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Cabin Door Hinges

jrichards

jrichards

Sponsor
Supporting Member
Sponsor
South Burlington, VT
Aircraft Year
1978 580
Aircraft Type
Super Commander
Reg Number
N555LP
Serial Number
14405
Hi All,

Anyone want to join a run of cabin door hinges?

We have previously engineered the basic replacement hinge blanks, and have personalized and heat treated a few of the 43722-3 (lower forward). Now comes another owner who needs the lower aft so we are about to run through the process again.

The process involves machining, then heat treating, then machining, plus priming, etc so the bigger lot of hinges we process, the cheaper for everyone. Just thought I would check and see if any of you with worn/bent hinges would like to join a run at this time.

Certification is by included Form 8110-3.

We include the 4th hole in the aft half, the improved design that prevents wind and racking from bending the door half of the hinge, thus the installation is improved.

Jim
 
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Re: Cabin Door Hinges

Jim

Would be nice to have a spare set laying around. Any idea what the cost will be?
 
Re: Cabin Door Hinges

Jim ... maybe if you could project ...if
10 sets ... the price is $X
25 sets .... the price is $Y
50 sets ...
100 sets ...

That would help many determine whether to jump in for a spare set
 
Interested. Will include the hinge pins also?
 
Re: Cabin Door Hinges

Dear Jim,

I would be interested in a set.

Thank you,

Pete
 
Re: Cabin Door Hinges

I would as well. I believe a combination of an old hinge and incorrect door seal is causing a closing issue on the pilot side. What did Scott say on the other post "count me in"

Dan
 
Jim I would also like a set reasonable cost determining factor.
 
Re: Cabin Door Hinges

Me too.

Thanks Jim
 
Re: Cabin Door Hinges

I'm interested.
 
Re: Cabin Door Hinges

Hi All,

Here's some additional information...

CPAC was selling old CAC stock for $225 per hinge half till they ran out.

The main costs on these are the CNC and the heat treat. We are doing some optimizations on our CNC programming at the moment. The best way to reduce the cost of heat treating is to run a larger batch.

I have attached a pic of the lower forward half we did last year, and of the additional blanks we ran at that time. Richard Rolland funded a major offset of the initial engineering, and will need to be factored in for some recoup. And Don McCosh will need coverage for the 8110's since I don't expect running these through for a PMA at this time.

For thinking purposes, I don't think I can match the 20-year old CAC cost unless we can get the top end of Scot's matrix at 100 pcs ordered.

A full set for one airplane is 8 halves. The most often bent are the 4 door halves when not the 4-screw type and never altered to add the 4th screw. The most often worn are the 4 pilot's door halves because they get the most use.

More later. Thanks for all your interest.

Jim
 

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Re: Cabin Door Hinges

I'd be in for a set of of 2... maybe more. I know for a fact I have a crack and a bend on pilots lower door side half and if I look real hard I may find another one that needs to be replaced.
 
Re: Cabin Door Hinges

Hi All,

We are busy on the cabin door hinge project, designing some CNC fixturing to reduce the cost of manufacturing while holding close tolerances.

I have attached a pic of the typical bent hinge. When the hinge is bent, the attack on the airplane progresses to chafing of the door jambs, even to the point of perforating the jambs. If there is anything you might like to avoid, it would be having to replace your door jambs. Also, the repeated flexing of the hinge will eventually crack it.

Also included is a pic of the 4th screw that I have mentioned. This late-model design change was too eliminate the susceptibility of the hinges to bend. The applies only to the door halves of the hinges. We will offer both 3-hole and 4-hole flavors to be used as follows:

3-Holes: For aircraft that had a 4th screw installed previously by field alteration. The 4th hole will be match drilled at time of installation of the new hinge to match the 4th hole already in your door.

4-Holes: To be used on aircraft that have never had a 4th screw, and to replace worn 4-hole hinges that were factory installed.

By next week, we should have some solid numbers on cost and I will post again to determine how many of you would like to participate in the pre-buy. At that point, I'll only be able to wait a few days before closing out the pre-buy opportunity and proceeding with manufacturing because we have two aircraft AOG waiting on hinges.

Please post here if you want us to remind you when the pre-buy is closing. The on-going regular price will be significantly higher.

Thanks,
Jim
 

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Re: Cabin Door Hinges

If done carefully the original hinges can be bent back without even scratching the paint, and if you install the gas spring door stays they will never bend again. It might be cheaper than replacing the hinges, paint etc.

Adding the 4th screw will save the new hinge from bending, but you risk bending the door. This, of course, is a much bigger problem (and more expensive). There are many Commanders flying with doors that have suffered this fate.

The factory door stays place too much leverage against the lower hinge, so as long as you continue to use them you are at risk of bending something. The gas spring door stays eliminate this risk by reducing the leverage against the lower hinge by more than 50%. The gas springs are not only cool, they are functional.

This is not an effort to sell a product. I have plenty of other things to do than to sell gas springs. I'm just trying to save those of you that don't already have them from the aggravation and expense of bent airplane parts.
 
Re: Cabin Door Hinges

Hi Carl,

Your gas spring kits are very nice and a product I recommend regularly.

Agreed, the gas springs do help reduce the bending moment on the hinges. That reduction probably falls in the 20-30% range since most of the door is still aft of the average gas spring attach points.

In my mind, the best overall door and jamb protection is having gas springs, straight hinges, and 4th screws.

Jim
 
Re: Cabin Door Hinges

jrichards said:
That reduction probably falls in the 20-30% range since most of the door is still aft of the average gas spring attach points.
Jim
Click to expand...


It is more than that. I have the exact amount in the DER report we submitted to the FAA. I'll look it up and post it for you. The fact that most of the door is still aft of the gas spring attach point is irrelevant. The load on the hinge increases as you move the attachment point closer to the hinge, but the increase is exponential not linear.

jrichards said:
In my mind, the best overall door and jamb protection is having gas springs, straight hinges, and 4th screws.

Jim
Click to expand...

I agree.
 
Re: Cabin Door Hinges

According to the DER report:

Just under 50% reduction in load on the hinge for the early models, over 50% for the late models, and 15% less load on the attachment points.
 
Re: Cabin Door Hinges

Hi Carl,

Sounds like a truly fun vector analysis, good work!

My own conclusion was reached empirically by comparing the bending deflection on the hinge when applying the same force to the door for both configurations: OEM strap, and gas shock. The shocks help a lot, and are affordable insurance for one of the best parts of our airplanes: our great doors!

Since you and I have loaded up the thread, I want to refer everyone back to my posting early today asking for those who may want to replace their bent or worn hinges to post here so we know who to remind when we have the cost data next week.

Jim
 
Re: Cabin Door Hinges

Still interested in having a spare set on the shelf, if the price is right.
 
Re: Cabin Door Hinges

Ditto Joel.... I could use a set. I have a hinge that was slightly bent (and is now showing a slight crack) This occurred before I installed the gas door struts which are wonderful.... I'm just getting to the weather here in TX where taxiing with the door open is a must and the gas struts make it much easier and less stressful on the door.
 
Re: Cabin Door Hinges

Carl -
I LOVE my gas struts! But long taxiing in hot weather like I had today is a PITA. Have to keep one hand on the armrest to prevent the door from opening completely.

I've even given some thought to inventing some type of "door holder" to keep the door open a couple of inches while taxiing.

k
 
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