stuffing tube EXPLOSION

[kevinpratt823]

Did you have a sufficient gap between the drive dog and the strut to allow the shaft to shorten when it tightens up under load?

[sundog]

You can see that the motor is at one angle, and the flex is another - causing a bend at the support area. That will build up a lot of heat fast. Adjust your motor to be at the same incline as your flex or it may happen again.

[Ken Haines]

Stuffing Tubes

A couple of questions...
Your set-up Kv / cell count ie; what RPM ?

I would suggest if you exceed 40,000.
or set-up a bigger higher amp boat
you may want to ditch the teflon.
Otherwise the teflon is fine.
Increasing the shaft diameter does help.
The .187 shafts as previously suggested are great.
Odd thing, but an S-bend actually gives you
a smoother cooler stuffing tube due to less vibration.
That may be hard to believe but is definetely true.
A very slight bend is where I have had most of my
troubles....actually on a Q-Mono. Tried everything,
Then Paul Pachmeyer suggested an outer stuffing tube
of stainless tubing, this fits right over the brass, just
1 additional ID. It has worked perfect and after blowing
that stuffing tube no less that 5 times at various nationals
it has never been a problem since. I have also added a zerk
fitted aluminum block so that it makes it easier to grease
every single heat.
Hope one of these ideas help,
Ken

[martin]

Deff looks like in the pic theirs something strange going on re the angle of the motor/couping is at & the angle the stuffing tube has.

[lv_reefer]

Ok my support was a 3d printed support and the flex shaft went straight into the collet (no deflection at all). The pic made it look like things were not aligned because the flex is wrapped around the short piece of stuffing tube and it is cocked at an angle but they were aligned very well. There is one bend in the stuffing tube and it starts 1" (25.4mm martin this is for you ;-)) out side the hull and it is 3" long, nice and easy. The setup is a DF 22 3655 1850kv on 6s = 41,070rpm ~85%~ 34910rpm turning a 3517 cnc prop with ALL UL1hardware.

[martin]

A .130" flex on a 36mm size motor is to small in my opinion even more so on 6s at those rpm.

[lv_reefer]

I guess inexperienced... I have never seen a flex shaft shread like this lots of other stuff but never a flex give out. I was trying to keep the rotating mass down to a min i.e. the cnc prop...

[martin]

I have a few times, the problem is the damage that is caused after it breaks. This is one of the reasons some prefer not to run teflon liners as it grabs the broken flex & makes things worse, it can also be that some times the teflon causes flex failures ecspesially at those revs where the teflon melts & grabs the flex causing failures.

[lv_reefer]

HUH!!! Never even considered.