need help identifying a needle

[dwilfong]

what needle is this could use some help.

Building a proto type carb for a gas eng and this is the ticket.

But I don't know who makes it.

 

[SayMikey]

Looks like a OS

 

[Andy Brown]

OS Max .

Generally came on the .35 airplane engine. Us nitr boaters used the for decades. Not enough flow for todays engine much over a .21

 

[SayMikey]

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXCR44&P=7

 

[Andy Brown]

OS Max .

Generally came on the .35 airplane engine. Us nitr boaters used the for decades. Not enough flow for todays engine much over a .21

P.S. that is the needle we first used with the MAC 67 carb on the Zenoah. It was a one click needle. From good setting, next click was a bit rich or lean, next click was WAY off.

 

[dwilfong]

Thanks guys.

Don't need much flow for gas.

Flowed a gas carb and it was 120 and 160 on the high side needle at the normal setting used.

This needle has a real gradual adjustment in this range much better than any outer I flowed and I flowed them all.

 

[dwilfong]

I have a K needle and it was way more touchy.

Going to put this right on the carb.

 

[Andy Brown]

I have a K needle and it was way more touchy.

Going to put this right on the carb.

Now that I think about it, our OS Max needle was probably drilled out, so that is why is was sensitive. If it is smoother than the K needle it will surely be good, because we have a mile of range with the long taper K needle.

 

[dwilfong]

Did a bunch of testing tonight and pulled a modded WT257 with a .535 venturi apart.

Pulled all the plugs out of it and isolated the high speed circuit. had a .050 spray orifice in it and when I flowed the circuit it was between 120 and 160 with half a turn of the needle.

Going to use a .060 brass tubing for the spray bar and this needle on the carb right at the end of the spray bar.

Will put this on the flow box and check the vacuum and spray pattern at different points in the .600 x.785 carb boar.

This carb is equal to a .700 round carb but is the same shape and size of the port in the jug.

 

[El Zorro]

David, when we made venturis for our airplane nitro engines ( and later with boat engines ) we ran the spray bar ( or "stake" as we called it ) 1/3 of the way into the inside diameter of the venturi. The end was cut off at a 90 degree angle and NOT a 45 degree angle like many others that we all saw. A visit to John Ackerman's shop one afternoon confirmed this as John actually had a flow bench set up just for the purpose of checking for the best flow of fuel into the engine and best atomization of fuel mixing with air. I would think things wouldn't be much different with a gas engine set up. Something to think about..............

Dick Tyndall

 

[dwilfong]

Dick , I have done lots of test with nitro carbs and found the same with the barb placement on a round boar carb. about 1/3 in the boar works best for a spray pattern.

But there was always a dead spot behind the barb and a interruption in the pattern.

With a oval boar the end of the barb is best almost in the middle and there is a better spray pattern with no dead spot.

also the vacuum signal is better in a oval boar at the barb.

A oval boar is also the best way to fill the rectangular port in the jug as it dose not have to reshape the air fuel mix to enter the eng.

I have found that changing the shape of the air stream will separate the mix some and change the atomization of the fuel.

 

[RonShaw]

OS Max .

Generally came on the .35 airplane engine. Us nitr boaters used the for decades. Not enough flow for todays engine much over a .21

P.S. that is the needle we first used with the MAC 67 carb on the Zenoah. It was a one click needle. From good setting, next click was a bit rich or lean, next click was WAY off.

The taper on that needle is perfect for a 20. Anything larger and you will experience what Andy saw above.

 

[Glenn Quarles]

Dave, I keep those needles in stock for use on the 12 motors.

GQ

 

[dwilfong]

sounds good Glen I will get with you if this pans out to a production carb.

With all the gas boats out there I will need a few.

 

[Tom Foley]

Remember the Carl Brey carbs with a brass insert in the venturi area , full 360 , that had several holes around the inner perimeter to let fuel out in a full shower spray pattern . I have one , never ran it but always thought it would be the best method . LMK if you want to test it David .

 

[dwilfong]

I got one also and ran it on my Russian IR.21 It ran real nice.

Got some blank inserts with no holes made by BMC in Orlando for the holly dominator boosters. thy are .600

Will make a carb up to fit this in and give it a try.

Just a little small for what it is needed.

Don't want to go to crazy. This needs to translate to a CNC for production, easy to build and easy to use.

Les wants to make a few. His new head is selling like hot cakes. Needs a carb to go with it.

Dale gave me a few pointers on what makes his carb work so good. will incorporate this in to the final design.

 

[dwilfong]

Ready for the flow box this week for spray bar testing.

 

[ALLAN YUEN]

DSCN2115.JPG

DSCN2116.JPG

Ready for the flow box this week for spray bar testing.

Look Big Bore lot of thirsty fuel so need big tank 30 oz