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Author Topic: Rear needles  (Read 2491 times)

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Offline mo deller

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Rear needles
« on: January 16, 2007, 10:28:36 AM »
I've been thinking about buying an ASP 40 from JE as they are on offer for 40. However it is the rear needle option.

The only experience I have of rear needles is that of watching other people, and they always seem to be fiddling.

It could be that they are the sort of people who do that anyway but I get the feeling a rear needle is more prone to give trouble than one on the carb.

Are my instincts correct or are they no different?

Mo, :-\
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Offline Sizzling

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Re: Rear needles
« Reply #1 on: January 16, 2007, 10:39:28 AM »
Only expeiance of rear needle was an OS 46FX but that once set up I never had to touch. The thing that made it a bit harder to set up is you need to adjust it and wait a few seconds for the adjustment to take full effect. Your change may not be as instant as you are used too.

On the whole no problems and its a bit safer  :af

Offline Brian Cooper

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Re: Rear needles
« Reply #2 on: January 16, 2007, 10:55:20 AM »
Yup, spot on.  There is a slight dealy in new needle settings taking effect.  This does tend to confuse some people, which is probably why they seem to be forever twiddling with the needle.

However, once set up properly, there is little need to alter the settings.

B.C.

Offline Oggy

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Re: Rear needles
« Reply #3 on: January 16, 2007, 22:57:10 PM »
I too have OS 46AXs. Top engine, no problems.

Whether or not that applies to ASP is another matter.
"The preternatural - such a tiresome edict to we men of science".

Online Michael_Rolls

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Re: Rear needles
« Reply #4 on: January 17, 2007, 06:36:34 AM »
One point to remember - the rear needle was introduced (generally speaking) as a safety meausre - but it is only safer than a front needle if you adjust it (as one should, of course) from behind. If you adjust it from in front it can actually be MORE dangerous.
The reason - look at how you hold your hand to adjust the needle from in front. With a front needle on average sized engines, if you slip the prop is usually going to catch you on the fleshy ball of the thumb area - painful and messy but not too serious.
Now look at adjusting a rear needle from in front - the prop is likely to catch the inside of your wrist, potentially doing really serious damage to the arteries, veins and tendons in the area, all of which are very near the surface.

No - I'm not advocating adjusting the needle from in front - but some people still do.

Mike
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Offline mo deller

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Re: Rear needles
« Reply #5 on: January 17, 2007, 07:42:31 AM »
Looks like I've got no excuse now then  ;D better order one.

Don't worry Mike I've never fiddled with the needle from the front I much prefer doing it from behind  ;D

I learnt a lot of years ago when I was about 10 with a DC Merlin.

Thanks for the replies, Mo,  :)
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Offline tomkfly

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Re: Rear needles
« Reply #6 on: January 17, 2007, 08:24:11 AM »
It's very easy to convert a rear needle to front needle. All you have to do is remove the plug out the left hand side of the carb.,unscrew the needle valve assebly from the rear bracket and screw it into the hole, in the carb., that the plug came from.



   Tom
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Offline Sizzling

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Re: Rear needles
« Reply #7 on: January 17, 2007, 09:07:18 AM »
It's very easy to convert a rear needle to front needle. All you have to do is remove the plug out the left hand side of the carb.,unscrew the needle valve assebly from the rear bracket and screw it into the hole, in the carb., that the plug came from.

You couldn't do this the OS so only applys to some  :)

Offline tomkfly

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Re: Rear needles
« Reply #8 on: January 17, 2007, 09:13:26 AM »
Quote
You couldn't do this the OS so only applys to some  Smiley

The original post was about an ASP40 and I should have made it clear I was talking ASP.


     Tom
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Offline Sizzling

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Re: Rear needles
« Reply #9 on: January 17, 2007, 09:17:07 AM »
Couldn't on my 46FX. The carb is a completely new case and the main jet side is blocked off as part of the moulding. Different line of engine, different way of doing things  :)

Offline tomkfly

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Re: Rear needles
« Reply #10 on: January 17, 2007, 09:55:19 AM »
Couldn't on my 46FX. The carb is a completely new case and the main jet side is blocked off as part of the moulding. Different line of engine, different way of doing things  :)
I don't know a lot about modern OS engines. It sounds like the 46FX is made specifically as a rear needle motor. However, ASP/SC/Magnum .25 to .91 twostrokes are sold in both configurations and use a common carb. body. Converting a rear needle job to front needle, on them, is a simple job.


    Tom
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Offline Sizzling

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Re: Rear needles
« Reply #11 on: January 17, 2007, 10:08:10 AM »
Worth knowing that Tom, thanks  :af

Offline tomkfly

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Re: Rear needles
« Reply #12 on: January 17, 2007, 10:35:49 AM »
I have just checked the theory by converting an ASP36 from rear to front and back again. The plug and needle assmbly are very tight and have a very thin, paper looking, gasket under them. You need a good (not worn)  5/16A/F spanner and support the rear bracket ( you don't want to break it in case you want to convert back). Job only takes seconds to complete.
If you buy the engine as a front needle motor you may not get the bracket to convert it to rear, but they don't cost a lot from JE. :af



   Tom
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Offline mo deller

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Re: Rear needles
« Reply #13 on: January 17, 2007, 14:28:17 PM »
It's very easy to convert a rear needle to front needle. All you have to do is remove the plug out the left hand side of the carb.,unscrew the needle valve assebly from the rear bracket and screw it into the hole, in the carb., that the plug came from.



   Tom

Thanks for that Tom,could be useful. Anyway I've placed my order for two!

Well I didn't get any model stuff for christmas so why not ?
My name is Mo
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Goin' against the flow Don't ya know.

Offline tomkfly

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Re: Rear needles
« Reply #14 on: January 17, 2007, 14:36:08 PM »
Why not, Excellent engines and a bargain at 40 :af


    Tom
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Offline Spiffy

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Re: Rear needles
« Reply #15 on: January 17, 2007, 17:54:01 PM »
I too have OS 46AXs. Top engine, no problems.

Whether or not that applies to ASP is another matter.

I have two ASPs - no problems at all - one is a 1.08 which is a bit larger than your purchase but both ASPs perform flawlessly, the larger one is  awesome, starts easily and very reliable.
Spiffy
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Offline Gaspin

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Re: Rear needles
« Reply #16 on: January 22, 2007, 09:14:10 AM »
I have an ASP 53 runs great on rear or front mounted needle valve, actually I run it on the front as that is where the hole in the cowl was, but starts easy and runs great. Just a thought, on smaller sized engines with rear mounted needle valves I always seemed to be breaking the bracket off, any time the engine moved slightly in an interesting arrival!! the traditional fitting seemed to be a more robust location.

Gaspin :co

Offline chris mann

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Re: Rear needles
« Reply #17 on: January 22, 2007, 11:56:55 AM »
I have an OS 46 ax .Totally agree about the bracket breaking on unexpected arrival. Best to get a few in as spares the OS ones are 3 from just engines if i remember right. Only prob i have is if there are air bubbles in the fuel line which tend to get trapped half way along the connector pipe between the needle and carb. I just lift the plane up and let them clear before tuning the engine as they can mess the mixture setting up. So fit clear piping so you can see whats going on!

Cheers
Chris   

Offline GFR

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Re: Rear needles
« Reply #18 on: January 24, 2007, 08:58:46 AM »
A lot more people would probably fiddle if it wasn't so dangerous.

Offline mo deller

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Re: Rear needles
« Reply #19 on: January 24, 2007, 09:24:19 AM »
A lot more people would probably fiddle if it wasn't so dangerous.

 ??? But I thought rear needles were a safety feature, shouldn't be dangerous if it's done proper  :)

Anyway I am now the owner of two ASP 40's. The carb and rear needle stuff come separate which would seem to suggest that they are a bit vulnerable as Gaspin and Chris have said.
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Offline tomkfly

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Re: Rear needles
« Reply #20 on: January 24, 2007, 09:38:26 AM »
I believe the reason they come separate is to allow you to decide for yourself wether to have a rear or front needle. The rear bracket on an ASP is a bit stronger than the one fitted to OS but they will still break if you manage to bury the engine, up to the backplate, during an unplanned return to terra firma.



    Tom
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Offline Scram

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Re: Rear needles
« Reply #21 on: January 27, 2007, 19:35:05 PM »
I never liked the needle valve so close to the spinning prop in the normal carb position on my OS40 FP powered Flair Cub.  Also in that position the needle fouled on the cowl and when I saw the rear needle option in the engine handbook, and could not get one, I did it myself.

Got a complete new needle valve assy and mounted this on a bracket off the back plate.  Removed needle from carb, cut off thread for the needle and soldered a bit of tin plate on to block off the needle hole.  Connected carb fuel input to the spray part of the remote needle and Bob's yer Uncle, worked perfectly  :D

Now the Cub has gone the everlasting cloud in the sky - er, hole in the ground, I'm finishing off me Patriot and fitting an OS 50 SX-H I have spare.

This again gives me a problem of needle access.  Close to the prop and clashing with the curve of the cowl so I have mounted the OS 40 needle assy off the Cub onto a bracket on the front bulkhead so that the needle now comes out of the top of the cowl well away from the prop.  Easy to adjust, on top of the model.

It remains to be seen whether this needle will pass sufficient fuel for the OS50.   ???

Oh, I just unscrew the original needle on the engine till it is only just in, sealing on the o-ring and held by the ratchet spring.

Hopefully will work a treat again   ^-^

GJ
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Offline Spiffy

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Re: Rear needles
« Reply #22 on: January 27, 2007, 20:38:04 PM »

 Doubt that you will find much difference on the new engine using the old needle valve. Probably about half a turn open out more or maybe even less.  Should be plenty of adjustment in hand a main needles.
Spiffy
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Offline GFR

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Re: Rear needles
« Reply #23 on: January 27, 2007, 22:55:57 PM »
?? But I thought rear needles were a safety feature, shouldn't be dangerous if it's done proper  :)


No I meant that if you put the needle in a safer position it might encourage people to fiddle. Why do you think these old boys keep engines of all types and ages running often at considerable time and expense? It is because they love engines. We get the fun of flying (mostly) and of fiddling (even to the detriment of our flying sometimes when we forget "If it ain't busted don't fix it". No - fidling is like gazing into a wood or coal fire or maybe watching the wave at the seaside or touching paint to see if the "Wet Paint" notice is current. Aint you got no romance ?

Offline mo deller

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Re: Rear needles
« Reply #24 on: January 28, 2007, 08:31:10 AM »
No I meant that if you put the needle in a safer position it might encourage people to fiddle. Why do you think these old boys keep engines of all types and ages running often at considerable time and expense? It is because they love engines. We get the fun of flying (mostly) and of fiddling (even to the detriment of our flying sometimes when we forget "If it ain't busted don't fix it". No - fidling is like gazing into a wood or coal fire or maybe watching the wave at the seaside or touching paint to see if the "Wet Paint" notice is current. Aint you got no romance ?

Sure I do but fiddling to try and get an engine to keep running so you can fly is one thing and just playing for the sake of it is another.

Mo, :)
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Offline GFR

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Re: Rear needles
« Reply #25 on: January 28, 2007, 17:00:27 PM »
Sure I do but fiddling to try and get an engine to keep running so you can fly is one thing and just playing for the sake of it is another.

Mo, :)
Got to admit I do try to use my engines way after there useful life. So there's a whole stack of fiddling time. Two years ago I dumped a Fox 35 C/L engine I had converted to carburator way back in the days of turnups and black and white tele! Still fondle my Ollie though.... Too many interests to keep upto date.

 

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