fine thread needle on Norvel's and similar engines

[Ken Cook]

I provided these pics with an example of how I fitted the Cox 128tpi spraybar into the Norvel. Although my engine isn't a Norvel, it's a AME engine. Ame is now the designation of porting used on the Norvel engines. AME however was actually the name of the engine in the early 90's. I do own the AME Zeus and this case is almost identical to the Zeus it does have some differences. I'm 100% positive the spraybar assemblies are all the same diameter regardless of manufacturer with these Russian engines. I removed the brass spraybar from a red production backplate which has the 128 tpi needles which are the same as the KK needles used on the TD's. I then took a piece of 5/32" tubing and cut it to the width of the venturi. Keeping it a bit shy from one side to the other won't hurt and will actually help as the stock black seal that is used will have more room to fit onto.

In the pics, I show the spray bar inside the brass tubing soldered and epoxied into the aluminum venturi of the engine. The tubing is being used a bushing for the hole in the venturi. You need to drill a hole in the tubing so when the spraybar goes into it, the fuel has a way of getting out. I filed the opening larger than needed and aligned the hole in the spraybar with it. I highly recommend the use of JB weld here. The epoxy I use is West Systems T-88 which takes an extremely long time to set and will ultimately stay put. I'm not sure how the 5-30 min variants work as the T-88 has a 2 hour setup time. It's quite thick almost as thick as JB Weld. This mod will really test your soldering skills and how manly your fingertips are when you burn them off. I can hardly type now.

I cut the Cox needle down. The 5/32 tubing fits the Cox needle tightly and I solder a small piece over the needle. A 6-32 flat washer now fits over that and all is soldered. This keeps the needle close to the engine and out of harms way. I file a little notch in the washer for a reference. I want to try this out tomorrow. Most important is to not block the hole in the Cox spraybar with solder or epoxy this includes the threaded area as well where the needle screws into. Tip: when soldering a washer, use an xacto to scrape the plating off of the inside diameter. Flip the washer over and do both sides. I then sand the plating off on the underside which now takes all the solder. Solder doesn't adhere well to plating so I don't sand the top for appearance.

My initial attempt was to remove the aluminum venturi altogether. I do this by using a heat gun and a small adjustable grabbing the flats of the venturi rocking until it breaks out. This one wouldn't come out readily. I want to insert the same spraybar through the case where the holes are. You don't need the venturi. The spraybar would just be going through one side of the case to the other. It appears as though it may even friction fit as the knurling on the spraybar seemed to be large enough to press it into those holes. Ken

[fit90]

Ken,

I have read about that method but yours is the first time I have seen it. It looks great. You did a nice clean job.

I use an NVA from kittingittogether.com that has a slightly larger diameter than the Norvel Needle. I will try to post a pic later tonight. I have had very good luck doing this and using it on pressure fed engines but it is not as neat and clean as yours. I have to drill the venturi to fit the new needle. Then, to make sure the hole in the spray bar stays centered, I J B Weld it in place after I tighten the nut on the NVA. I tried it without glueing the NVA in place and the NVA moved on me.

Thanks for posting the pics. It looks great.

Bob

[Ken Cook]

Thanks Bob, I have the needle your talking about. I did press it into the venturi. It was quite difficult actually. I used my drill press like an arbor press to push it into the venturi. I certainly don't recommend that to anyone wanting to try it. I never used that needle with bladder pressure. This is an AME as well using a backplate pressure nipple and a hard tank. I have problems with the engine surging up and down. I really want to go out for all performance and remove the aluminum venturi and place the spraybar across the opening through the holes in the case. The Driskill spraybar is quite large probably the same as what I just bushed mine too which is 5/32". The Cox spraybar however is considerably narrower and therefore could use those holes in the case. I'm afraid of drilling the case knowing how fragile the casting is and having it break. I'm sure that grinding it would be ideal. Ken

[fit90]

The engine is a Norvel .061 AME Revlite.

[fit90]

same engine

[dckrsn]

Regarding the 128tpi assembly from KittingItTogether, I retro-fitted one into
a Cub .049b and it runs great. Starting was near impossible with the old one.
Bob

[fit90]

This venturi started out as a Big Mig venturi but has been rebored to match the AME's venturi, then it got the new NVA



On the engine in the previous pics I used a slice of fuel tubing in place of the venturi "O" ring. It works great.

[Ken Cook]

Bob, I'm a fan of JB-Weld regardless of it's appearance. I did use a high grade epoxy, I just don't know how it will hold up. In the event it turns, I'm out of luck. I do have the same set up as yours and I will give it a go. Trying to find certain specialty items for 1/2 A is becoming difficult. Props aside from APC and Cox are really hard to find. I wish someone would take over the Grish Tornado props once again as I see a real need for them. Ken

[gcb]

... Trying to find certain specialty items for 1/2 A is becoming difficult. Props aside from APC and Cox are really hard to find. I wish someone would take over the Grish Tornado props once again as I see a real need for them. Ken

A few comments and opinions:

That's a great looking intake!

The Grish folks were considering bringing back Tornado props but I understand that they would need to create new molds because the old ones are worn out. They decided to retire instead. At least this is what was posted some years ago.

I believe the crankcases on the NORVEL Big Mig and AME are the same. The cylinders make the difference. AME has three large transfer ports and Big Mig has five smaller ones.

The AME Zeus has no provisions for muffler since it was created for CL Combat. Mine has a plastic insert to allow suction feed. The Zeus had a fine needle so you could use a pressure setup. Here are some pics so you can see the size of the intake:





OK Cubs...The supplied needles in most are blunt causing one turn adjustment to go from slobbering rich to full lean. Another fix is to add more taper to the needle itself. It works.

George

[Ken Cook]

I've been told and I read somewhere on the internet that the AME engine line was school experiment. It was a class on engine building. I've heard the quality suffered on some of them while others dominated. I have no proof of that and I'm quite happy with mine. I have several versions of engines. My AME example above has the short case just like the AME Zeus. It does though have a milled recess in the casting at the exhaust for a muffler. Mine didn't come with a muffler. I do own a short case AME which came in a plastic bubble wrap pack that does have a muffler and spring starter.

All my AME engines have the AERO case with backwards Cyrillic E. All these engines are made in the same area of Russia. The Stels company used some of these cases but with there internals. I have several of these as well. Larry Driskill stated about how the AME short case made the best runners. I have a Stels that used the AERO case and its clearly evident that the AERO has been ground off. The case appears to be wire wheeled as it has a brush finish on it as well. The cylinder however looks identical to the AME and pre Revlite Norvel's but the cylinder is true ABC. I've had this engine turn 30 k with a Russian green prop. I believe this prop is 5 x 2 1/2.

On another note, I wasn't successful in using the needle that George shows in his picture of the Zeus. I didn't have a restrictor in my engine. I took a broken APC 5x3 prop, I drilled out the bolt hole and tapped it for 1/4 /32 threads. This is the thread size of a TD venturi. I then carefully filed and shaped with a sander the prop hub to fit into the AME case. I put a bit of epoxy around it inserted it into the case. By the time shaping was done and fit to the case with the through hole, it was almost in two pieces. I'm able to use a TD venturi and KK needle set up on the engine now. I drill the TD venturi to the max which is 5/32". Just another option on how to make and use a fine threaded needle. Ken

[RknRusty]

...I removed the brass spraybar from a red production backplate which has the 128 tpi needles which are the same as the KK needles used on the TD's. I then took a piece of 5/32" tubing and cut it to the width of the venturi. Keeping it a bit shy from one side to the other won't hurt and will actually help as the stock black seal that is used will have more room to fit onto.

In the pics, I show the spray bar inside the brass tubing soldered and epoxied into the aluminum venturi of the engine. The tubing is being used a bushing for the hole in the venturi. You need to drill a hole in the tubing so when the spraybar goes into it, the fuel has a way of getting out. I filed the opening larger than needed and aligned the hole in the spraybar with it. I highly recommend the use of JB weld here. The epoxy I use is West Systems T-88 which takes an extremely long time to set and will ultimately stay put. I'm not sure how the 5-30 min variants work as the T-88 has a 2 hour setup time. It's quite thick almost as thick as JB Weld. This mod will really test your soldering skills and how manly your fingertips are when you burn them off. I can hardly type now.

It looks like you used aluminum, 5/32" tube to enclose the Cox spraybar. When I solder it, should I lightly coat the inside of each end of the aluminum tube with flux, then heat each end individually until the solder just begins to flow, and stop? Then go to the other end and repeat?
I have rosin flux and 60/40 electronics solder.

Rusty

[Ken Cook]

Rusty, I used brass tubing to enclose the needle valve. What your seeing is the area I pre tinned. I tinned just the ends so that no solder would flow into the spraybar hole. I don't believe you can solder brass onto aluminum. I also didn't clean the center of the spray bar as I didn't want any solder to migrate there. I initially used T-88 epoxy to hold the entire assembly into the aluminum venturi. It did give up and the whole assembly started turning. I wire wheeled everything and used a little JB weld to hold it in. Ken

[RknRusty]

I'll solder the tip ends and put a little JB on the knurled rings on the spraybar to help hold it. And a dot of oil in the spray hole and flush it with acetone when it's partially set to make sure no JB is in there. This should work pretty well.
I was thinking of making a remote, but it looks easier to do this. I read about your suggestion of a Dubro collar in the other thread.
My needle shortening method is about like yours, just with a hex nut. Come to think of it the lighter weight of the T-nut might be a better idea. Thanks Ken.

Rusty

[RknRusty]

In between working on the Kitty Cat plane, I finally got to the HS and picked up some 5/32 brass tube that fits in the Norvel spraybar hole. Bored a hole in a section and inserted the Cox spraybar to see how it all lined up. It looked good, but for the life of me I could not get solder to seal it in there. So after a couple of clumsy tries, I cleaned off the solder and used my master gluing skills that I inherited from my Dad. There is now a good thick coat of JB Weld all over the inside of the tube holding the spraybar in place, with nary a drop in the spray hole. I'll let it polymerize for 24 hours and plug it into the venturi. I'll knurl the brass to hold it in place tightly and apply JB to that as well and if all works as planned I'll have another Norvel with a fine thread NVA that won't break loose and turn when I go to fly it. I would feel a lot more confident if I had been able to solder it, but it is what it is and that's what I've got... we'll see.

[Ken Cook]

JB weld is easily cleaned off using rubbing alcohol and a Q-tip for those interested in trying it. It cleans it quite well. Ken

[RknRusty]

JB weld is easily cleaned off using rubbing alcohol and a Q-tip for those interested in trying it. It cleans it quite well. Ken

You mean before it sets, right?

[Ken Cook]

Yes,prior to curing and I should've stated that. Ken

[pkrankow]

What about nitromethane softening the JB Weld?

Phil

[Mark Boesen]

Normal use it shouldn't affect it. Years ago (mid 90's) I JB'ed a Fuji .099 carb on after a crash, it's still solid. I've also read of drag racers reporting intake chambers on manifold and using JB. I've also used JB on custom model engine mufflers the heat there does seem to shorten life a little.

[RknRusty]

I've been flying a Big Mig that has a fine thread NV held in place by JB Weld on one of my Baby Streaks . It's secured with a nut too, but the JB keeps it from turning in its sleeve. I think Fit90-Bob made it, or either he bought it from Larry Driskill that way. When I remove the venturi to replace my latex seal after every 50 flights or so, I always pick at the JB to check it and it's still solid as a rock.

A side note to Norvel users: Latex bladder tube is the only thing I've ever been able to seal that wobbly venturi with. I tried all kinds of silicon tube rings and none work as well as the soft latex. Latex is said to beak down fast, so I replace it as a precaution, but so far I haven't seen a used one that looked bad when I removed it.

[Ken Cook]

Nitro has no affect on JB weld when cured. I use high nitro fuel above 35% on my Norvel's. My original install was done with T-88 Epoxy and I intentionally didn't scarify any part that was being glued. I just wanted to see how it worked. I wanted mine to be somewhat removeable and in my situation it loosened prior to me removing it. Ken

[RknRusty]

It came to me in the shower. I still have to look and see if what I imagined really works. That is to bore and tap a 2-56 set screw behind the spraybar. On the inlet side so as not to distort the threaded needle tube. This afternoon I'll take a look and see if it can really be done.

[RknRusty]

It fits nicely into the spraybar hole in the venturi.
I thought the setscrew in a 1/16" Dubro wheel collar was 2-56, but it's bigger and I don't have a tap that size. There's plenty of room for a cut down 2-56 hex bolt, so I'll use that. I didn't get to it this evening, but after I rebuild my mower deck tomorrow I should get some shop time to do that.

I'm not sure what size drill bit to use, I guess one bit smaller than the hole the screw fits through on the bit gauge. Maybe two smaller. I'll try on a test piece and decide. I looked at some drill and tap size charts but the terminology confused my little low IQ mind.

[pkrankow]

2-56 takes a #51 drill bit for 70% threads. A #50 drill is also considered acceptable for less thread depth in many applications.

Yes, I looked it up. Yes, it is pretty darn confusing. For most needs 50%-75% is acceptable thread forming, there is a balance between percentage and ease of cutting also percentage and east of the bolt fitting.

Phil

[RknRusty]

2-56 takes a #51 drill bit for 70% threads. A #50 drill is also considered acceptable for less thread depth in many applications.

Yes, I looked it up. Yes, it is pretty darn confusing. For most needs 50%-75% is acceptable thread forming, there is a balance between percentage and ease of cutting also percentage and east of the bolt fitting.

Phil

Thanks Phil.
A #51 is .067". I have a 1/16" bit which is .0625", maybe that would work.
My next bit is a 5/64"(.078) probably too big, as a #50 is.070".
Or I could go to the HW store and get the right bit. I believe this is cast metal I'm tapping into.

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