How many turns?

Mark,

Have a look at the instructions of the Cox Stuka. This plane has a 290. The instructions say to open the needle 3 1/2 turns for starting:

https://www.coxengineforum.com/t5163-cox-ju87d-stuka?highlight=cox+stuka

Have fun!!

Lieven

Yet another example of why I shouldn't post information at 4:30 am.

RknRusty wrote:Yet another example of why I shouldn't post information at 4:30 am.

  That's OK Rusty... 3-1/2 turns doesn't seem like enough for a 128 TPI needle..   (how could it be?) Maybe because of how you mentioned that the needle has a blunt point..as compared to the "Bee-style" sharp-pointed needles?

I misplaced one of my two fine-thread needles..   

Here's a pic of the two I had... Notice the difference in the needle-tip profiles.. Would the seats in the spray-bars be different too?




and here's a pic showing the difference between an 80 TPI needle on the left (from a horseshoe) and a 128 TPI needle on the right (from a 290/postage-stamp) This is the needle that I misplaced.

I don't know the answer to that but..if it don't fit I was not made for it !! I would say they are different? just a guess though. Mark my racer engine was set on 3.5 that was 20K I would start with 4-4.5 that should get you running   Getback

getback wrote:I don't know the answer to that but..if it don't fit I was not made for it !! I would say they are different? just a guess though. Mark my racer engine was set on 3.5 that was 20K I would start with 4-4.5 that should get you running   Getback

I can't remember Eric.. were you running a bladder.. or suction? (at 3-1/2 turns out, I'm guessing it was suction) Was your NVA swapped from a 290 backplate.. or was it a Texas-Timers unit?

Mark, are you trying to run a 290 "engine".. or did you swap it's NVA out to a "Horseshoe"? Just curious... I can hook you up with mounts for the 290. They're thin enough (.040" alum.) to fit under the OEM case-screws with plenty of extra thread-length to tighten safely.

roddie wrote:

Mark, are you trying to run a 290 "engine".. or did you swap it's NVA out to a "Horseshoe"? Just curious... I can hook you up with mounts for the 290. They're thin enough (.040" alum.) to fit under the OEM case-screws with plenty of extra thread-length to tighten safely.

It's a 290 backplate. I was going to wait until you got things shook out on your 290 mounts, and then get a set from you to build a "290 Special" with.

The "Special" Mark

I am sorry my backplate ended up being a .....128 thread/ black plate I got from another engine / super bee crank / case / super dupper p/c / suction system     Getback   

batjac wrote:

roddie wrote:

Mark, are you trying to run a 290 "engine".. or did you swap it's NVA out to a "Horseshoe"? Just curious... I can hook you up with mounts for the 290. They're thin enough (.040" alum.) to fit under the OEM case-screws with plenty of extra thread-length to tighten safely.

It's a 290 backplate.  I was going to wait until you got things shook out on your 290 mounts, and then get a set from you to build a "290 Special" with.

The "Special" Mark

Yea.. that's a cool looking little airplane. I'll make you the specified "L"-mounts for it then; that screw to the top/bottom of the hardwood nose-block. I can bend the plates to 90 degrees on the backplate side.. but you'll have to "open them up" to match your bevel-angle on the nose-block... which looks to be around 110 degrees or so, on the plans.

A couple of "290 Special" building considerations to think about.. I mentioned in the "postage stamp mounting" thread; that the wheels used on that model back then (Veco) would have been quite heavy.. If you use lighter-weight wheels combined with my engine-mounts (which are aluminum and NOT steel), you may want to go with an "all sheet-balsa" tail-plane.. rather than the specified ply/basswood pieces.. so it won't end up tail-heavy.   

BTW... If you can measure the Pee Wee's case mount pattern.. I could make similar "L"-mounts for those "Sky-Copter" backplates you have. If you trimmed one "square".. as per the "290 Special's" design, you'd have a super-lightweight .020 with a much reduced frontal-area for less wind resistance. Were there any other plastic (product) backplates made for the Cox .020 reedie.. other than the "Sky-Copter's"??? Let me know if that's something that would interest you.