RunRyder - Chinese weights on the tail grips

rrTV-PHOTO

New HD TV

HOME rrTV-PHOTO GALLERIES MY GALLERY HELP-FAQ

myHOME PM pmRR MEMBERS 650 ONLINE 21 EVENTS SEARCH REGISTER START HERE

11 pages [ << < 9 10 ( 11 ) > >> ]

8412 views

POST REPLY

A Main Hobbies	.	Boca Bearings	.	Modefo's RC Helicopters
	.		.

Main Discussion > Chinese weights on the tail grips

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

On the stock Raptor-50, I have tried two 1.5gm weights per blade at the blade grip base and it's still not enough to balance the forces. It seems to have reduced the forces to a bit less than half. I still measure about a pound of force on the pushrod with about 25º tail blade angle and running at 9140 rpm.

I'm thinking that's a good number because that leaves me with a servo load of about 10 oz in at about 25º tail deflection and using a 17mm servo arm. This is about as heavy as I would want to go with the weights

You can see I used cut and folded 1mm sheet steel and replaced the standard 2.5x10mm bolt with a 2.5x15mm bolt.

It was interesting at first because the test Raptor had my On-Board-Alternator and there was enough friction in the one-way to drive the alternator to make the electronics come alive when I wound up the main shaft to 2000 rpm

11-12-2007 Over year old.

HOMEPAGE

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

So who has a Raptor V2 using stock PV-0148 tail grips with good flight skills to test some weights for me to see how they improve gyro operation ?

11-14-2007 Over year old.

HOMEPAGE

HeliPhil
Senior Heliman
Location: UK

I tried my own non-scientific experiment and added an extra nut on each side of my R50 tail grip bolts ( I did have to put a slightly longer bolt on). Flew it on Sat and I can't say I noticed any difference but hopefully my tail servo did. I will leave them on for now and hope the extra stress does not blow apart my tail assembly...
(still using original 3 year old tail assembly)

http://www.olsonracing.co.uk

11-21-2007 Over year old.

HOMEPAGE

lesodell3
Senior Heliman
Location: michigan usa

aah words to live by. "A side note, vigilante behaviour will be squelched!"

12-06-2007 Over year old.

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

Food for thought,

If the tail blades are flexible enough, will they wash-out (de-pitch) at the tips and end up being pitched more like a propeller ? Making the tail blades more efficient ?

01-04-2008 12:56 AM

HOMEPAGE

Yug
rrProfessor
Location: UK. Herts

HeliPhil - it's not just a case of adding a nut because the system really needs to be tuned to optimise loading. This will be a combination of both grip and blade types. The tuning is most easily accomplished by strapping down the heli and spooling up (without main blades) using an electric drill or alike. Holding the tail pushrod in your hand will give you good feedback as you tweek the weights. If your tail grips don't use thrust bearings I would be very cautious because they could let go, so some protection would be advised.
Your comment about not noticing any difference is valid because, depending on your tail servo, it is entirely possible that it could adequately overcome the TB forces in conjunction with your gyro. However, the big advantage as I see it is that with the pushrod forces being minimised, the servo is doing much less work with the result that longevity and general wear are improved. Depending on your tail servo, this mod would return better performance on for example an 8700G compared to a 9651.
Why make a component undergo unnecessary stress ?

Vegetable rights and Peace

01-21-2008 02:03 AM

Tmblewd
Veteran
Location: Phoenix, AZ

What about other Helicopters? In therory if this works on a TRex or Raptor is it going to work on other Helis? Is this something that the Helicopter manufactures are going to need to look at? Or is this MOD left to those who want it to figure out how much weight is needed for their Heli?

01-21-2008 03:54 AM

Yug
rrProfessor
Location: UK. Herts

It applies to all helis although some manufacturers have already taken care of it. Perhaps those manufacturers that have chosen to ignore the problem have felt there is no problem provided you use a powerful enough servo and it's acceptible that the servo is having a hard time.
The problem is that every grip/blade combination needs to be tuned differently so this job is down to the individual builder.

Vegetable rights and Peace

01-21-2008 08:55 AM

Tmblewd
Veteran
Location: Phoenix, AZ

Yug - Well, if this is a math exercise, I'm out. That's not my strong subject. If it's add weights and experiment that's my area. And if it's left to the Helicopter Manufacturers, how many do you think are really going to spend the time and money to figure it out for all their models?

01-21-2008 03:41 PM

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

It doesn't take that much to figure out. Go back in this thread and check my comments.

01-21-2008 03:53 PM

HOMEPAGE

HeliPhil
Senior Heliman
Location: UK

Hi Yug
It was not completely unscientific as I calculated that the extra weight would be approx 1 gram per blade holder. This was less than had been quoted and I reasoned that a small reduction in force required by the servo and low weight increase (not to increase stress on the blade holder) would be a worthwhile to give my 9253 a less stressful life. Without measuring it I don't know how much if any that I have gained but equally I certainly have not lost anything. Its been on for a couple of months now and afaik its staying.

http://www.olsonracing.co.uk

01-21-2008 03:58 PM

HOMEPAGE

Yug
rrProfessor
Location: UK. Herts

Tmblewd - Doesn't need to be a maths exercise and is best solved empirically due to the number of variables. If you look at the new G-Force grips, they have an M3 hole in the weight to allow fine tuning.

Vegetable rights and Peace

01-21-2008 04:33 PM

Tmblewd
Veteran
Location: Phoenix, AZ

Quote
One thing I would stress is to only do this mod with grips incorporating thrust bearings. I wouldn't recommend using stock grips because the added weight of the weights will simply load up the radial bearings even more. If you look at the bearing specs, and do the maths on the forces, these bearings are already being overloaded by a factor of 2. Thrust is a must.

From YUG back several pages

This all started by doing this mod to a TRex. Your statement above pretty much takes out a lot of helis. How many Helis actually have thrust bearings in the tail rotor grips?

01-21-2008 07:53 PM

AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

Earlier in this thread I came up with about 31 lbs of centrifugal force on a R-50 tail blade and with my tested location for weights, about 1½ lbs was added.

01-21-2008 08:04 PM

HOMEPAGE

Yug
rrProfessor
Location: UK. Herts

Quote
Your statement above pretty much takes out a lot of helis. How many Helis actually have thrust bearings in the tail rotor grips

Very fair point. I can only go from personal experience and bearing specifications, in so much as I am dumbfounded as to why any heli manufacturer could produce tail grips without thrust bearings when you consider the thrust specifications for radial bearings are far exceeded by the centrifugal forces of the tail grip and blade. When head speeds get close on 2k then the forces on the tail blades really mount up to the point where the bearings are at breaking point. This exact thing happened to me a few years ago so I did a little mod using a washer with plastic grips so that even if the bearings parted, the grip wouldn't fly off. I then started using the new QUK grips. Guess what, the bloody thing let go in the 1st few flights, so I discussed this with Budd which resulted in the thrust bearing revision. Manufacturers are beginning to take note of this thrust bearing issue and for those that aren't, an upgrade can usually be found somewhere.

Vegetable rights and Peace

01-21-2008 08:50 PM

Tmblewd
Veteran
Location: Phoenix, AZ

Yug - I think your information is quite useful. Am I going to incorporate it into all of my helis? Probably not. I will do the mod to my TRex and my Lepton and see what I gain. But trying to figure out how much weight is needed to equal out the centrifical forces is more than I really want to mess with.

Yes, I will agree that the Heli manufacturers really are not going to spend the money to fix the tail rotor grips. I personally feel that it would cost too much money to add thrust bearings into their tail rotor grips to get enough of a return for their investment. I think they will leave it to someone to make Aluminum Upgrades with the added weight, but leave it to them to figure out the added thrust bearing. Time will tell what happens when it comes to Thrust Bearings. I think all new Heli designs will have them already installed in the tail rotor grips.

01-21-2008 11:19 PM

Morris
Senior Heliman
Location: Hong Kong

AirWolfRC, Yug and Tmblewd,

I have been reading this thread and coming to a lot of scholar terms and calculations.

I am not good in this so I am thinking of making the tuning of weight by "rule of thumb" under the assistance of electronic means; let say, use of EagleTree to monitor the tail servo activity, movement and/or current draw ... while changing the weight. Then we pick the weight that gives the least movement (gyro correction) and/or current draw without stick input. I think this practically will do.

My HO, what do you think? Please comment

01-21-2008 11:33 PM

Yug
rrProfessor
Location: UK. Herts

You need to be careful that you don't use too much weight because it will cause the grips to want to go to full pitch - just in a similar way that without weights, the blades go to zero pitch.
At full pitch, the piro rate will be ballistic while at zero pitch, not quite so.
In the setup, it's good to maintain a small zeroing force for this reason, and a fraction of a gram with its CG at some radius makes all the difference.

Vegetable rights and Peace

01-22-2008 12:06 AM

Morris
Senior Heliman
Location: Hong Kong

Yug, that happened months ago already, I put too much on my Trex 600 EP and it crashed on spool up when the weight pull it too full pitch ...

01-22-2008 10:03 AM

11 pages [ << < 9 10 ( 11 ) > >> ]

8412 views

POST REPLY

XHELI.COM	.	Autography FlightPower	.	Advantage Hobby
	.		.

Main Discussion > Chinese weights on the tail grips

PRINT TOPIC

Advertisers

Subscribe to This Topic