DFC head slop?

[Heli$]

Hi guys, I've had my 700L top for maybe 9 months and noticed there is play in the head. Specially, if I move the blade grip up and down, there is play between grip and head block.

The heli doesn't have a ton of flights on it, maybe 60ish? Should I shim the head or maybe the stock DFC DAMPERS are already wearing out? If I shim, where have you guys been putting the shims?

Everything in the head is stock and built according to manual.

[Dawiev]

Hi, the dampers seems to be most suspect to premature wear. There has been a number of posts on this here and in the nitro forum.

Consider Trueblood dampers and a few aftermarket companies sells o-rings to put behind the dampers too.

https://www.helifreak.com/showthread...hlight=dampers

[Heli$]

Thanks for the help Dawiev, think I'll get some new dampers.

[Heli.Maniac]

This happens when the dampeners wear out. Since these DFC dampeners are solid plastic instead of rubber, the slop is a lot more pronounced. Before fitting the new dampeners in (assuming that you will use the stock Align again), check for any slop between the dampener and the head block as well as between the dampener and the spindle shaft. I have had a case or two where the dampeners where not machined well and the fit was loose causing slop after very few flight. Also don't forget to use some thick synthetic grease, I have been getting a lot more life out of them with good lubrication.

[RC/DC_5000]

Yea I would replace the dampers. This DFC damper problem is also on the 600L and 450L, where the black POM damper gets mashed and compressed fairly easily. When they do, it allows the FS to float too much which can lead to premature bearing wear and possibly worse.

Somewhere in a manual, I saw Align recommend to take the head apart like every so often. I can't remember how many flights exactly, but it was OFTEN. 9 months of flying is way past what they recommend. I'm talking about checking it every 30 flights or something. But of course, it depends on how hard you fly it.

SAB shims their heads and says the tighter the better. Their dampers don't seem to crush as easily either. IMO, Align wants the dampers their way so that the head runs smooth and never shakes and shudders... ever.

If you shim up the SAB head a mm too far, it will bob on the elevator axis until you idle up. You could shim the Align head the same no doubt, I just don't trust crushing those dampers anymore, if Align doesn't.

If anything, I'd look for aftermarket dampers.

[Heli$]

K, should I go true blood or KBDD limes?

There is no in out play so shimming may not work.

[RC/DC_5000]

IMO KBDD are too soft. I've found good luck with the Green Truebloods if you can find them. In fact, I won't even bother with any other damper in my 450L. But be warned, the Trueblood dampers are longer.. and make the head more rigid. Which is what you want in a way. But at lower RPMs, I pretty much guarantee you will get some shakes and shudders.

It's hard to have your cake and eat it too. Align's way allows your cake and eating it too... but its only for a short while. Talking high maintenance. Align's way will run perfectly at low RPM and even better at high RPM. But it won't last long.

[Heli$]

K. I got some KBDD and truebloods

Rcdc, I run 2000 to 2100 rpm, is that high enoug for the truebloods?

Thanks

[RC/DC_5000]

Yea I'd think so... I usually get the shakes and shudders when doing low rpm for takeoff and landing. I hate when the helicopter jumps up with full rpm. I like to land nice and softly and take off nice and easy.

It probably won't be in your idle up. More like 1800-1900 and less.

[Heli$]

Thanks

Hopefully it gets rid of that slop.

Do you have any slop with the truebloods?

[Ah Clem]

"K, should I go true blood or KBDD limes?"

The KBDD Lime Greens work great in the older Align 700 FBL heads, but we do not recommend them for the DFC heads.

The DFC heads should not be allowed to flap and really need solid dampers. If they flap, there is the danger of damage to the ball links or the bolts retaining the arms to the blade grip arms (as the arms are not flexible). Not good in flight.

I know it is odd for a manufacturer to suggest not using their product, but there it is.

KBDD Dampers work well on the SZ (Compass) driverless heads which are designed to allow flapping due to the flexible drive tubes or arms, but not the DFC heads with rigid arms, if that makes sense.

[Heli$]

Thanks ah Clem!

[Heli$]

Well, I put in the true blood dampers and there was significant in and out play which would have required shimming. I didn't bother and just put some new stock DFC dampers in. There is some up and down mov meant on the grips but not as bad as before.

What do you guys do to make the true bloods work, do you shim it?

Thanks.

[Heli.Maniac]

For in and out play, you need more shims. Usually one more shim on each side does the trick but you may need 2 to account for some play that will be created after dampener break-in. This applies to all dampeners that are made of rubber.

[Heli$]

Ok, it just seemed the lateral movement was significant with the truebloods which would require a lot of shims. I've never had to shim that much and found it unusual. It would take 2 thick washers or maybe 4.

[Sirolf]

Originally Posted by Ah Clem

"K, should I go true blood or KBDD limes?"

The KBDD Lime Greens work great in the older Align 700 FBL heads, but we do not recommend them for the DFC heads.

The DFC heads should not be allowed to flap and really need solid dampers. If they flap, there is the danger of damage to the ball links or the bolts retaining the arms to the blade grip arms (as the arms are not flexible). Not good in flight.

I know it is odd for a manufacturer to suggest not using their product, but there it is.

KBDD Dampers work well on the SZ (Compass) driverless heads which are designed to allow flapping due to the flexible drive tubes or arms, but not the DFC heads with rigid arms, if that makes sense.

I've been using lime dampers in the DFC head for a couple years now. Even in my 600. They do a good job. What would be recommend in your opinion?

[Ah Clem]

Sirolf,

Probably the stock Align, solid ones.

I feel very awkward recommending against one of our products, by the way. I have been flying my old, pre-DFC Trex 700 with the Lime Green KBDD Dampers again, for a few weeks now (it has not been off the shelf for a couple of years). It was a test vehicle for the Lime Greens before they were released to the public-the original test sample is still in the head and still in great condition. I would strongly recommend them for the original Trex 700E head.

Due to the design of the DFC head (rigid arms to drive the swashplate) anything that would allow spindle flapping (such as flexible dampers) would not be a good idea, IMHO (it will stress the links and the bolts that attach the DFC arms to the blade grip arms).

Align used solid dampers for a reason in their design. From what I have read, people who keep the solid dampers in the head and in good condition (i.e. no wear allowing flapping) have good service from the head.

I have not tried the TrueBloods, but it would be inappropriate for me to comment on them anyway, as they are a direct competitor.

[Sirolf]

To be honest, i have not had any problems with the lime ones and i change the plastic links if there is even the slightest play noticable.

The spindle is still rock solid and last time is had some movement in the bladegrips is because of worn bearings.

[Ah Clem]

Sirolf,

I like to see people using our products-I am just trying to do the right thing here.

I appreciate your feedback (and the fact that it is based on your actual experience).