Upper Door Hinge, is yours Straight or Bent?

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Bruce Fenstermacher
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Upper Door Hinge, is yours Straight or Bent?

Post by Bruce Fenstermacher »

As some might know good upper door hinges are getting harder to find. There is no current supplier. Some time ago McFarlane started research into producing these hinges. They had to put the project on the back burner for a bit but recently have gotten back to work on it. We have been contacted by Dan, a McFarlane engineer to ask a question about an observation they've had of the samples they have collected.

It seems that some of their samples are straight but more than enough are bent to question how the hinge should be. Here is a sample of a bent hinge from Dan:
Sample of a bent upper door hinge
Sample of a bent upper door hinge
image001 (1).jpg (8.18 KiB) Viewed 16281 times
Dan would like to canvas our members to see how many door hinges might be bent vs straight. He would also like some pictures of samples found bent with a straight edge in the image so they might be able to gauge how bent the hinge is.

I realize very few if any of us have door hinges that are not attached to a door as in Dan's picture. But I thought each of us could go out to each of our doors and look at our hinges. Please report back if you feel your hinges are straight or bent. If you feel they are bent, try to take an on edge (like Dan's photo) image with a straight edge and post it for Dan. Also if you find yours are bent, you might comment whether you thing the bend help or harms your doors fit in the fuselage.

Hopefully we can assist Dan and McFarlane to produce the best hinge all of us might use.
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johneeb
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by johneeb »

Bruce,
My hinges would not be good references as while doing the restoration on my 170 we pie shape cut and welded the hinge back bones in order to bend them to look like the one in your picture. We did that modification to the hinges to get the leading edge of the doors faired into the door opening. I have always been happy we made that modification as it has helped the doors seal better and cut down on the wind noise in the cockpit (although that could also be a function of old ears).
John E. Barrett
aka. Johneb

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ghostflyer
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by ghostflyer »

Just checked my upper hinges and found them to be flat ,on both doors
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c170b53
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by c170b53 »

This should be interesting, I've often wondered about this condition:
Bent x 2.
I did re-skin one door, I know that the upper hinge forward rivets can be troublesome to get at as I believe (from memory) there's an internal diagonal stiffener on the inside. I tried to straighten one thinking it should be straight but a hinge is made up of two parts (as can be seen in Bruce's sample), riveted together which makes the task that much harder. I also realized on my plane that making the hinge straight caused the door's leading edge to have a positive step, allowing airflow into the cabin at the hinge point.
Edit I think John came to the same conclusion, Sorry John I missed reading that
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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GAHorn
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by GAHorn »

c170b53 wrote:This should be interesting, I've often wondered about this condition:
Bent x 2.
I did re-skin one door, I know that the upper hinge forward rivets can be troublesome to get at as I believe (from memory) there's an internal diagonal stiffener on the inside. I tried to straighten one thinking it should be straight but a hinge is made up of two parts (as can be seen in Bruce's sample), riveted together which makes the task that much harder. I also realized on my plane that making the hinge straight caused the door's leading edge to have a positive step, allowing airflow into the cabin at the hinge point.
Edit I think John came to the same conclusion, Sorry John I missed reading that
Note: this is Dan’s/McFarlanes sample illustrated.

The bend is likely caused by the stamping-process and the backing=piece is intended to stiffen the completed hinge. This is the conclusion of 4 Members I have contacted. I am still awaiting our “master” in Mena’s response.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by hilltop170 »

The upper hinges on my 1958 C-180 are bent as shown in the picture in the first post. Since some upper door side hinges are straight and some are bent, maybe it depends on the vintage of the hinge? If early ones are straight, maybe Cessna saw they needed to be bent in order to flush the leading edge of the door to the fuselage? Just a thought.

My observation is the door side of the hinge has to overlap two layers of structure in addition to the fuselage skin on the door post, 1- the boot cowl skin and 2- the fuselage side of the hinge. So a straight door-side hinge will cause the door skin to stand proud of the door post skin if not bent. The bend in the hinge causes the door skin to be flush with the door post skin.

McFarlane needs to make replacement hinge pins as well, both sizes, for something less than the $25/each F.A.Dodge gets for them.

I have had to repair the upper hinges on both sides of the 180 thru the years. I found 7mm diameter steel brake line tubing to be a match for replacing the hinge pivot. Note in the picture the lower leg of the pivot was extended to the same length as the upper leg of the pivot. Originally the lower leg is about half as long as the upper leg and is usually where it breaks.

It's also obvious the paint shop did not remove the hinge fairing when the plane was repainted in 1991. :evil:
Upper door hinge repair
Upper door hinge repair
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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DaveF
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by DaveF »

Both of my door hinges have "the bend". It's bent against the force of closing, so I've always assumed it was intentional, to keep pressure on the hinge and latch so they don't vibrate in flight. The folded steel design of the hinge looks like a spring. To me it seems unlikely that a bend of that size could simply be a manufacturing flaw.
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GAHorn
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by GAHorn »

I want to include the exact wording of Dan’s email to me which initiated this discussion topi and which included the picture previously posted in Bruce’s post:

From: Dan Hartness
Sent: Tuesday, November 19, 2019 9:33 AM
To: 'George Horn' <gahorn146ys hotmail.com>
Subject: Cessna 170 Cabin Door Hinges

George,

I wanted to drop you a line to let you know that our PMA Cessna 170 cabin door hinges project is nearing completion. We had to set it aside for a while, hence the delay since you and I last communicated. I do have a topic I’m hoping you and the International 170 Association can help with.
We’ve noticed a trend with the upper aft hinge halves where the stiffener is bent outwards rather than simply being straight. I’ve included an example photo below. This bend is right over the door‑doorpost gap and has the effect of slightly angling the door so that the leading edge of the door sits more flush.
Would you and some of your members be willing and able to check their upper aft door hinge halves for the presence or absence of this bend? On-edge photos like the one below, with straight edges for reference would be most helpful, and by the end of this week would be even better.”


The reason I wanted to include the exact wording is because I believe there is some confusion on what is being considered.
The pressed-steel outer-portion of the hinge-assembly is “bent” or “curved” in the depiction (the “humped” outer portion which has been DETATCHED from it’s inner-stiffener) is what I believe Dan Hartness is asking about. There appear to be some respondents that are addressing the “pin-hole-hinge” area of the hinge assy. There is a difference!
McFarlane is attempting to create a duplicate of the Cessna assembly. The manipulation of the pin-hinge area is adjustable by the installer to accommodate door fitment. If I read Dan’s query correctly, that is NOT what he is asking.
Since few of our Members have removed the assembly from their doors and removed the rivets or opened the hinge-body from it’s stiffener, it seems to me that few of us can comment on this without doing so (disassembling the outer/inner hinge laminate.) PLease be careful how you address your answers to be specific as to what “bend” you are addressing. Thank you.

BTW, here is Del Lehmann’s response:



---------- Forwarded message ----------
From: Del Lehmann <del mountainairframe.com>
Date: Dec 9, 2019 12:04 PM
Subject: RE: RE: Cessna 170 Cabin Door Hinges
To: 'George Horn' <gahorn146ys hotmail.com>
Cc:

Hi George,
I have seen them perfectly straight, and with varying degrees of “bend”. Not sure if the bend was factory “adjustment”, a field adjustment, or indicative of some type of damage.
I only have two B models in the hangar right now. Charlie Beyer’s are both perfectly straight, and the doors fit really well. The other plane pilot door hinge is perfectly straight, however the leading edge of the door protrudes about a 1/16th of an inch (it would benefit with a bent hinge), and the co-pilot hinge has a slight bend; approx. half the bend that the hinge in the below email traffic shows, and it fits very well.

I know this doesn’t offer much of sample, and I can only suspect they were originally made straight, then adjusted for ideal door fitment (beat to fit, paint to match)

Del Lehmann
Mountain Airframe, LLC.
102 Aviation Lane
Mena, AR 71953
(479) 437-333three
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
hilltop170
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by hilltop170 »

I checked my 1951 C-170A upper door hinges today. Both sides are identical. Both door leading edges are flush with the fuselage and do not stand proud.

Both R and L top door hinges have the bend in the door side (aft) hinge. I measured the angle of the bend with my digital angle-o-meter, aka iPhone compass, at 3° on both sides. The bend is located between 4 and 4-1/2” aft of the hinge pin centerline, adjacent to the leading edge of the doorframe. Holding a straightedge across the hinges as requested touching the hinge at both ends, there is a gap of about 3/16” right at the bend.
3/16” gap right at the bend.
3/16” gap right at the bend.
Another interesting observation on my 170A is both doorposts appear to angle outboard to the front, actually they are perpendicular to the axis of the landing gear, which makes sense. This in itself would cause the top hinge arms to need to be bent. This is evident in the picture below.
Looking down at the top hinge showing the bend and the doorpost angled outboard to the front.
Looking down at the top hinge showing the bend and the doorpost angled outboard to the front.
Looking forward across the top of the top hinge showing the bend and the doorpost angled outboard to the front.
Looking forward across the top of the top hinge showing the bend and the doorpost angled outboard to the front.
Last edited by hilltop170 on Thu Dec 12, 2019 2:59 pm, edited 2 times in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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Bruce Fenstermacher
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by Bruce Fenstermacher »

Excellent photos Richard. Exactly what I understand Dan is looking for.

Can't say my current 170A is like yours Richard. But I definitely remember my first looking exactly like it. And I definitely remember trying to bend my door hinge like yours to remove the the air scoop (gap) formed at the front of the door.
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edbooth
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by edbooth »

My 1953 B model has the same type bend that Richards has.
Ed Booth, 170-B and RV-7 Driver
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c170b53
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by c170b53 »

Ok, sounds like there might be some consensus out there. I think that a few of us thought we could simply straighten out the bend until we looked closely at the hinge build. Since the parts are riveted together, unless the rivets have joggled (flush riveted on the forwards backside), it’s hard to imagine that the bend has occurred on its own without some indication of rivet distress. Hummm...
I’d just like to mention,now that we are focusing at this area, it’s steel component on aluminum. I suspect paint prep in this area must be carried out very carefully, otherwise seeds, trace amounts of Fe2O3 left behind in the crease between hinge / skin, will spur growth under the paint. Bubbling painting on a plane is never a good sign.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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DaveF
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by DaveF »

Sounds like it could be another circular or slotted holes? topic?

There's a 0511106-19 hinge on ebay right now that looks flat. It's off of a 170A.
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Bruce Fenstermacher
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by Bruce Fenstermacher »

DaveF wrote:Sounds like it could be another circular or slotted holes? topic?

There's a 0511106-19 hinge on ebay right now that looks flat. It's off of a 170A.
Dave, I had the same thought. Not sure if they would do it make both but Dan asked, bent, flat or both styles.
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hilltop170
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Re: Upper Door Hinge, is yours Straight or Bent?

Post by hilltop170 »

They might as well sell both straight and bent. They will all be straight at first when they are made. The bend is an additional manufacturing process prior to riveting the backing strip.

If I was McFarlane, I would have a bin full of finished straight hinge pieces and a bin full of undrilled backing strips. Then as orders come in I would make them to order, either assemble straight or bend them and rivet.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
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