Retractable Step Servo Parts Breakdown?

[RLCarter]

Ok, I've searched MS for options for replacing the servo seal, boot, diaphram or what you would like to call it. It looks like Brittain no longer sells the rebuild kit and only offers off the self rebuilds or send yours in for repair, $170.00, the price range is fine, the problem is Brittian has an issue with the mold or the material being used not sure which but from what I can gather it is a 4 yr old problem that has no priority. I have removed the servo assembly and taken it apart to get the measurements on the boot and machine my own mold. Does anyone have a parts diagram of the servo? It seems odd that the only thing that holds the piston(lower cup with pulley) to the cylinder(upper part where the vac line connect)is the rubber boot, if the boot becomes separated the lower portion would fall into the belly of the tail section and possibly jam the control tubes directly under it, or is mine missing a saftey chain, cable or something.

[Hank]

Don't know about the step servo, but the boots on flight control servos are held on using o-rings like rubber bands, then fold the boot back over it and tape it down with 3M #33 electrical tape. That is the procedure that Brittain gave me before I found one with a tear and sent it in to them.

[RLCarter]

Hank,

Same on the step, was just wondering if there is suppose to be any saftey chain or cable between the cylinder and the piston.

[carusoam]

Without pulling out the drawing...

The top is connected to the airframe.

The bottom is connected to the step, which is captured.

I can't picture what is going to fall out and jam controls...

Definitely get the drawings that are available in the parts and MMs.

It would make wise research prior to building a mold.

Best regards,

-a-

[RLCarter]

-a-,

You say the bottom is "captured" but how? The Parts and MM that I have do not show a breakdown of the servo it self. My servo boot was in really bad shape there was only about 3/4" of rubber material holding the bottom to the top, if the boot tears completely in half(top to bottom) the bottom piston, pulley and cable will fall and did fall into the control tubes. As far as the wise research what are you trying to warn me about?

[carusoam]

RL,

I was merely suggesting to use the drawings available in the parts and MM.

If you have been there already, there isn't much. But it is better to proceed with that data in hand.

My 65C had worn out every system possible. The step and servo seemed to keep running with an annual cleaning. The other parts of the wing leveler system were in-op in my plane from the day I bought it.

I was probably blissfully unaware that the parts could separate.

On the other hand, I had strong faith that the annual maintenance would keep things from progressing that far in one year.

I ended up leaning towards a much more expensive solution to the problem(s) you are describing.

Best regards,

-a-

[RLCarter]

The mold or actually a buck is all but done, this is a temp repair until Brittian decides to make another batch, a linear actuator might be a project in the future if the paperwork doesn't get too bad

[carusoam]

We have an MS guy on board that is familiar with paper work process. He is building a cowl currently.

If you are familiar with linear actuators of the 12 volt variety, see if you can select one the meets the requirement.

Post it up, get some responses...

Stronger, lighter, safer, available, and or cost effective would be nice...

Best regards,

-a-

[HRM]

Check this link, vacuum actuators and membranes--might be a solution there.

 

One reason vacuum was used for this was the fact that a linear actuator back then either did not exist or weighed a ton and the aircraft was already committed to vacuum as a power source.

[N601RX]

Some of the Britain actuators use a piece of cord with a ring terminal crimped on each end. It is internal to the actuator and connects under the head of the bolt on each end of the servo. 

The "Rubber Boot"  as we call it is better know as a rolling diaphragm. Many stock sizes are available here.  See page 15  http://www.marshbellofram.com/belgas/files/2012/05/design_manual.pdf

[RLCarter]

The paper work isn't really that hard, it's more of a hide and wait thing that drives me nuts. It's my understanding that Brittain owns the mold but farms out the actual manufacturing of the boot. Owner produced parts are legal, they just can't be sold, it's going to boil down to a material that is easily worked. The vacuum step is a very simple design, too bad the part that fails most often is also the hardest to duplicate

[Steve65E-NC]

The Marshbell reference is very interesting.  Can you provide any gridance on the most likely candidate for the step boot and its cost.

[RLCarter]

Some of the Britain actuators use a piece of cord with a ring terminal crimped on each end. It is internal to the actuator and connects under the head of the bolt on each end of the servo. 

The "Rubber Boot"  as we call it is better know as a rolling diaphragm. Many stock sizes are available here.  See page 15  http://www.marshbellofram.com/belgas/files/2012/05/design_manual.pdf

When I took mine apart that was the first thing I thought of, no evidence of ever having anything as a saftey strap. It will go back together with one.

[carusoam]

I looked up in the parts catalog.... Page 251.

The drawing does not mention a safety strap or any additional detail to indicate there is a way to keep the bottom half of the 'servo' from falling out. check with your mechanic for next steps...

I'm only a PP, not a mechanic.

Best regards,

-a-

[MyNameIsNobody]

Some of the Britain actuators use a piece of cord with a ring terminal crimped on each end. It is internal to the actuator and connects under the head of the bolt on each end of the servo. 

The "Rubber Boot"  as we call it is better know as a rolling diaphragm. Many stock sizes are available here.  See page 15  http://www.marshbellofram.com/belgas/files/2012/05/design_manual.pdf

Again, while "stock" diaphragms may be available the reason that Brittain can't produce them is because of the rubber on the certified unit no longer being available...They must jump through numerous regulatory hoops to "prove" that the new formulation works to certified standards. The "stock" units would not be "legal" in a certified plane, right?

Brittain was able to "get me a unit" when I had plane in for re-do on all PC servos and altitude hold install. Keep pestering them. Squeeky wheel...

[N601RX]

Here is a picture of the safety cord they are using to prevent the center part from falling out. The ends are a heavy duty electrica connector bent 90 deg. The length appears to be set so that it will tighten up just before the rubber pulls off.

[RLCarter]

Spoke with Brittain this morning, they say the delay is do to the mold being dropped and damaged by the people that manufacture the seal for them. Brittain has a trip planned out to California to see what they can work out. I would really be surprised if they sell 100 of the seals a year so it's not cost effective on such a low production run. My guess Brittian pays less than $20.00 per unit and it isn't worth the trouble for $2000.00 order. I know several guys in S. Tx. that do injection molding for the auto industry that might be willing to spit some out, I'll talk to them and give the Brittain's info if they are interested

[Rhumbline]

Spoke with Brittain this morning, they say the delay is do to the mold being dropped and damaged by the people that manufacture the seal for them. Brittain has a trip planned out to California to see what they can work out. I would really be surprised if they sell 100 of the seals a year so it's not cost effective on such a low production run. My guess Brittian pays less than $20.00 per unit and it isn't worth the trouble for $2000.00 order. I know several guys in S. Tx. that do injection molding for the auto industry that might be willing to spit some out, I'll talk to them and give the Brittain's info if they are interested

If not from Brittain themselves, I've heard that the retraction servo in a Mooney is the same component used elsewhere in Bonanzas and that those guys are gnawing for relief as well.  I have an ebay salvage servo sucking my step up at the moment but I'm guessing there are more than a few paying folks waiting for Brittain to get the mold issue ironed out.

[RLCarter]

First I've heard about Beech using the same servo, thought the step was tide into the landing gear on the older Bonanzas

[Rhumbline]

Going from memory here so take it for what it's worth, but I'm pretty sure it was someone at Brittain and the Beech uses it as a yaw damper or AP servo. In any event, no urgency has been demonstrated in the glacial pace of getting the new mold. Every time I've spoken with them, it's always another month or two. That's been going on for at least 1 1/2 years.

[RLCarter]

Going from memory here so take it for what it's worth, but I'm pretty sure it was someone at Brittain and the Beech uses it as a yaw damper or AP servo. In any event, no urgency has been demonstrated in the glacial pace of getting the new mold. Every time I've spoken with them, it's always another month or two. That's been going on for at least 1 1/2 years.

Looking at some of the post on MS it's more like 4 1/2 years. If it is a compound issue I would settle for a limited life seal of say 5 yrs if they would offer just the seal and have a local A&P sign it off with a parts cost of around $40.00 or so. I'll make one and see how it turns out, my mold is no way made for production but more of a once in a while type deal, rubber will require some trimming on the upper(open) end. With rapid machining available and a very simple mold as this one would be Brittain could have a new mold built for a couple grand and be back in business on this issue

[N601RX]

We used to make make a similar seal at a large Aerospace company I worked for.  We had a male mandrel that was turned slowly with a motor.  We had 3 fixed spray guns that sprayed a 2 part rubber like liquid onto the surface.  On the opposite side we a couple of heat lamps.  The process produced about 1 seal per hour. Some of the seals required a light cloth reinforcement in the center layer.  The material was very similar to the rubber on the servos and had something like a 40 year pack life.

[RLCarter]

We used to make make a similar seal at a large Aerospace company I worked for.  We had a male mandrel that was turned slowly with a motor.  We had 3 fixed spray guns that sprayed a 2 part rubber like liquid onto the surface.  On the opposite side we a couple of heat lamps.  The process produced about 1 seal per hour. Some of the seals required a light cloth reinforcement in the center layer.  The material was very similar to the rubber on the servos and had something like a 40 year pack life.

Going to use basically the same process, but hand layup

[Rhumbline]

Looking at some of the post on MS it's more like 4 1/2 years. If it is a compound issue I would settle for a limited life seal of say 5 yrs if they would offer just the seal and have a local A&P sign it off with a parts cost of around $40.00 or so. I'll make one and see how it turns out, my mold is no way made for production but more of a once in a while type deal, rubber will require some trimming on the upper(open) end. With rapid machining available and a very simple mold as this one would be Brittain could have a new mold built for a couple grand and be back in business on this issue

 

Merely relayed what I know on the topic for anyone interested.  My dilemma dates 1 1/2 years and I'm not in the practice of commenting on behalf of anyone else.  Sounds like you have the bull by the horns.  Build a better mousetrap and, well...you're a smart guy, you know the rest.

 

[Guest]

Part of the problem may well be too many CB's. "I'd be willing to buy one if only Brittain charged $X.XX" fill in your number.

Face it the market is very small and getting smaller every day, at some point it's just not worth it for them at the current retail price, maybe at something higher it's worth it.

Clarence