MJD

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Have you seen these 3x3 props?

http://www.amainhobbies.com/rc-drone...503302/p467799

I think we should keep going until someone hits 100 with an .010.

MJD

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3x4 3-blade props?



3x4.5 two-blade? I can make these - get some MA 5x4.5 and chop off an inch from each blade.

Pond Skipper

Awesome got to get some to try with the TD .020

The hub is too big in dia. for the MA and material weight is an issue.

MJD

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Oh yeah, I was just kidding on the MA - I meant these were kind of chunky looking. There is a 4x4.5 prop too - it looks exactly like this without 1/2" chopped off the tips.

The 3x4 only have to spin a bit over 25k to have three digit potential. Hmmm.



Missing: bigger balloon, 1 x HS-35, linkages and hinges, finish, who knows what else.

MJD

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New 6cc balloon tank. It, plus the previous 3cc tank still don't register 1g. It's a cheap scale but it checks out to the gram on calibration weights to 100g. The larger tank uses a nylon 10/32 x 1/8" barb fitting, with a silicone washer threaded over the 10/32 threads and locked in with a tapped fiber washer (this is all McMaster Carr stuff.. Spaenuer fittings and the like). The balloon was stretched over the nice soft washer (1/2" od) and some of the excess neck pulled over and trimmed off. Funny how long these latex balloons hold up to hot fuel, I soaked one in 50% for a few days and it looked fine to me after.


<-- Texas Timers silicone tubing and a drilled black backplate. I angled the needle forward to help the line stay short and unkinked.

aspeed

Good scale, I just used mine 10 minutes ago. Sale item from Crappy Tire for $10. I never touch my triple beam balances any more. Is the tubing in the balloon tank going all the way to the back of the balloon, or about half way?

MJD

My Feedback: (1)

Neither so far, just the inlet at the fitting itself. Will see how the fuel head varies and go from there I guess. I fill it same as a Jett or Tettra tank - pull back to evacuate all the air, then fill air-free. It will need some support in there, and the (smaller) Lipo will go below or beside for balance.

That scale is decent except for fine weighments. I got mine at Crappy Tire for about that too, some big sale last year. I'm still in mourning for my old scale , inherited at my last job about 9 years ago - a Sartorius 600g x .001 / 6kg x 0.01g lab scale. I jealously guarded it for a long time and had great fun obsessing over excessively fine measurements. Then one day someone using my scale who did not understand about shock loads from heavy rigid objects... well, that was the end of that extravagant little treasure. Used replacements are hundreds of bucks.. not happening! Now he lends me his Ohaus triple beam when I need a more accurate scale.. not quite the same.

MJD

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I've been fussing with balloon tanks and tubing - that Texas Timers tubing is nice stuff but doesn't grab worth beans on the TD fuel inlet nipple. It is like a timer, the tubing works itself off with slipstream and vibration after 10-30 seconds running. Every time. So back to the old school tubing, I formed it to shape with a BIC lighter and a piece of solder shoved up the center. Now it pops on and off the fuel inlet nicely.

I hate changing plugs on .010's but sometimes you gotta. Bench running with the balloon tank today - just could not needle it to a steady setting, rpm was down, and duh look at that the rpm drops when I pull plug heat. I had already made fresh fuel to rule that out. It feels like sacrilege cracking a glow plug package. But fired it up.. oh there we go, steady rich two cycle and it ran off about 4cc of fuel without a fuss before I shut it down. Today I tried out the O'Donnell 25% / 8% syn oil car stuff with castor added to 23% total oil. The .010 and even a refurbished Dragonfly seemed to like the taste.

Pond Skipper

2 Feet of Small Super Blue Silicone Tubing from Du-Bro. works well on the TD .010.
Yes a slight angle with the nipple helps as you have found. Here is another thing some NV work better than others I have found up to 2k difference in performance with hard tanks. Slight variance in design some take a few turn some take many turns out to find the sweet spot. Prior to testing a used ebay buy I always pull the NV and force fuel through the small hole to the venturi holding the hole for the NV close with my thumb brapping the pressure thru thumb control.
All the same variances are found. I have one NV assembly where the small hole has been opened up slightly it takes less than a 1/4th turn from closed to set the needle the engine screams very well. My worst one takes around 6 turns out.

MJD

My Feedback: (1)

I think that's the small tubing I have, and the stiffness was causing it to pop off the nipple as soon as I bent the tubing. Wish there was a tiny elbow on the NV/spraybar assembly.

Pond Skipper

The choice to have the fuel line come out behind the cylinder through the engines back plate the curve is difficult to hold. I have used piano wire inside small metal tube to help from a short aggressive bend with 1 mm ID.This should help with whatever fuel line on hand now.

Another method worth considering the IV drip line tubing that is sold as 1/2A line hardens over time very quickly after fuel has gone through
it perhaps you have some already curved as as coupler to take the stress off the nipple connection. When new it grips very well if you have the
right size it just can be removed for fueling. Maybe a solder up a brass micro T drill out after soldering allowing you to take advantage of the
initial superior connect IV line can provide. Pressure line is tough this size a fast, leak proof, easy way to fill is a challenge I imagine.
Let us know what works best.

MJD

My Feedback: (1)

The tubing I have takes a set after gently heating over a Bic flame, it seemed to hold okay on the latest run. Fur sure, I didn't make the situation easier with the fuel line location, but I was determined to clean it up somehow.

Pond Skipper

Mike its day 9 how's it going with your's come on ol chap, this one your going to finish and fly!

MJD

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LE "D-box" cap is CF tissue, and entire wing covered in light silkspan and given a couple of coats of nitrate before cutting ailerons free. Slot in ailerons capped with 1/64" ply forms socket for torque rod.

Tonight made the strip aileron linkages. Used 0.032 wire, for the horn I peened flat and soldered a short stub of 1/16" OD brass tubing. I have a stash of ~1/32" ID nylon tubing for the bearing, it fits closely but works smoothly with the wire.

Much scotch tape here and there while I sort things out.



I want my 3x3 props.

Pond Skipper

I need the patients to do this on my NANO II, great work Mike this is going to make a difference in speed.
I have made torque rods with scratched up ends and then slipped press fitted plastic tube with some CA
for the Skorch project flaps and ailerons they have worked very well no migration.
Going the extra step to solder them on may work very well. Good rosin flux and choice of solder wire
is key with plenty of heat. I hope they stay put! Man that tork'n rod is small lol woooooot!!!

I have the carbon 3x3 in the mail from Hobby King will report my findings.
They will not be as light as the cut down E-flite 3.75x3 nor as thin.
However with some reshape work and sealing back up they may have
some fantastic results and should last longer than the plastic props.

MJD

My Feedback: (1)

The wire is bent over and squeezed tight before inserting in the brass tube, and all dipped in acid flux before peening flat and soldering. I pulled a test article apart, without the bend over, and it was plenty strong. You can sort of see this affair in the last photo above, the brass tube is tilted as a result on both, but I made them symmetrical.

Honestly, the scratched wire and plastic tube will likely never fail.

Pond Skipper

Pond Skipper

Mike there is a machinist in Canada who had done work with .049 twins is interested
in doing a run of TD .010 aluminum back plates after seeing another machinist build one.
They are leak free do to no flex or heat warp nor stress crack at the bolt holes helps cool
the engine.

Here is a sample pic. Do you have a old loner case he can use as a guide, he is ordering
the stock back plate to reference for the build but needs something to fit and finish the aluminum
version too. His email is [email protected]

Custom building 049's
inline twin
http://www.coxengineforum.com/t3369-inline-twin
9 cylinder radial *out of planning stage, machining commencing soon*



http://www.coxengineforum.com/t9554-...backplate-part

Pics from MauricioB

MJD

My Feedback: (1)

Hmm, I might have. Pretty sure there is a trashed one somewhere.

I'll email the guy. I'd like a couple of smaller footprint backplates for these silly small models too. Maybe cylindrical equal in OD to the front of the stock plate and some other scheme to mount it.

MJD

My Feedback: (1)

Hmm, I might have. Pretty sure there is a trashed one somewhere.

I'll email the guy. I'd like a couple of smaller footprint backplates for these silly small models too. Maybe cylindrical equal in OD to the front of the stock plate and some other scheme to mount it.

Pond Skipper

His first thought was to just mimic the original but yes a lean mean back plate with less size could help
reduce the firewall size.

He may do the same for the TD .020 which would be a hot seller too. You may have seen the crack in the
first pic of the red plastic back plate this is common to happen if you have a old vintage back plate.

The radial mounts sold for the TD .049 than screw in could be similar just bolted on would have
minimal footprint if just enough dia. for the mounting screws or at least two tabs. In fact this style
would be faster to machine in just a few steps.

aspeed

The .020 one is harder to make because of the thread. At least with my stuff. I could whip up a few of them, but can't drill the holes, as my mill is without a motor for a while, and my shop is all f'ed up for a while now. My other mill is sitting on the floor with no table. My lathe is ok though. It is a turret lathe, so after one part, three or 50 is not too much of a big deal, other than cutting them off.

Pond Skipper

Both TD .020 and .010 use four bolts to hold on the back plate.
Just need 4 counter sunk bolts and 2 to 3 or 4 screws to mount to the
firewall.

aspeed

Oh. Thought that was a pic of the .02. I don't have one of them, just the reedy one.

Pond Skipper

Yea that was a .051 with the mounting tabs cut off and polished. So real simple back plate
could be made the main tolerance is the dia. of the inner back going into the crank case.
The hollow out area to save weight but could leave the inner wall thick enough to tap
a pressure fitting for anyone wanting to try pressure. Its a top hat but needs a lath to
get right.

Today I went flying and hit 168.86 kp h / 104.91 mph / per doppler
I had the existing prop a bit more narrow. Winds 6 to 8 mph.
Tested the 3x3 cut from the 3.75x3 it had great
thrust but speed was down in the low 90's

Mike I had to reduce rates down to 45% its about maxed out.
I tested first flight at 60% went vertical about 160ft. up jammed
in full right and down induced a fun flat spin that was hard to pull
out of in fact by the time I recovered the plane pan caked into the grass
no harm to the plane just a wake up call on the limits. Part of it was distance
away and height did it with the 3x3 vertical speed was great but alas the prop broke.
Micro silver and checker ball of blur with the throttle wide open.