Cox Engines Forum
You are not logged in! Please login or register.

Logged in members see NO ADVERTISEMENTS!


Vintage pneumatic Fuel cut off engine timer Cox_ba12





Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Cox Engine of The Month
January-2023
1/2A Nut's

"Tee Dee .020 RC"



PAST WINNERS
CEF Traveling Engine

Win This Engine!
Gallery


Vintage pneumatic Fuel cut off engine timer Empty
Live on Patrol


Vintage pneumatic Fuel cut off engine timer

Go down

Vintage pneumatic Fuel cut off engine timer Empty Vintage pneumatic Fuel cut off engine timer

Post  rfara Tue Dec 06, 2022 1:38 pm

Greetings-  Does anyone know how to set up a vintage pneumatic type fuel cut off engine timer?  The one that I would like to use with a TD or Pee Wee 020 is nice and small/lightweight and it is branded "Spitfire"  I do not have any instructions for how it works and how to configure the fuel lines.  Photo is included.  Any advice is appreciated.

Vintage pneumatic Fuel cut off engine timer Pxl_2010


Last edited by rfara on Tue Dec 06, 2022 3:06 pm; edited 1 time in total (Reason for editing : word revision)
rfara
rfara
Moderate Poster
Moderate Poster

Posts : 13
Join date : 2022-03-09

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  ffkiwi Wed Dec 14, 2022 3:30 pm

Well I wouldn't recommend using it at all-these timers (the airdraulic type-not just your particular branded one) were notoriously inaccurate and troublesome in their day-late 40s-to late 50's-and disappeared off the market very quickly when clockwork timers became readily available. The problem is they used rubber and leather parts internally-and neither material ages well.

There is no way you could use your example with a PeeWee...unless you are prepared to cut a hole in the tank and use an external fuel line. It could be used with a TD 020-but again you would have to a) find a place to mount it-so that means at best behind the engine in the fuselage-or hanging out in the breeze-but again behind the engine-and then the fuel line will be convoluted-you have to plumb the timer between the tank feed and the needle valve assembly-that's what the two fuel nipples on top of the timer are for-its simply a shut-off valve. Note that there are other types of timer operating the same way-some cut the ignition circuit on a spark engine, others crush the fuel line-but they all suffer from the same genera issues of unreliability and repeatability.

If your usage is such that you don't need an accurate engine run-then fine....but you could then achieve the same result with an eyedropper tank or a graduated coil of fuel tube-at a lot less hassle.

The reason such timers became notorious is due to their intrinsic design mechanism-they all work essentially on a 'syringe' system-there is a piston inside that is propelled down the body by a spring-which is compressed when the operator pulls out the operating lever....the piston uses leather or rubber gaskets to achieve a seal within the body-and the rate at which it moves down is governed both by the spring tension and an adjustable bleed valve at the base-normally adjusted by a needle valve-adjustment of which speed up or slows down the rate at which air can escape....and in turn determines the time taken for the piston to reach the limit of its travel-at which point the timer carries out its function. Sometimes the adjustment is built into the knob on the operating lever-but the principle is the same. Friction, dust lubrication all have a major effect on the reliability and repeatability...

Some brands-the UK 'Elmic' for example, had versions that triggered a sprung loaded arm that could pivot though about 45 or 90 degrees when triggered-and operate a separate shutoff mechanism on the engine when the timer operated. and some incorporated two functions-the second being via the aforementioned arm-so for example could operate an autorudder function as well as engine shutoff. Ingenious...but still a flawed concept.

ChrisM
'ffkiwi'

ffkiwi
ffkiwi
Gold Member
Gold Member

Posts : 271
Join date : 2018-07-10
Location : Wellington, NZ

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Vintage pneumatic Fuel cut off engine timer

Post  rfara Wed Dec 21, 2022 9:56 am

Thanks for the detailed information. I'll pursue eyedropper type tank for this application. The mechanical fuel cut off timers that I have are too heavy.

Best Regards
rfara
rfara
Moderate Poster
Moderate Poster

Posts : 13
Join date : 2022-03-09

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  ffkiwi Wed Dec 21, 2022 3:14 pm

rfara wrote:Thanks for the detailed information.  I'll pursue eyedropper type tank for this application. The mechanical fuel cut off timers that I have are too heavy.

Best Regards

Mike Woodhouse in the UK offers a very small light clockwork cutoff timer-you can find out about them here: https://www.freeflightsupplies.co.uk/index.php/products/timers-d-t-fuse-etc     [scroll down till you reach the 'Mini Timers' section...]

Hank Nystrom of Texas Timers also offered (but no longer does) a very small clockwork timer based on a similar mechanism (but using a scroll release, not a rotating arm as in the Woodhouse unit) known as the Texas 'Micro'.....these occasionally pop up on Ebay, so worth keeping an eye out for. either unit weights about 5 grams...so way less than the  bigger metal ones-KSB, Tatone etc

Either type is ideal for 020 models if an accurately timed engine run is required. The Woodhouse one will give you up to about 25 seconds run, the Texas timers one up to about 28 seconds-when set to their maximum run length.

ChrisM
'ffkiwi'
ffkiwi
ffkiwi
Gold Member
Gold Member

Posts : 271
Join date : 2018-07-10
Location : Wellington, NZ

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  rfara Thu Dec 22, 2022 9:25 am

Thanks again ChrisM.
Do you know if there is any way to set up one of Mike Woodhouse's lightweight clockwork pinch off timers with a Cox Pee Wee 020 with integral tank/mount? I'm not sure how I would configure the fuel line in this scenario. I know how it is done with the Tee Dee version.

Bob
rfara
rfara
Moderate Poster
Moderate Poster

Posts : 13
Join date : 2022-03-09

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  GallopingGhostler Thu Dec 22, 2022 10:46 am

I drilled a hole same diameter as fuel tubing in the bottom of my Pee Wee tank and connected the tubing to the fuel barb on the tank back venturi pickup:

Vintage pneumatic Fuel cut off engine timer Ace_rc11

Then I passed the line through the firewall of my Littlest Stick to a larger Perfect wedge tank mounted vertically as one would for free flight use. Photo shows the vent side of the tank. The fuselage opposite side has the fuel fill nipple.

Of course doing such then ruins the Pee Wee tank for future use.

May be about a year ago, someone had made a limited run of 3D printed Pee Wee backs modeled after the Sure Start horseshoe backs, was being sold on either Cox International Canada or Ex Model Engines in US or both, but are not shown there now.
GallopingGhostler
GallopingGhostler
Top Poster
Top Poster

Posts : 3842
Join date : 2013-07-13
Age : 68
Location : Clovis, NM, USA

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  ffkiwi Sun Dec 25, 2022 12:43 am

George is right-the only way to use a Peewee with a timer is to drill the tank bell for an external fuel line. Ideally this would be done using a spare tank bell...which you could buy ready drilled from Kustom kraftsmanship when they were in business. These days I would try and tap the hole so that it could be filled with a short sealing screw (you'd probably need a plastic or rubber washer as well under the screw head) if you wanted to revert to normal usage of the PeeWee. I'd be inclined-on reflection-to use a 3mm or 4mm nylon screw (or the UNC equivalent in nylon) -and perhaps a nut on the inside to keep it tight. Its possible that if you wanted to 'revert' the drilled tank back to near standard, a suitable diameter pop rivet would work as well as a screw-though the rivet would not be easily reversible, obviously.

ChrisM
'ffkiwi'
ffkiwi
ffkiwi
Gold Member
Gold Member

Posts : 271
Join date : 2018-07-10
Location : Wellington, NZ

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  rfara Thu Dec 29, 2022 12:34 pm

Thanks again.
I have a couple of pee wee 020 tanks from non-working engines that I can drill/modify for this.

I'll send photos of the plane with final engine timer solution once finished.

Bob
(rfara)
rfara
rfara
Moderate Poster
Moderate Poster

Posts : 13
Join date : 2022-03-09

Back to top Go down

Vintage pneumatic Fuel cut off engine timer Empty Re: Vintage pneumatic Fuel cut off engine timer

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top

- Similar topics

 
Permissions in this forum:
You cannot reply to topics in this forum