RunRyder RC
WATCH
 1 page 977 views POST REPLY
HomeAircraftHelicopterHelicopter Main Discussion › Leading or trailing main grip links ?
08-17-2010 05:25 PM  8 years agoPost 1
GyroFreak

rrProfessor

Orlando Florida ...28N 81W

My Posts: All  Forum  Topic

I have seen both and wondered what the advantages are of each type ?
Of course re-programing the radio would be required to reverse any setup.

I think about the hereafter. I go somewhere to get something, then wonder what I'm here after ?

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 05:38 PM  8 years agoPost 2
BarracudaHockey

rrMaster

Jacksonville FL

My Posts: All  Forum  Topic

Some claim leading edge is faster, I know that trailing edge links like the Raptor if you get a blade go out of track that it will pull down on the link and add pitch making things worse, if you have leading edge it pull the pitch down bringing the blades back in track.

I wouldn't rebuild any stock helis to get one or the other. Some guys used to do it to the Raptor but that was in lieu of fixing whatever was actually worn.

Andy
AMA 77227
http://www.jaxrc.com

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 05:40 PM  8 years agoPost 3
T-Squared

rrApprentice

SMRCF, GA

My Posts: All  Forum  Topic

Leading main blade grips are the best as they introduces negative feedback into the control system which improves the overall stability.

Without going into the technical detail (which is quite involved), with leading blade grips when a control input is made then any overshoot due to instability tends to be automatically reduced and dampened out. With trailing blade grips the opposite can be true and tends to rely on brute force within the servo control loop to prevent the instability developing into something bad.

Having said that, don't be scared of trailing blade grips in the RC world. There are a lot of highly successful ones out there, the Raptor series (pre Titan SE) being perhaps the most notable. It is simply that from a control theory viewpoint leading blade grips offer some definite benefits.

PM  EMAIL  Attn:RR  Quote
08-17-2010 06:25 PM  8 years agoPost 4
T Koffler

rrVeteran

Cayuga, NY 13034

My Posts: All  Forum  Topic

I thought by controlling the blade by the leading edge you gained mechanical advantage (more leverage).. I'm no engineer, I might be wrong but that's always what I though...

TK

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 07:22 PM  8 years agoPost 5
T-Squared

rrApprentice

SMRCF, GA

My Posts: All  Forum  Topic

No, the leverage is the same both ways.

A simple way to think of what is going on is to consider what happens when you put in a request for mor positive pitch. On the advancing blade (left for a clockwise rotor) which has the higher airspeed the balde will try to rise more. With a leading blade grip that rise will tend to take some of the pitch back out thus stabilising the situation. With a trailing edge grip it would try to put even more pitch in thus making things worse.

The opposite happens on the slower, retarding blade on the other side.

The above is not a technical accurate or complete description of what is going on but should give you the basic idea of the difference between leading and lagging grips.

Bottom line is that from a stability and 'good design practice' standpoint the blade grips should always be on the leading edge.

Ron.

PM  EMAIL  Attn:RR  Quote
08-17-2010 07:32 PM  8 years agoPost 6
T Koffler

rrVeteran

Cayuga, NY 13034

My Posts: All  Forum  Topic

I'm pick'n up what your lay'n down now.... I remember when the raptors came out I bought one and on the first flight it "woofed" really bad.. After chasing the problem for some time I ended up doing the grip flip... never had another problem with it..

TK

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 08:09 PM  8 years agoPost 7
Heli_KV

rrKey Veteran

Ottawa, Canada

My Posts: All  Forum  Topic

Rave has trailing edge grip links. I can hardly say that Rave is not utilizing 'good design practice'.

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 08:40 PM  8 years agoPost 8
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

With trailing blade grips the opposite can be true and tends to rely on brute force within the servo control loop to prevent the instability developing into something bad.
So the flybar does not stabilize the head ?

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 09:16 PM  8 years agoPost 9
BarracudaHockey

rrMaster

Jacksonville FL

My Posts: All  Forum  Topic

Has nothing to do with that. When the axle (spindle) compresses the dampener upward a rear link pulls down on the trailing edge increasing blade pitch, it's pretty simple.

Andy
AMA 77227
http://www.jaxrc.com

PM  EMAIL  GALLERY  Attn:RR  Quote
08-17-2010 09:41 PM  8 years agoPost 10
Derek Round

rrNovice

Bradford, UK

My Posts: All  Forum  Topic

This is an interesting thread! There's a lot of missunderstandings out there regarding this issue. So working from basic principles....and trying to answer the question.....Actually it's not which type to use, but which way has been designed into the head! You see, either will work, but the head must be designed so that cyclic pitch controls from the swashplate provide a "stable" movement of the rotor disc. For example, if we wish to roll or tilt the rotor disc to the right, as the disc moves and follows the swashplate (also tilted to the right), it is vital for stability that as the disc approaches the plane of the swashplate, that the cyclic pitch changes of each blade reduce to zero, so the disc ends up parallel to the swash. This also means that any "disturbance" to the disc plane is "resisted" and it is always brought back parallel to the swashplate. So whether a leading link or a trailing link is used, is actually irrelevant!
To put it another way, if a cyclic positive pitch is applied to a blade, as the blade rises, the blades pitch MUST decrease, so that as it becomes parallel to the swashplate, it stabilises and then stays parallel to the swashplate.
I hope that's clear?
It's taken me a long time to have a pretty good idea what's happening at head level, and I haven't mentioned gyroscopic precession or the reason for the flybar yet!
Enjoy!

PM  EMAIL  Attn:RR  Quote
08-17-2010 10:12 PM  8 years agoPost 11
PC12DRVR

rrKey Veteran

USA

My Posts: All  Forum  Topic

t. When the axle (spindle) compresses the dampener upward a rear link pulls down on the trailing edge increasing blade pitch, it's pretty simple.
Ahh,,, much better explanation now I understand what you mean.

PM  EMAIL  GALLERY  Attn:RR  Quote
08-18-2010 03:24 PM  8 years agoPost 12
Derek Round

rrNovice

Bradford, UK

My Posts: All  Forum  Topic

This is a VERY complex subject! Taking the posts so far.....
PC12DRVR....'Fraid its not as simple as that, as just reversing the main grip link without changing anything else mechanically, will always make the head (rotor disc) unstable, ie it won't follow the swashplate!!!
Barracudahockey.....Again, if this was to happen with a trailing link, then again the rotor disc would be unstable, and again the rotor disc would not follow the swashplate.
T-Squared.....you are right with your explanation with a leading main grip link, and also with a trailing link, assuming nothing else was changed. So you might ask how is it done successfully with trailing links?
The answer is to realise that for a trailing link the pivot point for the blades rising and falling vertically, is moved out away from the hub centre, usually well past where the link connection is. On my Concept 60 (fraid I only fly vintage helis), which uses trailing links, a quick waggle of the main blades up and down will confirm that this is true. And this means that as the blade rises, its pitch decreases, an obvious requirement for disc stability!
To conclude, neither is best. Both will work, with the correct mechanical design!
I hope this helps?

PM  EMAIL  Attn:RR  Quote
08-18-2010 03:59 PM  8 years agoPost 13
T-Squared

rrApprentice

SMRCF, GA

My Posts: All  Forum  Topic

Thanks Derek - fascinating subject... has to be good for at least a few beers

Ron.

PM  EMAIL  Attn:RR  Quote
WATCH
 1 page 977 views POST REPLY
HomeAircraftHelicopterHelicopter Main Discussion › Leading or trailing main grip links ?
 Print TOPIC  Make Suggestion 

 4  Topic Subscribe

Wednesday, December 19 - 1:24 pm - Copyright © 2000-2018 RunRyder   EMAILEnable Cookies

The RC discussion world needs to consolidate. RR is now one choice for that. Its software is cutting edge. It hosts on-topic advertising. Help RR increase traffic buy making suggestions, posting in RR's new areas (sites) and by spreading the word.

The RunRyder Difference

• Category system to allow Rep/Vendor postings.
• Classifieds with sold (hidden) category.
• Classifieds with separate view new.
• Answer PMs offsite via email reply.
• Member gallery photos with advanced scripting.
• Gallery photo viewer integrated into postings.
• Highly refined search with advanced back end.
• Hosts its own high end fast response servers.
• Hosts thousands of HD event coverage videos.
• Rewrote entire code base with latest technology.
• No off-topic (annoying) click bait advertising.
Login Here
 New Subscriptions 
 Buddies Online