justhovering

Greetings to you all heli experts:

Question one: Is a brand new main rotor shaft true 100 %(no wobble) from lower bearing end to the rotor head end? Any heli basically.

Question two: What should be an acceptable wobble in thousandths of an inch form lower bearing to the rotor head?

For example if one end of the shaft is placed in a lath chuck and the other end is measured with a dial gauge, what should be the max

variance that these helies could tolerate?

Thank you one and all

matty_p80

hey JH!

i'd check any shaft before i fit it (justin), if there is any wobble the key is not to fit it! if it is new, try taking/sending it back to where it it was purchased!!

even the minutist variance from straight will have a detrimental effect which will get worse sooner! the speed the heads are turning at, it is not worth the sake of a few bucks to skimp on something that is not straight! you'll also find that you will wear the bearings out quicker (just like any rotating thing!)

hope this helps (i haven't measured any of mine in that detail so i can't give you any figures)

Matty )}}}}}]@>

justhovering

Thanks matty, I do appreciate your input on this subject.

Happy Landings

justhovering

Rafael23cc

My Feedback: (6)

I have read on books and articles that 0.002 inch is the maximum acceptable for rotating shafts. Now the problem is measuring that in a helicopter frame.

Rafael

FILE IFR

Steel shafts are almost never 'bent' when new, so you should be fine.

If you want to check a shaft just roll it on a supported piece of glass and look for spaces at the points of contact as it rolls.

BTW- People interpret a wobbling heli must have a "bent" shaft... Not always the case. An unbalanced main blade set, mis-aligned flybar, a slightly longer feathering shaft causing the feather shaft to slide laterally (Trim it OR use shims if need be), unbalanced paddles, main blades TOO tight in the grips (keep them loose to pivot freely) or a rotor mast hub not properly seated WILL GIVE THE ILLUSION of a bent main shaft.

Avoid chucking a shaft into a lathe or drill, some chucks will scratch a shaft.

BarracudaHockey

My Feedback: (11)

Roll it on glass and listen for a tap tap tap, if it does it then don't use it, if it doesn't, go for it.

justhovering

Thank you all for your input. Rolling the shaft on glass makes sense. Live and learn. Thank Heavens for these forums.

Thanks again

justhovering

Aframomum

My Feedback: (10)

After any crash I do the glass rolling thing with both the main shaft and feathering shaft to see if they need replacement.

Mark

dennisef

I have also posted questions on the bent shaft problem on the Blade copters. (Blade and Pro) I have been able to straighten them on a cast iron saw table by gently tapping them with a hammer. I backlight the sawtable so the imperfections will show while rolling the shaft along the edge. The blade helis have the main gear swaged on to the shaft so the glass rolling doesn't work to well. I also check them by using a tool shaped like a screw driver that has a hollow shaft. It is the same diameter as those shafts. If I put the shaft in the tool and it spins freely, it is straight. When it does not spin freely it needs work.
I have attempted to use a press like I use to straighten the shaft on the AXE but that does not work as well on the Blade shafts. On either one, you need to make sure to deburr around the holes in the shaft.
Would it work to take a small block of mild steel and drill hole in the solid block and push and almost bent shaft in to it? Would it straighten or just bind up? How about having a small steel block say 2x6x3/4 to sandwich the shaft between the block and the cast iron table? Roll the block over the shaft on the table, back and forth. Would that straighten the shaft?

BarracudaHockey

My Feedback: (11)

No need to be complicated.

Drill a hole in a 2x4
Chuck the shaft in a drill.
Put the shaft into the hole with a slight to mild side pressure on the hole and spin the shaft. It will come out pefectly straight.

wangchi

do it as it what it is from factory!~