearings on my P500 chirp like a flock of birds despite weight and cog matching perfectly with one piece of tape. Only blades I've ever owned that I couldn't get to run silent. Flew great and didn't vibe but the chirping drove me insane. All I can think of is something inside was shifting during rotation throwing off balance.

My favorites so far are the RJX Energy 360's on the Mini and SAB 465mm on the Protos stretch. Both were perfectly balanced plus provide good pop and agility. Only ones I've used of each brand so I don't know if I just got lucky or if they all come perfectly balanced.

Might give the Switch 353mm a try since everyone seems to like them. Love the 60mm Switch tail blades and like the look of Switch blades plus they're always perfectly balanced.