Electric flap weldement “play”

I’m installing the weldement which moves the flaps. I’ve secured them on the sides into the plastic, notched pivot blocks. The blocks screws have been tightened to the bulkhead.

My question is how easy should this thing move up and down? Because now it takes a few pounds of pressure to rotate it. What would be the solution? Widening the holes in the pivot blocks? Or is this normal?

Bolts

nohoflyer said:

I’m installing the weldement which moves the flaps. I’ve secured them on the sides into the plastic, notched pivot blocks. The blocks screws have been tightened to the bulkhead.

My question is how easy should this thing move up and down? Because now it takes a few pounds of pressure to rotate it. What would be the solution? Widening the holes in the pivot blocks? Or is this normal?

Click to expand...

I found it very tight as well. Curious what others have done.
The rudder weldment was also really snug so I used a drilled bolts and castleated nuts to get the tension perfect then pinned with cotter pins. I can always adjust them tighter.

Misread this at first... Have you put the center block in yet or just the ends?

Get it completely assembled before modifying anything.

agent4573 said:

Misread this at first... Have you put the center block in yet or just the ends?

Click to expand...

Right now just the ends. Although it seems that right now the weldement is under less friction than if another block is added to the equation

same here. A bit of work with sandpaper on your finger will relax the bore a bit for freer movement.

Different approach...

Instead of trying to "open the bore" of the UHMW blocks, I used a piece of fine emery cloth and "red" 3M scotchbrite pads to polish the ends and middle section of the flap torque tube (aka weldment).

From there I beveled the ends of the tube with a 45° chamfer, debured, and worked over with some 400grit wet/dry to smooth the tube ends.

I applied a light coat of Lithium wheel grease (white, water proof) to the polished sections of the tube. Place two AN960-10 washers in between the center bearing block halves (F-680) -- this makes up for the material removed when you slice the block in half. Torque all AN3 bolts to spec (~25inLbs).

The torque tube should hold its position without drifting down, but be easy enough to move by hand without any "grunt."

--- As an aside, I upgraded the flap push rods (F-759A) to the hex version from the RV-9 (VA-256) --- I know, I know, it won't work...

Longeron Alignment ?

You might also consider checking the side-to-side alignment of the supporting longerons. If the flanges to which the UHMW blocks are attached are not in good "alignment", the blocks will "tip" just enough to make the drag you are talking a about when they are tightened down. Also, you might check the fore and aft alignment of the blocks in their mounting holes in the longerons - if the blocks are not parallel when bolted down, you will create drag as well.

My Rocket, required such "shimming".

YMMV - But it is worth considering.

HFS

Just me

I did not need to do anything to my blocks, but I did have to remove some of the powder coat (paint) from the rod to get it free.

I would make sure the blocks are running on the steel flap shaft without any powder coat interference.

HFS said:

You might also consider checking the side-to-side alignment of the supporting longerons. If the flanges to which the UHMW blocks are attached are not in good "alignment", the blocks will "tip" just enough to make the drag you are talking a about when they are tightened down. Also, you might check the fore and aft alignment of the blocks in their mounting holes in the longerons - if the blocks are not parallel when bolted down, you will create drag as well.

My Rocket, required such "shimming".

YMMV - But it is worth considering.

HFS

Click to expand...

The blocks are bolted to a bulkhead not the longerons.

Final post on this….

Well third install was a charm. I spoke to builder support for some other ideas.

1. I both sanded the weldement and the blocks a bit.

2. I loosened the torque on the attachment bolts. Vans said the normal torque values are for securing metal and in this case we are compressing plastic and that some distortion may occur if you crank on the nuts. So I backed off a bit.

3. Used white lithium grease on the ends and the blocks.

The end result was a much smoother movement. After reading some posts on flap motors going bad I had a bad feeling about all the friction. Thanks for all the suggestions !

nohoflyer said:

Final post on this….

Well third install was a charm. I spoke to builder support for some other ideas.

1. I both sanded the weldement and the blocks a bit.

2. I loosened the torque on the attachment bolts. Vans said the normal torque values are for securing metal and in this case we are compressing plastic and that some distortion may occur if you crank on the nuts. So I backed off a bit.

3. Used white lithium grease on the ends and the blocks.

The end result was a much smoother movement. After reading some posts on flap motors going bad I had a bad feeling about all the friction. Thanks for all the suggestions !

Click to expand...

This is the exact info I was just looking for: I find that torqueing bolts through UHMW plastic blocks tends to distort the blocks. Good to hear that we can go lighter on the toque.

UHMW cant be opened up with emery cloth ...
The hole in the UHMW are not absolutely round ...
The tubes are not absolutely round ...

Suppose the largest diameter tube comes onto the smallest plastic diameter during the partial rotating and vise versa. high friction is generated.

Measure the tube and plastic work with the emery cloth on the high-points of the tube and on the smallest positions of the plastic (but also on the tube).

Plastic should not be lubricated with mineral oil-based lubricant! It will swell the plastic (with time), look for a special approved plastic lubricant.

UHMW is self lubricating. If your weldment is binding or has a high friction component, fix it. Lubricating is just masking the problem and sets up another maintenance item.
These journals should be maintenance free for life when properly fitted.

Also, those flap motors are geared and a lot more powerful than one thinks. I haven’t heard of a flap motor failure due to overload. The common failure used to be grease migration interfering with the commutator in the motor.

Mine were tight as well.
In a previous work situation, we used a lot of Delrin(UHMW). You can sand it but it just makes it grow hair and often makes the issue worse. I don't like grease either.
Reduce the torque on the bolts.
If you find it is binding address that first and if you still need a little help add some graphite. I wouldn't use anything that attracts particulate, like grease myself.

My $2 worth of advice.