Trim crank steel roll pins, sizes?

[Rookie]

Today while flying my last leg home, I found my trim crank to be non-functional. After an uneventful flight pushing the stick the whole way, I talked to a Super Cub pilot who correctly diagnosed the symptoms as the results of the steel pin that secures the trim crank shaft to the pully assembly having gone missing. I haven't found it yet, but he was right, that's why the crank was spinning freely.

To get the crank off, I had to punch out one roll pin. I then removed the cover plate, and could see that the shaft and the pully are independent. I can see the grooves radially from the shaft hole to allow the installation of the steel pin. I have the pin I removed for the crank, but the drawing I have (from a L-21A erection manual) doesn't show the sizes of the pins. Are they both the same diameter? The drawing makes it look like the one I have is shorter, what is the length of the one I'm missing? What is the best way to get a proper replacement pin?

Thanks!

 

[Rookie]

Now with a picture

Hmm, no response. Maybe it will help if I include a picture:

I have the pin shown as #9, but I'm missing #10. Can anyone tell me if these pins are the same diameter? I can go get an assortment, but it would be helpful if I had some basic parameters.

Also, what about the spring shown as #6? I think mine is missing, should I care?

Thanks!

 

[kase]

Item # 10 in the drawing is pn 81761-004, it is 7/8 X 1/8

 

[Steve Pierce]

That spring pushes the chrome escutcheon plate out from the cover plate.

Steve

 

[Rookie]

Now that I look closer, I'm realizing that I don't have exactly the same crank, mine is more like a car window crank, and the escutcheon plate is attached to the crank shaft. (Escutcheon; strange word, I had to go look it up, is that the strangest name for a part of a Cub?)

I guess I should stop trying to use the L-21A Erection Manual I have, and ante up for a proper 1979 PA-18 parts manual. Or that CD.

 

[PA12driver]

Rookie, The pin can be made out of a piece of 1/8in welding rod just fine! cost (nothing) the pulley has a slotted area on each side of center hole to allow for the pin to be inserted in (tapped in-press fit) and to be then extended out each side but below the surface of the pulley so it will turn unabstructed. I had the same problem (not uncommon) the original pins I believe were Brass) I use 6010 welding rod and make a slight bend in it with a slight point filed on it so as to start it in the hole. Line up the pulley and the shaft and start tappiing with a punch- if it is too long or short you can keep doing it till you get it right-(cost nothing)

Most cub trim handles have been replaced with a bigger Knobbed automotive style one.

Hope this helps

Tim

 

[Rookie]

Yes, that does help. Thanks!

It wasn't fun having to fly without adjusting trim; I could even see it being a problem on landing if one had the misfortune to have the trim set well off optimal for an approach glide when the pin goes missing, and the crank won't crank. This happened to me on my fourth leg of a good day of flying, and before it happened, there was a clue. I felt a small point of resistance on one part of the revolution of the crank, in about the same spot. My guess is that it was the soon to be missing pin rubbing on some part of the crank mechanism, before it fell completely out. If I feel that again, some resistance on some part of the crank, I'll make a point of investigating it before I launch again.

 

[PA12driver]

Rookie, the same happened to me! That is how I learned as well. I actually watched the pin fall to the floor and disappear into the belly, (never to be found again till recover time)

Tim

 

[CubCouper]

While we're on the subject with picture in hand, the indicator screw (#5) on my cub occasionally disappears behind the slot. I learned how to disassemble this contraption and make it tight, then I learn how to fish the screw back out with a piece of safety wire (which I now keep conveniently wrapped around the screwhead to prevent further trouble.

Question is: with the indicator missing, can you crank the trim too far? Does the trim cable just slip once the stabilizer has reached it max deviation? Would this break something (like the indicator cable)?

 

[Steve Pierce]

The indicator is a piece of saftey wire going from the leading edge of the stabilizer to the screw you are talking about to a spring just forward of the indicator screw to put a little tension on the wire. The trim cable is a continous loop one piece cable. If you kept cranking as guess after a while it would wear out the cable and probably the pulleys. You never want to get oil on the cable or the pulleys cause it will just spin. An old timer showed me how to make these one piece cables. It's pretty neat but you prick your fingers with the strands of cable. As far as the indicator goes, all the ones I have seen have a small rivet as an indicator. I too got tired of fishing it out from behind the trim plate and took a small nylon washer like you use to keep cowling screws from rubbing through the sheet metal and cut one side of it, then thread it around the head of the indictor screw (rivet). No you have a larger diameter and it won't rub the hole bigger.

Steve

 

[SuperCub MD]

When the aluminum indicator rivet wears out, I drill it out and replace it with a stainless steel sheet metal screw. Then you can install/remove the screw when installing/removing the cover plate instead of bending it around the rivet.

 

[Lance]

Is there any reason why you can't just go without the indicator?

My wire broke, so I took it out. Works just fine. You just have to count the turns of the crank!

 

[PA12driver]

My VSI, quit and I took it out!, I can't tell you when I last looked at the indicator on my trim. I usually fly with about the same weight, the trim is within a 1/2 turn of the same at cruise and when I pull full flap for landing I roll in 6 turns of forward trim gives me the maximum stabilizer for most effective flare? Works for me. A guy asked me what airspeed I flew the approach at and I told him I hadn't a clue, I just feel the plane and keep my head out the window! You tend to hit trees, rocks, logs and stuff if you spend your time looking at the panel, trim, brakes, GPS and all that stuff.

Maybe I am wrong but if you have a better way please teach me I am all ears???

Tim

 

[Lance]

Just out of curiosity, do you or ya'll have to roll full up trim to get the bird to flare descent in a power off landing? If I am descending with no power and slow, if it isn't trimmed full up, then it will not fully flare. Its no problem, I was just wondering of others ideas on the matter.

You also have to be careful in a go around because if the trim isn't rolled off of "full up" the plane, or at least mine, will out climb the down elavator authority resulting in a loss of speed.

I have flown other SC's and they seem to be relatively the same.

Any input?

 

[Cubus Maximus]

trim

What you brought up is something we think killed a couple guys in St. Paul a couple years ago. Student and instructor at the U&M Ag strip doing touch and go's. I believe the trim was found in the full up position and it was a classic departure stall. Jim Drometer would know more about it.

My old 18 never had a problem flaring at almost any trim setting, but the PA-12 I've been flying lately needs way-back trim power off or it's a wheel landing every time.

Brad

 

[kase]

When I fly solo I always land with 2 turns of trim nose up full flaps and carry some power. If not I cant get the tail down. Go arounds are not a problem. My battery is under the front seat so my cg maybe farther forward than some cubs.

 

[SuperCub MD]

This is intersting, some Cubs seem out of balance, and some are perfect. My EWCG, with oil in the engine, ready to gas up, load and fly is 13.5" aft of LE. This leaves it comfortably in the forward range when empty, and since everything is loaded aft of the CG, as I load, the CG slids back through the range. Even loaded to the hilt with full winter camping gear in the extended baggage, I've never gone out of aft CG. Trim is set for load, and I never have to retrim for landing, adding flaps when slow retrims perfectly, never, ever run out of elevator. But I have flown Cubs that do not have the same balance. There are LOTS of other factors that make the plane behave properly when slow, but I'm curious of what others EGCG is, and how their planes behave when slow. Anyone have their W&B handy to compare?

 

[kase]

Wheels EWCG 11.27

Hyd skis EWCG up 9.9 down 10.26

I have Hawker batt under front seat. B&C starter and alt. Atlee ext baggage, 82 in prop. Like you say when you load the plane it is good. I put a 180 lbs guy in the 3 rd seat and was still in limits. My PA11 ewcg was 16.1. As far as flying slow I havent noticed any bad habits, it seems to land just as slow as any other round tip cub. I also have micro vgs. When im really trying to land slow I may use 3-4 turns of nose up trim when im alone. With 2 people or gear I generaly dont use any trim.

 

[Lawn Dart]

Empty (no oil) 1,042 @ 11.61
8 Qts oil..........1,057 @ 10.93 (normal empty weight)
36 Gals fuel.....1,273 @ 13.15
My big butt .....1,458 @ 12.88
292 Lb Pass....1,750 @ 16.90
OR
242 Lb Pass...1,700 @ 16.31
50 Lbs bags...1,750 @ 17.47