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front seat extension modification

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txgr
 txgr
Posts: 51
Trusted Member
Topic starter
 

A friend showed me the way the front seats attached to the frame on his 108. If I recall correctly, the rear seat supports/legs attach to a second tube, just 2-3 inches in front of another tube running port to starboard - two parallel cross supports very close together.

His idea was to see about placing another rear leg going from the rear of the front seat to the further aft cross-support tube on the frame. Then, you could lenghthen the seat track, possibly up to 3 or 4 inches.

For those of us with log legs (like him) or oversized bellies (like me) those inches could significantly improve the forward space and allow the yokes to better clear our legs.

I would really like to make this modification on my 108-3, but right now it is just an idea for his straight 108.

Obviously that would require FAA approval, but what kind of supporting documents would they want to approve something like that?

What do you think about the practicality of the idea?

What do you think about the practicality of getting FAA approval?

Any comments appreciated.
Thanks,
N637C

 
Posted : 05/03/2008 8:04 pm
Posts: 43
Eminent Member
 

We are in the process of redoing the upholstry in our 108-3 and had the option of setting it up for the seats to move back further at the expense of not being able to pull it up as close. There are tracks welded to the bottom of the seat frames that can be cut off and so long as both sides are moved forward and equal amount and possibly one or two notched drilled into the adjuster arm, you would have more leg / gut room. In our case, we opted to keep the stock locations for the frames we had to make up because the originals were not useable or repairable. If you just need gut room, you can either shorten the control yoke or use one from another airplane that is shorter. I've seen that done on a 108-3 using Bellanca yokes and very cool looking control wheels. Again, we elected to keep things stock because they suit us just fine.

 
Posted : 09/03/2008 12:34 am
txgr
 txgr
Posts: 51
Trusted Member
Topic starter
 

Thanks for the response.

While gut room is just a comfort issue, the long legs are more serious I think. With the seat adjusted all the way back, full deflection of the yoke requires overpowering my leg. With a kneeboard of any kind, full deflection is really impossible without lowering the leg by removing the foot from the rudder pedal. While I doubt I'll need full deflection, if I ever did I am suspecting I won't want to give up control of the rudder pedals.

I will send this to my friend. I think one of the issues was a concern about moving the seat back because of the location of where the rear supports attach to the frame - you would end up with a lot of weight behind the rear support. I am not in a place where I can look at it now. That is interesting though, and I will definitely look at that option.

I'm sure you'd still need a field approval, but what kind of supporting calculations or considerations would the FAA want?

I'll ask about your new interior in another post.

thanks again,
Brian
N637C

 
Posted : 09/03/2008 11:43 am
Posts: 5
Active Member
 

Anybody who has already come up with a way to move the pilot seat back a few inches or thinks they have a good way to do it, please post your information. I am six two and all legs. I fit in my 108-2 but it is close, and a few more inches of leg stretchout room would be a godsend. I will post any develpments I come up with. A few more inches, priceless.

 
Posted : 19/03/2008 7:27 pm
Posts: 16
Active Member
 

I have a fellow at work who is 6' 9", he would like a ride in my 108, I told him maybe if I took
out the copilot seat he could sit in the back and possibilty operate the controls ...
Blue Skies... Walt & 97440

 
Posted : 30/03/2008 11:01 am
truckerloyd
Posts: 57
Trusted Member
 

Man, I too would like information on this idea. We are currently in annual and the pilot seat has a broken frame and will have to do some welding along with the cross straps. Must have been "Godzilla" in this aircraft prior to our assignment. At this time, we are looking at a "few inches more" and are in discussion with our I.A. If we get a go ahead, I'll post what we did. May be a few weeks.

Lloyd

 
Posted : 19/05/2017 4:26 pm
truckerloyd
Posts: 57
Trusted Member
 

Found this link. Don't know if I have the knowledge to do this but maybe some of you might. I don't think we'll do this as it will require much work and documentation.

http://stinsonclub.org/PublicTech/Stinson_Seat_Mod/Stinson-108-3.pdf

 
Posted : 20/05/2017 10:45 pm
Brian
Posts: 566
Prominent Member
 

Gary Reddon put something together I believe, and it is a fairly interesting idea on getting more leg room. It was posted in the yahoo group. I'll see if I can find it and gets permission to put it in the public tech

Brian

 
Posted : 21/05/2017 3:03 am
Posts: 97
Estimable Member
 

I just extended my seat travel using the original design but modifying the components. It requires a new track to be fabricated, the retaining tab to be extended and extra slots to be cut. Then the components need to be welded back together. I used my brake, milling machine, drill press and mig welder. It could conceivably be done with some simpler tools. To get the last 1/4" of travel, I created a recess in the inside corner of the frame tube. To do this I made three small cuts with a hack saw and then hammered them in while supporting the tube on a curved dolly to spread the force of the blows on the outside of the tube. I then welded the cuts closed and ground them flush. In total It adds about 1+3/4" to the travel which should be enough for me (5' 11") but may not be for you mutants out there;) The recess in the tube could be optional but then the travel would be extended by 1+1/2.

I'm happy with this solution because it's so close to the original.

 
Posted : 25/03/2018 8:09 pm
Posts: 97
Estimable Member
 

Here's the optional recess for the full extension. In my opinion (and I'm not an expert) any weakness this might impart to the frame would be more than compensated for by the fact that the new track is welded into the corner, strengthening both.

 
Posted : 25/03/2018 8:42 pm
Brian
Posts: 566
Prominent Member
 

Please correct me if I am wrong, but it looks like the hole to remove the seat has been flipped from the front of the seat to the back, so to remove the seat you have to move it full forward instead of full back?

Thanks,
Brian

 
Posted : 25/03/2018 11:20 pm
Posts: 97
Estimable Member
 

That is correct. I couldn't think of a good reason why the original was the other way around and it allowed much more travel.

 
Posted : 26/03/2018 3:21 am
Posts: 300
Reputable Member
 

I noticed that too, orange4sky(name?). Does the mod allow you enough forward travel now so that the knob goes all the way to the back of the slot to get to the hole to tilt the seat back? I'm sure it must or you wouldn't have done it that way. Don't know why Stinson didn't design the seat this way in the beginning which would have prevented all of the seat dumps of pilots to the back. Happened to my Dad on takeoff in our Stinson 10A. Somehow he had presence of mind to let go of the yoke and managed to pull himself over to the other seat. I don't remember our 10A having the stop bolt in the track that our 108's have. Maybe a lesson learned from the 105/10A fleet? Lucky for short guys like myself(5'8") leg room is not an issue. I actually pull the seat forward to get to a comfortable position. But I'm a 1948 model, same as my Stinson. People were smaller back then.

Dennis Crenshaw. N6102M.

 
Posted : 26/03/2018 3:33 pm
Posts: 97
Estimable Member
 

The "track release hole" is in approximately the same place as the original stud/knob would have been when fully forward. I guess it will be a little more cumbersome to tilt the seat back but still manageable.

I may replace the retaining nut/bolt with a secure but quick release of some kind. My seat backs were assembled with clevis pins secured with cotter pins instead of nuts and bolts. Seems like a good idea to make inspection time easier but cotter pins are consumables so that might be a bit of a hassle.

 
Posted : 01/04/2018 8:52 pm
Posts: 300
Reputable Member
 

Yeah, there was a discussion some months back about replacing the bolt/nut in the track with a quick release pin. I did that, and it makes life much easier for tilting the seats back. You can get those at McMaster-Carr. https://www.mcmaster.com/#standard-quick-release-pins/=1c88bua

Do you have the later model dash 3 seats with the spring cushion supports? They are much superior to the earlier flat steel web supports. My seats feel like you're sitting on your living room sofa. Might be a problem with head room though if you're tall and have a thick foam cushion. But the earlier seats didn't provide any cushion at all once the seat pad got flattened with age.

Dennis Crenshaw. N6102M.

 
Posted : 01/04/2018 10:07 pm
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