MJD

My Feedback: (1)

I think there is very little history of running the bejeebers out of the .020 and .010 size, so nobody really knows where they get fragile. The AMA payload guys likely know a thing or two about .020's but not sure they rev them to the moon.

According to some quick dubious math, the piston speed on a TD .049 at 24k is the same as an .010 at 41k. That's one factor, now for the other 14 or so..

combatpigg

My Feedback: (3)

The rod length to stroke ratio affects piston speed too.
Some ratios favor more of a smooth constant cycling with a short pause at TDC / BDC and other ratios cause the piston to loiter at TDC / BDC and then get suddenly yanked.

combatpigg

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At 600 cycles per second how many feet does a .010 piston travel...?

MJD

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600 rps x 0.226" stroke x 2 = 271 ips = 22.6fps

I think.

Pond Skipper

Already seen 42K rpm / 700 / 26.37 fps

Crazy as I am shooting for 45k / 750 RPMS / 28.25 FPS

Imagine if the best materials and bearings where in the mix.
Could:
- Lighten the inside of the piston skirt
- Make a new crank case for bearings
- Integrated venturi for zero chance of air leaks.
- Remote Finer needle / thread for max tweaking.
- Remove the cylinder's steel fins and lower skirt, press fit an outer aluminum sleeve with fins.
Could keep skirt to allow the cooling shell to be rotated and locked in place with the glow plug.
Would allow aligning a single port exhaust with footing / threaded for 1.5mm bolts to hold a
muffler type or header pipe for goo control.

- Aluminum back plate with pressure tap with 3 tabs for mounting to stabilize any remaining vibrations.
- Titanium prop bolt with integrated small low mass spinner / none threaded area to improved centering of the prop.

- TD .010 - 50K / 2x3 / 142 mph

combatpigg

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It would be handy to test engine / prop ideas with a little wind tunnel.

MJD

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I tried getting my Profi .049 to stage by hitting it with a leaf blower.. the package says it gets up to 200mph exhaust velocity.

combatpigg

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I did the same with a leaf blower, hitting the running engine from all directions and it was interesting to listen to the reactions.
looking back on that session it would have been smart to fit the engine with a foam air filter.

combatpigg

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26 FPS is pretty amazing when you consider the piston isn't just sliding back and forth freely with no resistance but it's working to get that 26FPS.
This is what it so miraculous and underappreciated about small engines.

MJD

My Feedback: (1)

The piston speed isn't out of this world, less than a 302 at 6 grand (F1 is up in the mid 80's fps AFAIK, F2A speed in the 60-70 fps range). But every tankful of fuel is about 40,000 cycles on a bushing based engine so 25 tanks is about 1,000,000 cycles. So yeah, you gotta have some respect for the simple design and the resulting service life!

The thing that amazes me when I think about it, is the insane level of dimensional precision to which the small Cox engine grinding operations were done.

Pond Skipper

Last flight the NANO did 5.49 mins. of running say average rpm 38k / 219,766.7 revolutions
one tank of gas. I have lost count of the flights would imagine I am around 40+ flights now
So far around 8.79 million revolutions... lol cwazy...mang...

combatpigg

My Feedback: (3)

Now that we're talking piston speed, I've answered a question that has come up while considering which stroker kit to get for a 351 engine.
The 302 is the 351's little brother with a 3 inch stroke. 6000 is nothing for these engines.
The 351 has about 3.5 inch stroke, so as you can see the higher piston speed will limit rpm more than the 302.
There are stroker kits for the 351 that create a 392, 408, 418, 427, 440 and even a 454.
It's mainly done with strokes over 4 inches and with custom rods and pistons.
The greater the stroke, the shorter [and less stable] the piston will be.
True to most other lessons in mechanics the most exaggerated combinations give the least service life.

MJD

My Feedback: (1)

Yup, 7000 is 3500 fpm, I think that is the usual limit for cast pistons when you care.

combatpigg

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It appears the most popular dual purpose stroker combo for 99% street / 1% strip duty is the 408 design.
It's almost "square" with a 4 inch stroke and 4.xx bore.
If you don't give it bigger heads, exhaust and intake it puts out basically the same power as the 351, but at a lower rpm...so as the saying goes "when you change one thing you really must change everything."

Pond Skipper

Mike Mike Mike .. what up mang you fly the lil beasty yet?

MJD

My Feedback: (1)

A minor roadblock.. After a week biz trip to Germany I was at the office for a day, then had a crazy sweaty/dizzy spell and got hauled into hospital. I'm currently holidaying in the cardiac ward, tests tests to determine the cause of a recurring low heart rate. I've had a few weak spells before, but this one took the cake. I'm in decent health and shape but this might some congenital thing, or who knows. Will find out soon enough..

Pond Skipper

Glad to hear from you Mike, was wondering about you.
Happy to know you are in there getting things sorted out!!!!

I take a low dose aspirin each day and CoQ10 for the heart with a daily vitamin in hopes of some
preventive action towards the alternative. I hope you are able and well soon as possible with a
solution. Take care and keep us posted we could all learn a thing or two from what you are going
through. Best wishes!!!!!

Brad

combatpigg

My Feedback: (3)

MJD the obvious is for them to monitor your blood sugar..and for you to monitor your levels during the day if nothing else is conclusive.
Exhaustion from long term lack of sleep because of pain, tinnitus, apnea, etc. can trigger episodes of low sugar.
MDs might disagree.

MJD

My Feedback: (1)

The paramedics checked when they picked me up, it was fine at 6.8. My older son is type I diabetic, I checked with his glucometer during a previous episode - I was definitely thinking along the same lines as you - but doesn't seem to be the case. Had an echocardiogram today, tomorrow a stress test and another scan I can't recall.

Pylonracr

Mike
I hope you are doing well. I was getting ready to yank on your chain for not getting back to me on the performance of the carbon fiber pipe. I guess I need to cut you a very small amount of slack since you came up with a fairly good excuse...........

Get well soon

Scott

MJD

My Feedback: (1)

Yeah, the abuse level here is pretty high, hard to retain any sense of dignity or self-worth..

Everything on hold for a while and behind, but I returned to work this morning. I know you're anxious for numbers, I'd like to see them too!

The .67 is mounted up with the Mac pipe and ready to go. Next trip to the hangar (any day) I'll do some bench running and comparison. It's too loud for my back yard in the village.

Cross Check

Glad to hear you are OK, Mike,

I have some twezers with fuel tube on the ends. I can launch the Q45 for you !
Sweet project !
Also, rubber gloves so the Toucan does not 'squirt out my hand like a mellonseed'

Look foreward to flying with you again.

EF-1 PylonRace near Grand Valley coming up. I'll be in the area. A Sunday I think.
( I want to try my OSFX.25 Maac Scale Combat Spitfire, I know well, around the course. It will be weird flying 'around' myself) (elastic control line?)
I'll drop by some brewery wares for Maralyn Crew.
Hope to see/fly with you when....

Dave'crosscheck'Fallowfield

MJD

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Cool, I'll try to make the EF-1 race or at least drop in. That's really close to the hangar. We're at the Base Borden airshow this weekend with the Moth though.

And I need to get that combat plane going so we can go crash together sometime.. I'll skip the .50 and go with something more sensible

Pylonracr

YO Mike, Still around ???

Hiding?

MJD

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No not hiding.. had a really crazy last 2-3 months. Health issues (all good now, but was hauled into the cardio ward for two nights, then two weeks off work with many tests), managing $%@# packaging line installation projects (1 finally done.. yay), finishing deck so we can use it this year (all done last weekend.. yay), repairing hot tub (not done, boo), and still finishing Tiger Moth minor issues (some done) and readying it for airshows and fly-in season. Just putt-putted home from Geneseo NY air show yesterday.

I ran up the OPS on the MAC pipe and bench prop 4 times a few days ago, rich 2c and working up to full tilt, seen 22,000 so far but there's more to go. I machined a .410" ID phenolic stinger for your pipe as the outlet ID is pretty big - I suspect this may help performance. So after an interminable wait, I'll have some news for you pretty soon now. Hopefully this gets done before those tips arrive.. :-)