Torque tube.

[Daveembry]

No fun Daveembry.

I disassembled my front stiffener and torque tube bushing assembly after I finally got the aft mast free. Then I sanded the aft end of the tube and test fit the aft mast several times before I was confident I could do it with the tube installed thru the floor. I have not put the aft mast in place yet.

Now that I have put the forward torque tube bushing assembly back together and torqued the AN4-24A bolt and AN365-428A nut to 90 IN-Lbs as specified on page #53 of the Fuselage Manuel I can hardly rotate the tube. Mitch suggested making a shim from scrap the same thickness of the outboard leading edge skins, about .016" thickness for one side of the blocks. Cutout scraps from the landing light trimmings from the wing build should work. I'll let you know how that works when I get back to it.

I wondering if the specified 90 IN-Lbs torque is correct or has there been a change. I noticed at 70 IN-Lbs the tube rotated nicely. Any comments? As things change and sometimes don't get posted to the manual it's worth asking.

Thanks

Jim Morrical

Thanks Guys. I did talk to Mitch today (before the game started). What a guy....Mitch! Called me twice on a Sunday to reply to an email I sent!

Anyway, he said something must be going on with these back masts because they never had problems before and now there are several that have had problems (you probably being one Jim I guess). He told me to use a heat gun and try to heat it up to around 250 where the Loctite should turn loose. I did and it won't budge. Guess I'll end up cutting the torque tube and pulling it all apart. Will probably have to get a new rear mast because this sucker isn't coming off.

It fit tight but I could remove and install it OK before adding the Loctite and doing the permanent installation. All holes demurred and I even lightly sanded the inside before putting the Loctite on it. It went on fine right up until it just stopped about 3/16" from being completely on and then it just stopped.

Mitch said he will have to see what's going on in the factory. Something must have changed and they are making the rear mast a little too small. So it's something new to the kit that's causing it.

Before you put yours on Jim, (or anyone else doing a build) I'd check with Mitch. I'm pretty sure you are going to need to either sand it down or maybe he will have everyone send in their rear mast to be honed out a bit or something. The only thing about sanding is that getting it the same everyone is pretty much impossible so there would be tight spots and spots not so tight.

I just wonder what the difference will make if I just redrill the holes where it is now in the rear mast, install rivets and leave it. We are only talking 3/16" further distance. The distance between the 2 mast holes is suppose to be 30" and where mine stuck, it makes it 30-3/16". The rod that connects the 2 masts then would essentially split that difference between the front and rear control sticks which I guess would only make each stick about 3/32" off at the top bolt hold of the mast. Not much but I just don't know what, if anything, that would affect. Obviously, it would change the angle at the top of each control stick making the distance between the very tops of each control stick a little greater but I wouldn't think too much.

Any opinions?

thanks

[jmorrical]

Thanks Daveemby. That would be great.

Yes, ask him about the tube, masts and bushings diameter and fit. Have you seen the Service Bulletin - SB 00015 Rev C Effective date: Sept 13, 2011 requiring some serial numbers to check for torque tube to mast tightness?

I wonder what changes were made on later serial numbers to correct for this SB?

When I first played with the masts and tube on a level surface I notices the fit was very tight. Any side force on the mast while trying to slide it on or off just locked it up. And when you are working it thru the floor it is hard to line the parts up and keep them from binding. And you simply can't put the same amount of force on the parts when they are in place on the floor.

Also, I noticed on the bushings there were markings that I didn't pay much attention to the first time I put it together. Now I notice the "hieroglyphics" seem to have some order, so I wonder if the bushings are a matched set some how? Or can they simply be paired together in any order. Ask that too if you would please.

I wonder if that 90 IN-Lbs torque is still the correct torque for those bushings. I still think on my install there is way too much force required to rotate the mast in the lubricated bushings. This suggests something is not sized correctly. I haven't installed a shim Mitch suggested however. At 70 IN-Lbs torque the tube rotated with a reasonable force.


Jim Morrical

[Pete D]

Thanks Daveemby. That would be great.



I wonder what changes were made on later serial numbers to correct for this SB?


Jim Morrical

Later S/N a/c have a thicker wall torque tube and more rivets. The SB kit includes both of those upgrades.

[Daveembry]

Later S/N a/c have a thicker wall torque tube and more rivets. The SB kit includes both of those upgrades.

Thanks. So no change to the diameter of the TT? Mine is 1.498". I just torqued my front bearings to the 90 ft lbs and it seems to be just right......not too tight at all. I haven't done the rear yet as I'm waiting to see what to do with the stuck rear mast. But, it doesn't seem to be a problem with front bearing tightness.

[Mark Albery]

When I had the same issue, I measured the torque tube with digital caliper at 1.505".

I don't know what the manufacturing tolerance is on these tubes, but it suggested to me that they have got a batch of oversize tube.
I persevered with the wet emery starting with medium and finally fine grade.

I still needed to shim the bearing blocks. They were marked as matched pairs and I used a single thickness of UHMW tape as the shim.

[jmorrical]

Pete,

With the thicker tube did the CherryMax rivet HDW-CR3213-5-3 that is shown called for in diagrams change.

When I went to the Tote to find rivets for the aft mast I found a couple ...5-4s or 5-5s (Don't know what they are) in the section of a box marked as HDW-CR3213-5-3.

When these things happen I have learned to get suspicious.

Just askin'

Jim Morrical

[Daveembry]

Pete,

With the thicker tube did the CherryMax rivet HDW-CR3213-5-3 that is shown called for in diagrams change.

When I went to the Tote to find rivets for the aft mast I found a couple ...5-4s or 5-5s (Don't know what they are) in the section of a box marked as HDW-CR3213-5-3.

When these things happen I have learned to get suspicious.

Just askin'

Jim Morrical

My rivets fit fine and they were in the skinpac and not in the totes. I had to cut my torque tube to remove the rear mast. Mitch said tolerance on tube is 1.50" + .005. The inside diameter of the front and rear mast is exactly he same but it sounds like the rear masts have been too tight and fronts ok?


Mitch is revising the manual to say to use 320 sandpaper and use as necessary on the tube to allow the masts to slide on and off.

[jmorrical]

I am ready to start covering the fuselage in a few days...Carbon Cub EX. Long ago I had to leave finalizing the torque of the rear torque tube block for another day. I heard about the manufacturing tolerance concerns with tubes further back in this thread. I would like to get it done.

IMG_0955.jpg

Totally frustrated and still don't know how to get past this. I thought my torque wrench was out of calibration. It's not. The stiffener was cut up for the number of times I have taken it apart and torqued it down again. I ordered a new stiffer, new hardware thinking I had over torqued it all.

When the bolts holding the stiffener and torque tube blocks are torqued to 90 in-lbs the control is simply bound up. Even with the control stick in place the force required to overcome the friction of the blocks in my estimation is way to much. I have sanded the diameter of the blocks some and even added a 0.016 inch shim on both sides between the blocks. The torque tube is still bound up.

Should I try to sand the blocks more aggressively? I can't get the bottom block out from under the torque tube so that one is difficult to sand. If I sand too much off the top block I worry I am simply putting the blocks out of round.

Should I keep shimming until I get the stick freed up to my liking?

[Daveembry]

Hi Jim,

Check out Post #44 here http://forum.cubcrafters.com/showthr...2096#post22096

This pertains to the EX3 but for your situations, it's essentially the same. I describe in there the problem and solutions. If you already have it all installed, just loosen the bolts from the bottom where the belly pan will go and then cut up a soft drink/beer can and make some shims and slip them between the blocks until it works. Pretty easy to do. I'm not so sure why 90 in lbs is so important either as long as at least 1 thread and not more than 3 are showing through the lock nut.

I am ready to start covering the fuselage in a few days...Carbon Cub EX. Long ago I had to leave finalizing the torque of the rear torque tube block for another day. I heard about the manufacturing tolerance concerns with tubes further back in this thread. I would like to get it done.

IMG_0955.jpg

Totally frustrated and still don't know how to get past this. I thought my torque wrench was out of calibration. It's not. The stiffener was cut up for the number of times I have taken it apart and torqued it down again. I ordered a new stiffer, new hardware thinking I had over torqued it all.

When the bolts holding the stiffener and torque tube blocks are torqued to 90 in-lbs the control is simply bound up. Even with the control stick in place the force required to overcome the friction of the blocks in my estimation is way to much. I have sanded the diameter of the blocks some and even added a 0.016 inch shim on both sides between the blocks. The torque tube is still bound up.

Should I try to sand the blocks more aggressively? I can't get the bottom block out from under the torque tube so that one is difficult to sand. If I sand too much off the top block I worry I am simply putting the blocks out of round.

Should I keep shimming until I get the stick freed up to my liking?