DFC!? Pah! ......

[Guest]

If he gives me his credit card details I can be whatever he wants me to be..!!!

[MarkG_R1]

DFC!? Pah! ......

Dfc all the way for me
I don't know any different as my first fbl was my converted 450
I love the way they look and fly

[tomatwalden]

DFC!? Pah! ......

If he gives me his credit card details I can be whatever he wants me to be..!!!

Here ya go, let me know how you get on with it !

ImageUploadedByTapatalk1361463191.871790.jpg

[George J]

I make no bones about the fact I'm dubious of DFC designs. I do understand that they lower the rotor disc, making cyclic response more crisp.

But, look at this picture of my Align 500efl pro rotor head next to the goblin 500 hps rotor head.

Look at the difference in distance between the blade grips and swash plate ( both with swash driver arms at 90). You don't need DFC to lower the rotor disc, you just need a good head design!

[ATTACH]55796[/ATTACH]

I couldn't agree more although not just with the Goblin design. I'm changing my 700 DFC back to a conventional swash follower design as I just think that the DFC design is a compromise but I do prefer the lower head so one of these bad boys is sitting on my bench ready to go onto my 700 when I get a chance and I know it's going to be better.

KDE Direct - TREX 700 Series SXT Main Rotor Head System

Its only 10mm higher than the Align DFC head but has all the positives of a conventional head design, quality looks awesome as well.

George

[heathy]

Tom, less time on here please and more time building, whats the matter with you man.

[tomatwalden]

Tom, less time on here please and more time building, whats the matter with you man.

Less haste, more speed! The build is coming along nicely - VX1 hopefully arrives tomorrow. Grassroots will put a temporary halt on proceedings, but it'll definitely be ready for it's maiden sometime early next week.

[VOLT]

QUOTE=tomatwalden;980552]I make no bones about the fact I'm dubious of DFC designs. I do understand that they lower the rotor disc, making cyclic response more crisp.

But, look at this picture of my Align 500efl pro rotor head next to the goblin 500 hps rotor head.

Look at the difference in distance between the blade grips and swash plate ( both with swash driver arms at 90). You don't need DFC to lower the rotor disc, you just need a good head design!

ImageUploadedByTapatalk1361439380.624293.jpg[/QUOTE]

Dear Tom
before ya start throwing big words like "DFC PAH!" around you should know DFC has got nothing to do with lowering the head....the lowered head is a by product of the DFC "DIRECT FLIGHT CONTROL" arms that remove the anti rotation swash link arms you can change the length of the main shaft by adjusting the lenght of the Down links as I have in many of my own designs here is a photo of a real DFC head ....DFC cleans up the head from all that clutter and there are many ways to do it not just Aligns copyed way...


and a vid of one of my 1000's head design

cheers

H

[VOLT]

and an RJX head with Align downlinks converting the head to DFC ...I cut my main shaft down by 15mm so has excellent numbers in the setups...

a vid of my heli flying with the RJX head

[trillian]

The bigger picture is that ultimately there are two goals;

1. Raise the C of G
2. Make the main shaft more rigid by reducing the amount of shaft between the upper bearing block and the rotor hub.

These elements were (among other things) what the Henseleit TDR was designed around. But on the TDR most of the electrics, servos etc. are situated above the boom and the boom is positioned where it is owing to the main gear and tail drive being situated very low. So it brings the C of G up but keeps the boom a safe distance from the blades.

There's no magic to the DFC design by itself - it's not going to relay swash movement to the grips in some ethereal mystical way but it eliminates areas of potential slop and paves the way for lowering the head / raising the C of G (but, as someone has mentioned, the distance to the boom is then going to be the limiting factor).

[VOLT]

G-Day
no offence intended here but I must disagree Trillian

DFC

Its How the Bladegrip Connects to the Swash...thats it nothing more nothing less

somehow everybody thinks its the whole head and main shaft

its a glorified swash anti rotation device

other designers have the same principal with various length main shafts and various CG positions but the down link to the swash remains the same design ..all it does is stops the swash from rotating and removing the swash arm links and connection to the main shaft

the bigger picture you speak of isnt true..there are large scale helis out there with long DFC connections that dont use a high CG or need to make the shaft more ridgid they just use stronger thicker main shafts..its not just aplicable to stickbanging 3D heli setups

Cheers

Haydn

[tomatwalden]

Dear Tom
before ya start throwing big words like "DFC PAH!" around you should know DFC has got nothing to do with lowering the head....the lowered head is a by product of the DFC "DIRECT FLIGHT CONTROL" arms that remove the anti rotation swash link arms you can change the length of the main shaft by adjusting the lenght of the Down links as I have in many of my own designs here is a photo of a real DFC head ....DFC cleans up the head from all that clutter and there are many ways to do it not just Aligns copyed way...
H

Hi there. Please don't take offence by the thread title, I wrote it slightly in jest (I thought the word "Pah!" was sufficiently silly that nobody would think I was being too serious!) and deliberately to stir up a bit of discussion. It wasn't meant with any seriousness. However, since I've got your attention, and you seem to know what you're talking about - here's a question ... First, I should note that I'm working on the premise that the links from the swash on DFC are no more direct than normal swash links - it's simply that they also do the job of the swash driver.

So, short of the lower head (and therefore, CoG closer to the disc ) are there any other aerodynamic reasons for a DFC style approach. I get the argument about removing the mechanics of the swash driver - but surely that just increases work onto the swash links and blade grips does it not ?

ie. if a swash-driver was designed such that the main shaft was the same length as a DFC approach - which is better!? ... and why!?

Cheers. T

[trillian]

G-Day
no offence intended here but I must disagree Trillian

DFC

Its How the Bladegrip Connects to the Swash...thats it nothing more nothing less

somehow everybody thinks its the whole head and main shaft

its a glorified swash anti rotation device

other designers have the same principal with various length main shafts and various CG positions but the down link to the swash remains the same design ..all it does is stops the swash from rotating and removing the swash arm links and connection to the main shaft

the bigger picture you speak of isnt true..there are large scale helis out there with long DFC connections that dont use a high CG or need to make the shaft more ridgid they just use stronger thicker main shafts..its not just aplicable to stickbanging 3D heli setups

Cheers

Haydn

Your missing the point of what I'm saying. Of course you can have a DFC head with a long main shaft or low C of G but you will not experience any measurable benefit just by having a rigid arm that goes from the swash to the grips vs a regular link to the grips on a more conventional design provided the conventional head in question has no slop in any of the linkage. The problem with long DFC style linkage is that the phase will change if the feathering shaft teeters. The FBL controller will mask the effects but in an ideal world we want no movement in the swash phasing.

What you seem to be saying is that, if everything else remains constant, just by virtue of how the DFC grips connect to the swash provides some measurable benefit. I just don't see how because at the end of the day it's just a simple mechanical function. If the swash moves 2 degrees and the grip moves 2 degrees how can it matter what shape or form causes that movement? It could only come down to how rigid the connection is and now slop-free it is.

If someone can provide a logical, provable explanation of how the DFC accomplishes some kind of measurable benefit over a well designed and sturdy head like on the TDR or the Goblin then I am more than happy to change my tune.

(BTW - in that second image /video down (entitled 'metal pushrods') the head you're showing with the custom made guides is not a DFC head, you have conventional (omnidirectional) links on the grips. )

[Tommy]

Gotta say I'm a fan of Align's DFC design, the direct feel is awesome

[aww]

Has anyone see Smaktalk episode 30, Bobby Watts explains why he think DFC is an unsuitable design for anything bigger than a 450.
Anthony

[VOLT]

Your missing the point of what I'm saying. Of course you can have a DFC head with a long main shaft or low C of G but you will not experience any measurable benefit just by having a rigid arm that goes from the swash to the grips vs a regular link to the grips on a more conventional design provided the conventional head in question has no slop in any of the linkage. The problem with long DFC style linkage is that the phase will change if the feathering shaft teeters. The FBL controller will mask the effects but in an ideal world we want no movement in the swash phasing.

What you seem to be saying is that, if everything else remains constant, just by virtue of how the DFC grips connect to the swash provides some measurable benefit. I just don't see how because at the end of the day it's just a simple mechanical function. If the swash moves 2 degrees and the grip moves 2 degrees how can it matter what shape or form causes that movement? It could only come down to how rigid the connection is and now slop-free it is.

If someone can provide a logical, provable explanation of how the DFC accomplishes some kind of measurable benefit over a well designed and sturdy head like on the TDR or the Goblin then I am more than happy to change my tune.

(BTW - in that second image /video down (entitled 'metal pushrods') the head you're showing with the custom made guides is not a DFC head, you have conventional (omnidirectional) links on the grips. )

Greetings again

ok first you say (The bigger picture is that ultimately there are two goals;

1. Raise the C of G
2. Make the main shaft more rigid by reducing the amount of shaft between the upper bearing block and the rotor hub.)

then you say..(Of course you can have a DFC head with a long main shaft or low C of G) ok I missed the bigger picture there I must be blind

I dont seem to be saying anything..I am saying its just a link bewtween the Bladegrip arm and the swash removing the clutter of the other systems ,there is no advantage in flight controll at all,just cleans up slop if its a good system with good bearings in the downlinks

and the acronym of DFC are just some letters that some bloke sucked out his thumb while ripping the design off and had to think of a name, its just a sales pitch name its actually a Direct Swash Connection so should have been DSC if they paid attention to the simplest way of using english, "Direct Flight Control!" WTF is that?

BTW yes you are correct is not a DFC head I never said it was...what I did say was (DFC cleans up the head from all that clutter and there are many ways to do it not just Aligns copyed way..) but its still a connection from the bladegrip arms to the swash without a swash lock driver ..the arms only move up and down in the pitch range giving it the same direction use as a ALIGN DFC down link and the swash moves the same as it would in all heli deisgns..

SJM wher the first guys to use this system then Compass followed later

cheers

H