Model Engine Maker
Engines => From Plans => Topic started by: Trevorc on February 01, 2021, 07:46:20 PM
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Hello
Does anybody have advice on type and source of suitable needles for use in needle valves on carb.
My current project, an Anzani Y , specifies a 1/16 inch hole in jet and a 1/32 inch diameter tapered needle.
Have used small diameter sewing needle BUT these have a curved point not a nice uniform taper as the drawings suggest. Using sewing needle means that the control of fuel flow is either “ all or nothing” there is not incremental increase in flow are at exit from jet.
Have others encountered similar problems? What was solution?
Thanks in advance for any help.
Trevorc
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I've made a number of successful carb needles by placing the drill rod or music wire needle in the lathe chuck, The Dremel tool with an alum oxide wheel is placed in a holder on the toolpost, and the compound rest of the lathe set to the needed taper angle. My lathe is an old worn out 9" South Bend. I use the compound rest's leadscrew to move the grinding wheel across the needle end (using very fine feeds) until the needle is finished to a fine point and nice smooth finish. Very slow to do, and limited to about 1.5" of taper, but gives a good result. The lathe ways are covered with a cloth during these ops to keep the grinding dust out.
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I use sewing needles. You can buy a pack of various sizes from any fabric shop. I never had luck trying to make my own needle.---Brian
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Hi Trevor, I've described the method I use a few times on here - such as https://www.modelenginemaker.com/index.php/topic,1334.120.html (https://www.modelenginemaker.com/index.php/topic,1334.120.html) - scroll to post #125
I've made quite a few needles in this manner all of which have worked well with the basic needle valve assembly used in IC diesel engines. Simple to do and effective.
Might be worth a look ?
Regards - Tug
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Interesting link, thank you Ramon