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E-flite . Next D . Fast Lad Performance

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Thunder Tiger Raptors 30-90 - Imperio > Exploding tail on your raptors.
 
 
Barney
Key Veteran
Location: Inverness Scotland

Flying Tivo

My R50 V2 manual gives the size as 3x8x4...Just found out AFTER I ordered them from Revolution models here in the UK

Your the second person to give me this larger size..you sure they are 5x10x5 before I re-order

That makes things a whole lot easier if they are available of the shelf..I was getting ready to do some modifying

The ones I have here from Robbe have a larger hole one side as per main blade thrust brgs..is there a right way round to fit them + do I fit the thrust brg to the outer side...

cheers
06-08-2006 Over year old.
 
 
Yug
rrProfessor
Location: UK. Herts

Barney - in my left hand I have a V2 tail grip bearing. In my right hand, a digital vernier calliper.
Inside diameter = 4.99mm
Outside diameter = 9.99mm
Width = 3.98mm

ie 5 x 10 x 4
06-08-2006 Over year old.
 
 
Barney
Key Veteran
Location: Inverness Scotland

Thanks Guy..just what I needed to know..bit of grovelling required to Rev models then.. then order the right size.. (another day lost..I.m really cut up bout it..might have to fly my Dyna instead)


I'M SURE they are going to believe the manual is wrong LOL..but it's true..

Flying tivo pointed out you can get a thrust brg of the shelf that size too..save me doing all the modding..have to decide in what order I stick it all together though..likely one side of the thrust will be a little larger too ..as per the main blade grips

BTW I'll post a picture of the mast collar for the lower brg when it arrives..gone missing in the post..twas sent out on 2nd..looks like it will be next week now for it though

thanks
06-08-2006 Over year old.
 
 
Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

There is two links in the prior post, one in england and the other in the usa. Yes they are 5x10x4mm, and fit them on the furthes place form the tail rotor shaft.

Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
06-08-2006 Over year old.
HOMEPAGE  
 
 
Yug
rrProfessor
Location: UK. Herts

If you go to www.modelfixings.co.uk they have some grooved thrust bearings the correct size.
06-08-2006 Over year old.
 
 
Barney
Key Veteran
Location: Inverness Scotland

Thanks Felipe/Guy parts on there way

brian
06-08-2006 Over year old.
 
 
Barney
Key Veteran
Location: Inverness Scotland

Hi Felipe/Guy

I have a couple of 5x10x4 std brgs & 2 of 5x10x4 thrust brgs (with tracks)

Ideally as pointed out the thrust brg goes to the outside, std brg to the inner..

I should have ordered the 5x10x3 so I could fit a 1mm washer between the brgs..to late now

I have also checked out a few model manuals and notice the Sceadu Evo appears to have the thrust brg on the inner side???

A couple of older 30 size helis only used a thrust brg whilst others are similiar to the raptor having two ballraces..the big ships mostly use combinations

If I use the brgs I have above.. with the thrust brg to the outside the centerfugal forces will cause the brgs to bind as there is no washer between them..

Its not ideal I know but, if you fit the thrust brg to the inside with the small hole end towards the outer brg the forces will work in my favour by pulling the inner race of the outer brg into contact with the thrust brg when under load..(note..Also the thrust brg small hole end must be fitted towards the outer brg as it has a smaller outside dia and that will allow it to rotate within the grip)

I am pretty sure it will work ok.

I have assembled it both ways round and done a pull test (I realise it's nothing like the real forces) and it seems to have enough movement to work..under compression you can feel the friction but whist pulling it all seems smooth

What you reckon?
06-09-2006 Over year old.
 
 
Yug
rrProfessor
Location: UK. Herts

Barney - I calculated the forces for you.................

mass of blade + grip =0.013Kg
radius from shaft centre to CG of blade + grip = 0.04m
rpm=9000
v=38m/s at CG
F=m.v.v/r = 0.013 x 38 x 38 / 0.04 = 469N = 105Lb

ie the centrifugal force on the blade grip bearing is about 100 pounds.
06-10-2006 Over year old.
 
 
Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

Thanks for the math

Guy:

Its quite a load on them. Some info from SMB site:

Quote 

Load Rating

Dynamic load rating
The dynamic load rating is that constant stationary radial load which 90% of a group of identical chrome steel bearings, with only the inner ring rotating, can endure for one million revolutions before the first signs of fatigue develop. AISI440C/KS440 stainless steel bearings will achieve approximately 80% of the figure quoted. These figures are used in the calculation of life ratings and bearings should not be subjected to such loads in normal application. For life ratings, please contact SMB.

Static load rating
This rating represents the purely radial load which will cause a total permanent deformation of the balls or raceway equal to one ten-thousandth of the ball diameter. This may be tolerable for certain applications but not where smoothness and accuracy are required. Static load ratings for stainless steel bearings are approximately 75% of the load ratings for chrome steel bearings.

The load capacity of a bearing may be limited by the lubricant. Certain lubricants are only suitable for light loads while others are designed for high load applications. Load ratings are higher for full complement bearings (see Retainer). The axial load capacity of a radial ball bearing can be increased by specifying loose radial play.


Axial load rating
Small and thin-section deep groove ball bearings should not be subjected to axial (thrust) loads greater than 25 percent of the bearing's static load rating. For larger bearings (e.g. 6001, 6201, 6301 upwards) the figure rises to nearer 50 percent. To exceed the recommended limits will have a detrimental effect on bearing life.


Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
06-10-2006 Over year old.
HOMEPAGE  
 
 
Yug
rrProfessor
Location: UK. Herts

So seeing as the application is mainly thrust, which according to the SMB tech is 25% of radial, we are looking at a bearing capable of withstanding 400Lb axial load.
using 1 kgf = 2.2046 lbf, then we have kgf rating of about 180kgf. Granted the grips have 2 bearings, but might as well stick to 180 for a single bearing to be on the safe side.
According to the SMB site, the standard 5 x 10 x 4 has a dynamic load rating of 42kgf. That's way off the requirement. Have I got my math wrong somewhere
OR is this the explaination for failure that we've been looking for.

BTW, this is a MR105ZZ I've been looking at.
06-10-2006 Over year old.
 
 
Flying Tivo
Veteran
Location: Monterrey,NL,Mexico

They did not teach me math at Med school

But i think that is why the tails are failing.

Thanks a lot Guy

Felipe

If life throws at you lemons......Squirt some lemon juice in the eye of your enemy!!!!
06-10-2006 Over year old.
HOMEPAGE  
 
 
Yug
rrProfessor
Location: UK. Herts

Perhaps somebody at TT is in need of a good spanking
But seriously, it would be good for some more input on this because my findings above are not looking too promising
I might contact Bud at QUK for his views.
06-10-2006 Over year old.
 
 
md3dnt
Senior Heliman
Location: france

three dee nt tail on a raptor 90SE

after crashing 2 times because of the bad desingn of the tail of the raptor i finally put a three dee nt tail on my raptor. The tail contains trust bearings and seems to be very safe as compared to the original TT system
i will post pictures soon and let you know how it works
06-14-2006 Over year old.
 
 
PaulJC
Elite Veteran
Location: Hertfordshire UK

I'd be interested to hear the views of QUK, i was/am considering 2 of their new tail assy's however there is little point if the bearings are the faliure point, i've fitted SUS hubs and new bearings to both of my machines as a 'hope this helps until something better comes along' mod.

Quote 
To exceed the recommended limits will have a detrimental effect on bearing life.


That doesnt sound very promising
06-14-2006 Over year old.
 
 
Barney
Key Veteran
Location: Inverness Scotland

I e-mailed Bud..Apparently the problem is TT are using low quality bearings..Quick UK only use top quality japenese brgs

What I have done is to fit a thrust brg in place of one of the Radial brgs..
It's not as tidy as I would like but it works OK

I'm using the Quick Uk SUS hub

To cut a long story short I fitted a 5X10X4 thrust brg to the INNER side of the holder with a std 5x10X4 radial to the outside. (ideally it should be the other way round, but is not possible using two 5X10X4's etc...)

The TT tail blade grips are a little generous size wise allowing you to fit a thin shim between the brgs to prevent them binding against each other.

The thrust brg is fitted with the large hole to the hub. This allows the smaller end..with the small hole to rotate within the grip. The shim sits between the brgs..with the standard brg to the outside... BTW the shim is from a Robbe Millie tail gearbox..

As you have fitted a thrust brg + a shim it is no longer possible to torque the brg retaining bolt down as it will bind the brgs before bottoming out against the shank of the tail hub.

You can get round this by using some RED loctite (permanent) on the screws to prevent them backing out. Should you need to replace the brgs at a later date it will require some heat to break the bond...

As I said it's not perfect..but at least I won't be having another tail blade assembley whizzing past my Lug
06-14-2006 Over year old.
 
 
eric
Senior Heliman
Location: Fernley, Nevada

thrust bearing

http://www.vxb.com/page/bearings/PROD/HPI/Kit7149
06-14-2006 Over year old.
 
 
PaulJC
Elite Veteran
Location: Hertfordshire UK

Quote 
I e-mailed Bud..Apparently the problem is TT are using low quality bearings..Quick UK only use top quality japenese brgs

I would imagine most bearings used are japanese, do the bearings used by QUK have a different rating than those used by TT?

I am suprised that they have gone do the trouble of designing a new hub and grips assy and not modified it in some way to incorperate a thrust bearing, it is a nice looking piece of kit though
06-15-2006 Over year old.
 
 
md3dnt
Senior Heliman
Location: france

quk tail would be the same prob since they did not includ thrust bearings
my trial with the three dee nt tail works nicely !hope it will continue
06-15-2006 Over year old.
 
 
Barney
Key Veteran
Location: Inverness Scotland

Paul..The TT brgs are allegedly low quality chinese items
06-15-2006 Over year old.
 
 
donlynn
Key Veteran
Location: New Zealand

Gidday

I too have had several tail failures, all due to the grub screw failing where it exits the hub.

fixes which have worked to date and since i have had no failures in last 2 years (was about 2 per year)

1. only just nipping up the grub screws

2.holding nyloc nuts against grinding stone to remove radius on side opposite nylon so nut contacts bearing rather than yoke, I was going to use a washer as suggested in a earlier post , less parts ~ less to fail

3.replace grub screws after any contact with the ground( I had a bag of 20)

4. Preflight, I check grips for end float and smooth rotation(as best I can) before EVERY flight. this endfloat check has picked up potential failures in a lot of choppers I have checked.

I have the TT SUS part but havnt got around to fitting it yet.

In my limited experience the tt bearings ARE crap. No alledged about it, especally the washout mixing arm bearings, hey its a entry chopper ! I'm still having fun


Regards Don
06-15-2006 Over year old.
 
 
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