Stinson running adjustment

[Weeds round the prop]

I'm not sure which forum this belongs in but it seems historical:
Does anyone have an idea of what is being done in this picture?
I cannot find the original photo on the net.
The aircraft is a Stinson Junior, and there seems to be some
form of grab rail fitted over the cowl, and a 'platform' either side of the nose
that the brave 'mechanic' is lying on.

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/450x321/_cid_16c84727d4a732789161__f65a83935a1d8c61552f6fe479a5e1c11 78a9405.jpg

[megan]

Perhaps this one on a test flight?

SM-4 Junior 1929 = 2pChwM rg; 300hp Wright R-975. POP: 1 special retractable-gear endurance plane Sally Sovereign developed from SM-1 [X9696]. Damaged in a wheels-up landing after a failed endurance flight (p: Eddie Stinson, Randolph Page). Rebuilt with fixed gear as K of New Haven for an aborted attempt at a US-Argentina non-stop flight on 7/15/30, when the crew became lost in a fog over Georgia and ran out of gas. They bailed out and SM-4 crashed to destruction.

Stinson (http://www.aerofiles.com/_stin.html)

[DaveReidUK]

Not a Junior - it's the SM-1 Detroiter "City of Chicago" used by the Hunter brothers for their 1930 endurance record flight:

https://www.criticalpast.com/video/65675059964_endurance-flight_Sky-Harbor-airport_mid-air-refueling_Hunter-brothers

[dook]

There is more than one photograph of that event.


https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/650x525/airplane_20mechanic_20on_20wing_e3c7d60d5e0ee30dd9f5d0c35033 cba1ab04aae0.png

[dook]

Here's another.


https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/640x507/5ecd0d_ee30880c2f234719b04b6ea685aab9e4_mv2_150359a8ceaf1e0c adc88d8e43bb99f226f6647c.jpg

[treadigraph]

Had a flight in the right hand seat of an SM-8 Junior about 20 years ago, glad I wasn't asked to do whatever he was doing...

[dook]

What he was doing is captioned in my post #4 above.

[treadigraph]

Thanks, missed your first pic on me phone...! And Dave's post 3.

[spekesoftly]

What he was doing is captioned in my post #4 above.

I'm struggling to understand how the the intrepid gentleman was able to change the spark plugs with the engine running?

[dook]

I wondered about that too, but it seems they did.

[dook]

Yet another:


https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/338x500/twenty_three_days_air_0_84b94722b29126b030bd1078ec1ae042aa05 6c6c.jpg

[Weeds round the prop]

Thanks everyone.
It appears that this was such a common, and indeed necessary, procedure that the 'access frames' and grab rail were fitted for the purpose of allowing a passenger (hopefully!) to carry out this work. I still find it hard to believe that a spark plug can be changed on a running engine, having witnessed the result of one unscrewing to the end of its thread and zipping off over a hedge, never to be found again- I was following a BSA 441 Victor at some speed many years ago.
Regards, Weeds

[dook]

It wasn't a passenger.

[Weeds round the prop]

Oh, and thanks Dave Reid: I can see now that the large hatch/hole behind the cockpit was where the in-flight refuelling hose was dropped into (and probably food and drink too). I presume that the PNF had to catch hold of it and connect the end to a fitting on a fuel line to the tanks. Brave aviators!

[Planemike]

Where was the Health & Safety manager when all this was going on....???!!!

[dook]

Flying the aeroplane !

[Jhieminga]

I still find it hard to believe that a spark plug can be changed on a running engine, having witnessed the result of one unscrewing to the end of its thread and zipping off over a hedge, never to be found again-
A largish radial will continue running even if one cylinder isn't cooperating. So if you pull off the lead(s) for one pot at a time, you should be able to change the plug(s) that way. The difficult part is probably getting the new plug in without dropping it ;)
Not saying I'd like to take on the job though....

[megan]

Changing plugs? Poor maintenance, what about the timing, tappets, oil change. ;)

You're an ace Dave with that link. :ok:

Hand starting.

https://cimg2.ibsrv.net/gimg/pprune.org-vbulletin/400x356/a6ccb29e0969482b7ed482182b887132_dab2081dee597adbe142fabd4f5 cc76fcae6eee3.jpg

[washoutt]

But how do you push a spark plug into its fitting in the cilinder head against the pressure of the cilinder coming up? That's a pressure in the order of 5 or 6 atmosphere, leading to force of around 40 to 70 kgf (500 N methink), depending on the diameter of the spark plug.

[DaveReidUK]

But how do you push a spark plug into its fitting in the cilinder head against the pressure of the cilinder coming up? That's a pressure in the order of 5 or 6 atmosphere, leading to force of around 40 to 70 kgf (500 N methink), depending on the diameter of the spark plug.

Time it so that you screw it in on the down-stroke. :O

Joking aside, I was wondering how they would do that too, and also how they would reach all 9 cylinder heads.

Not to mention how much/little clearance there was between the forward plugs and the prop ...

[dixi188]

I wonder if there was a compression lifter on the valves, (like on some old big single motorbikes), so that there was no compression on the cylinder having the plug changed?

[DaveReidUK]

I wonder if there was a compression lifter on the valves, (like on some old big single motorbikes), so that there was no compression on the cylinder having the plug changed?

You could well be right.

Wright Aeronautical Corporation - Compression-Relief Device for Internal-Combustion Engines (https://patentimages.storage.googleapis.com/84/21/75/126ef1d5569108/US1439798.pdf)

[dook]

Now there's a nice piece of research.

[meleagertoo]

I'd still be surprised if even a compression - relief valve would allow fitting a plug.

They had all the time thay wanted to do this so my guess would be a climb to 10,000 ft with mechanic outside and ready, shut down and stop the prop, change plug(s) in the glide and restart. Repeat as necessary.

This link to the efforts of the previous year 1929 when the endurance record was broken 9 times!
Interesting to note the comments about exiting the aircraft to grease rocker arms and "adjust" magneto and spark plugs.
https://generalaviationnews.com/2015/05/10/1929s-record-setting-endurance-flights/

Video
https://dissolve.com/video/World-endurance-flying-record-broken-Hunter-Brothers-royalty-free-stock-video-footage/001-D378-15-096

A family affair
https://daysgoneby.me/have-you-ever-heard-of-the-famous-aviators-the-hunter-brothers-from-illinois/