EXTRA Torque Tube Bearing Holder(s) for T-Rex 500 ?

[tony#1]

Re: EXTRA Torque Tube Bearing Holders for T-Rex 500 ?
I read this suggested modification some time ago but cannot find the details.
Can anyone help please?
The idea was to make the torque tube assembly more rigid. I am not sure if one or two additional bearing holders should be used and also what the positions should be in the torque tube.
Any comments gratefully received. I am about to start my first proper heli kit build

Just as an aside the Align part numbering system has me beaten.

The Instruction Manual for the T-Rex 500 ESP for the part number 112 Torque Tube Bearing Holder is 500T047 with diameter of 14.0mm. Part 500T047 is not recognised by an internet search.
The additional bearing holders that I bought at the time of reading about the modification suggested using H50098T which has a diameter of 14.5mm. I guess the extra 0.5mm will not be a problem should I go ahead with the modification but the variation in part numbers is bewildering.

Thanks for taking the time to read this posting.
Tony

[Abenn]

The part number given in your manual certainly doesn't seem to match the usual Align numbering system.

Given that the 14.0/14.5mm dimension is the outside of a rubber ring with ribs on it, it doubt that the 0.5mm difference is going to be an issue.

I haven't done it myself, but I remember reading about people using two bearings in the torque tube, and that it's best if they're roughly, but not exactly, at 1/3 and 2/3 distance down the tube.

[Ignatjev]

If your torque tube is straight then there`s no need for this. On my beater 500 I`m using Gartt TT and there had to put even three bearings to get rid of vibrations.

[tony#1]

Thanks for the replies. I did a search of HeliFreak and found some postings on the subject from several years ago. Being a "belt and braces" (belt and suspenders") type of person I shall use more than one Bearing Holder.

[zzyzx_cm]

i would put one at the recommended spot regardless of how many i used.

[Abenn]

Originally Posted by zzyzx_cm

i would put one at the recommended spot regardless of how many i used.

Then you would need three bearings in total for, if you have one at the original spot (about half way down the TT) and then put only one other in at, say, about quarter way from the tail, you'll still have a half-length of unsupported shaft at the front end.

The idea of extra bearings is to reduce the unsupported length of shaft, so two bearings at about the 1/3 and 2/3 points achieves that. Three bearings at about 1/4, 1/2, and 3/4 points reduces the unsupported lengths even further.

[zzyzx_cm]

i wouldnt bother with it unless there was an extra sitting there as i was building it. this is pretty much snake oil. flies basically the same with with one. vib analysis and telemetry agree. i fly it pretty hard if that matters.