Chuck and Ryan's Build Tips

[ceslaw]

Tight Fits

1. Torque Tube. The torque tube was too snug to fit the torque tube masts. After reading posts about the tube getting stuck before it could be properly placed, I approached this step forewarned. Measurements of the tube revealed it was in the range of 1.501 – 1.502 while the mast opening was just barely 1.500. 220 grit sandpaper was used to sand the ends of the torque tube so it was just barely under 1.500. It took a fair bit of sanding to reach a point where it would just slide in.

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We sanded a couple of inches from the end of the tube so that the torque tube blocks would also fit properly, but shimming later proved necessary. That will be a topic for another day.

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2. Fuel Selector. The fuel selector has three fittings. Two are straight but on the bottom an angled AN9142D is used which must be pointed in a forward direction. The fitting supplied with the kit would not reach a snug point when pointed forward.

To solve the problem a couple of extra AN9142D fittings were ordered from Aircraft Spruce. It seems that there is some variation in the way the threads are cut so different fittings may end up in different positions when tightened. By swapping fittings one that snugged up in the correct position was found. (I now have some extra fittings I will gladly part with). The following images illustrate the different points where three fittings just began to snug up. The first came from Aircraft Spruce while number 2 and 3 came from Cubcrafters.

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The manual refers to using E Z Turn fuel lubricant on the threads. I used that stuff on the first plan and over time noticed that the lubricant tended to turn blue at the joints, suggesting there was some seepage. On this plane Loctite 567 was used which is a methacrylate sealant; a preferred solution.

Fitting number 1 worked perfectly. Twisting it back and forth helped massage the threads a bit, then the Lotcite 567 was applied, and it was turned a bit less than 180 degrees after it started to snug to its final forward facing position, where it was nice and secure.

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[PBY Catalina]

Tight Fits

1. Torque Tube. ...

2. Fuel Selector. The fuel selector has three fittings. Two are straight but on the bottom an angled AN9142D is used which must be pointed in a forward direction. The fitting supplied with the kit would not reach a snug point when pointed forward.

To solve the problem a couple of extra AN9142D fittings were ordered ...

The manual refers to using E Z Turn fuel lubricant on the threads. I used that stuff on the first plan and over time noticed that the lubricant tended to turn blue at the joints, suggesting there was some seepage. On this plane Loctite 567 was used which is a methacrylate sealant; a preferred solution.

It is always with the same pleasure that I read you!
I’m just a few steps ahead of you in my EX2 build.

It is very reassuring to see that I face exactly the same problems and, above all, that with a smaller experience than yours, I bring the same solutions!

For the elbows, I have exactly the same problem with the NPT lower elbow of the Brake Master Cylinder. I ordered 4 elbows from LAS in UK. (Same source of supply, but better service here in EU than Spruce). I’ll let you know if these new elbows are any better.

[ceslaw]

Shims.

In a previous post the slightly too large torque tube which required sanding to fit the torque tube mast was noted. Although the tube was also sanded in the area where the torque tube block is placed it proved to be too tight. Even though it seemed to fit well initially, when torqued down to 90-inch pounds it got stiff.

In retrospect, it would have been better to temporarily place the torque tube blocks in place, torque them to spec, and check for movement before the torque tube was installed. This would have permitted additional sanding to assure free movement when it would still be possible to sand the torque tube. Oh well. Maybe on the next plane.

Shims were used to solve the problem, as has been discussed by others. Shims were fabricated from brass stock, .005 thick, ½ x ¾ inches. A paper punch was used to make the center hole. Two .005 shims were used at the two front locations and three at the two aft locations resulting in smooth motion with some minimal resistance. It took some experimenting to come up with this arrangement, using different thicknesses and removing the bolts and loosening the blocks probably a dozen times before we were satisfied. The last time a fresh Nyloc nut was placed.

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The brass shims are just barely visible.

Note that too thick shims can result in some up and down movement of the torque tube, which is why sanding a bit more to get a good fit may be preferable.

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[Daveembry]

Chuck, what I also found was that what was causing the tightness wasn’t actually the size of the torque tube but the ANGLE of the blocks on the floor board. I would have one fitting nicely in the blocks but then I noticed once torqued down, no matter what, it would be tight. Then I noticed the blocks sit at a slight angle on the floorboard. Unless PERFECT in alignment with the torque tube, it would then BIND onto the tube when you tightened it down and it then hit the tube at an angle and makes it hard to rotate freely.

So, I sanded the bottom of the block to get the angle right against the floor board so it was perfectly parallel to the tube.

Shims.

In a previous post the slightly too large torque tube which required sanding to fit the torque tube mast was noted. Although the tube was also sanded in the area where the torque tube block is placed it proved to be too tight. Even though it seemed to fit well initially, when torqued down to 90-inch pounds it got stiff.

In retrospect, it would have been better to temporarily place the torque tube blocks in place, torque them to spec, and check for movement before the torque tube was installed. This would have permitted additional sanding to assure free movement when it would still be possible to sand the torque tube. Oh well. Maybe on the next plane.

Shims were used to solve the problem, as has been discussed by others. Shims were fabricated from brass stock, .005 thick, ½ x ¾ inches. A paper punch was used to make the center hole. Two .005 shims were used at the two front locations and three at the two aft locations resulting in smooth motion with some minimal resistance. It took some experimenting to come up with this arrangement, using different thicknesses and removing the bolts and loosening the blocks probably a dozen times before we were satisfied. The last time a fresh Nyloc nut was placed.

IMG_1209.jpg

IMG_1210.jpg

The brass shims are just barely visible.

Note that too thick shims can result in some up and down movement of the torque tube, which is why sanding a bit more to get a good fit may be preferable.

IMG_1219.jpg

[PBY Catalina]

Chuck, what I also found was that what was causing the tightness wasn’t actually the size of the torque tube but the ANGLE of the blocks on the floor board. I would have one fitting nicely in the blocks but then I noticed once torqued down, no matter what, it would be tight. Then I noticed the blocks sit at a slight angle on the floorboard. Unless PERFECT in alignment with the torque tube, it would then BIND onto the tube when you tightened it down and it then hit the tube at an angle and makes it hard to rotate freely.

So, I sanded the bottom of the block to get the angle right against the floor board so it was perfectly parallel to the tube.

Goood Morning USA,
Hi Dave, hi Chuck,

In my case, after precise measurements, it was both the thickness of the torque tube and also the wrong parallax of the blocks that was problematic. So I applied both of your solutions. In my case the shims where in aluminum. But using a punch is a great idea! (Maybe on the next plane!)

[ceslaw]

Very good point on the torque blocks being parallel. I did indeed confirm they were parallel, or if not it was too slight to be easily detected.

The Cub build five years ago did not have this issue. I wonder if Cubcrafters is using a fractionally larger diameter tube?

[Daveembry]

Mitch originally told me the tolerances on the torque tube pipe was .005 and he thought this was the isssue. Some tight, some not. I had one that was good in the blocks…..even after I tightened to 90 in lbs with the tube just in the blocks onto the tube (not installed in the floorboard)…..but when installed and torqued in the floorboard it bound up again. That’s when I saw the floorboard was angled slightly and when you torqued it down, it caused the problem. Mitch checked it out and saw that was at least, part of the problem……but it was never addressed in the manuals.

Very good point on the torque blocks being parallel. I did indeed confirm they were parallel, or if not it was too slight to be easily detected.

The Cub build five years ago did not have this issue. I wonder if Cubcrafters is using a fractionally larger diameter tube?

[ceslaw]

Good info Dave.

So the best approach would be to set every thing up, install the torque tube blocks, torque to 90 # and check for fit before the rear torque tube mast is riveted in place. That way any issues with binding could be sorted before the point of no return when the rear mast is riveted and cannot be removed. Also this would need to be done BEFORE the floor is screwed down, since that will likely contribute to the alignment issue.

That would be a good bit of information to add to the manual.

Then the question becomes solving the misalignment, if present. Perhaps the base of the torque tube block could be machined at a slight angle. Getting sufficient precision with a sanding block could be a challenge. I'm guessing it would be a tiny amount.

Or, in the alternative, one could add a few thousands inch of shims. Not as elegant a solution, but seems to work. The fact that ten thousandths was enough to make it move smoothly suggests the misalignment is not that great - but enough to bind it up.

Finally I wonder if it will wear into shape over time. If so, shims could be removed if it starts to feel a bit loose.

Appreciate your feed back. Thanks.

[Daveembry]

yes exactly. The last one I did, I assembled it all on the bench to the seatbase. I installed the rear blocks (mine have all been plastic and not metal) to the seat base and torqued. Then put front ones in place and torqued and checked the freedom of movement. When it was tight, I backed off the torque until it was smooth again. It usually worked good when the torque was off just a bit. I'm not sure how important 90 in lbs is???

Then I had to sand a bit off the bottom of the front block. I used a belt sander with a 400 grit to take off a very small amount at time and then rechecked until it worked.

I knew it worked fine in the individual blocks at 90 in lbs UNTIL it was installed on the floorboard.....so that angle was the culprit....

Good info Dave.

So the best approach would be to set every thing up, install the torque tube blocks, torque to 90 # and check for fit before the rear torque tube mast is riveted in place. That way any issues with binding could be sorted before the point of no return when the rear mast is riveted and cannot be removed. Also this would need to be done BEFORE the floor is screwed down, since that will likely contribute to the alignment issue.

That would be a good bit of information to add to the manual.

Then the question becomes solving the misalignment, if present. Perhaps the base of the torque tube block could be machined at a slight angle. Getting sufficient precision with a sanding block could be a challenge. I'm guessing it would be a tiny amount.

Or, in the alternative, one could add a few thousands inch of shims. Not as elegant a solution, but seems to work. The fact that ten thousandths was enough to make it move smoothly suggests the misalignment is not that great - but enough to bind it up.

Finally I wonder if it will wear into shape over time. If so, shims could be removed if it starts to feel a bit loose.

Appreciate your feed back. Thanks.

[ceslaw]

Pulleys and Washers. Getting two pulleys and five washers aligned in a narrow slot can be a challenge. Here is a simple solution.

Stack the pulleys and washers, well lubricated with white lithium grease. Insert a section of plastic tubing or something similar cut to the total length of the hole, then drop it in place. When the bolt is inserted, it will push the piece of tubing out and all those washers and pulleys will be all lined up.

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