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HelicopterMain Discussion › I'M BACK! AFTER a 2 year break and I still LOVE​HELIS!
07-07-2017 03:50 PM  4 months agoPost 81
EEngineer

rrProfessor

TX

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In AMA pattern, we use a fixed pitch prop, and "tune" this length for a fixed RPM.....by adjusting the pipe length where the pipe is attached to the header.

Using an optical tachometer....running up the engine to full throttle...on the ground....

The above is the theory behind "tuned pipes"....

Now for porting the header....and why it's important for the tuned pipe effect....

The header that is bolted to the engine has its output port smaller that the output port of the engine. You can see this y removing the header after running the engine a few times.

There will be "black" exhaust residue on the aluminum of the header flange....that exactly matches the size of the engine's output port. And this is the "trick" on how you can easily "port" your header to match the engine's output port size.

With a mis-matched header port, after combustion when the piston opens and gases are exhausted....a small portion is reflected back into the engine's combustion chamber....right at this junction.

Not optimal....you want it to be reflected back into the chamber as the pistons closes....not when it's opening.

If this junction is "matched" in size, the reflection at this junction is minimized.....and this is called "porting your header".

And it's very easy to do...and almost everyone has the tools to do it.....a dremel tool with a conical grinding bit(get the bit at Home Depot).

Remember the black residue I spoke of in the above?

Simply stuff some paper towel material into the header(keeps the grit from going into the header) and just "flare" the header port where the black residue is visible.....until no black is visible anymore.....

Then, your header's output port size is exactly matched to the size of your engine's output port....

Easy as pie!

Pull out the paper towel material....flush with water from the back end of the header to get the grinding grit out....and then put the header in your kitchen oven(set to 150 deg.) for 30 mins. or so...to make the water evaporate....

At this point, I would usually "lap" the header flange using some "wet or dry" 400 grit sandpaper and machine oil....on a flat surface(glass top table is perfect) to remove any "nicks" in the header flange where it bolts on the engine....for "perfect seating" when bolted back on....

And now, you have a ported header.

How to adjust the length of the tuned pipe baffle....for a heli tuned pipe is more complicated for a heli.....than it is for a fixed wing 2-cycle engine....as the header and pipe are combined into 1 unit....and because the blades(prop) are not fixed pitch.

But porting will add some RPMs....which is what you want..

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07-07-2017 04:18 PM  4 months agoPost 82
EEngineer

rrProfessor

TX

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If the manufacturers of heli tuned pipe/header assemblies could use a "baffle" which is bolted(a slotted baffle flange within the pipe with slotted bolt holes on the pipe exterior), the baffle length could be tuned to the heli engine's RPM range that you use.

At least that's my idea....

But, they don't, so just port your header, because it's so easily done...

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07-07-2017 05:00 PM  4 months agoPost 83
JuanRodriguez

rrProfessor

The Villages,​Florida

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Great explanations above, EE...... and put in terms so simple that even a caveman can understand them !! Nice job !

The tuned pipe concept is also applicable to racing go-karts..... they have a lever whereby the driver can actually adjust the length of the pipe "on the go" to optimize the power derived from the motor.....

Been there, done that and old enough to know better.....

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07-07-2017 05:07 PM  4 months agoPost 84
EEngineer

rrProfessor

TX

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A lever...wow...way cool....

Is that 2 position....or variable?

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07-07-2017 05:10 PM  4 months agoPost 85
JuanRodriguez

rrProfessor

The Villages,​Florida

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The ones I've seen are variable.....so you can tune the motor on the go...

Been there, done that and old enough to know better.....

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07-07-2017 05:12 PM  4 months agoPost 86
EEngineer

rrProfessor

TX

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That's really hi tech....and you have the tach right in front of you....

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07-07-2017 05:15 PM  4 months agoPost 87
EEngineer

rrProfessor

TX

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I think it could be done with heli pipes, too.

With an external gov. and telemetry, we almost have the tools to do it...

Just need the ability to move the tuned pipe baffle.

Even if it's done on the ground between flights...one can adjust to the environmental conditions.

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07-09-2017 12:26 AM  4 months agoPost 88
wifeorheli

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reno, nevada usa

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NOW YOU GUYS HAVE MY FULL ATTENTION LOL I'm ALL for getting maximum power out of my engine. EE can u post some pictures on where your exactly modifying the pipe? So I can visualize it... Also curiosity I have noticed pros don't use a exhaust deflector is this due to the exhaust has to travel further before existing the system? See this is why I love nitro so much more involved! Thanks for the comments keep them coming!

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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07-09-2017 01:16 AM  4 months agoPost 89
EEngineer

rrProfessor

TX

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In AMA pattern, you have a header that's separate from the tuned pipe.....connected by a Viton rubber coupler.

You adjust the coupler length to tune the pipe for the RPMs that you have for whatever diameter/pitch your prop is....using an optical tach to check the RPM peak....then back off a touch for when the prop "unloads" in the air....~1/4"

A heli pipe is one unit.....header and pipe all in one.

To tune that, you would have to identify where the baffle is within the pipe(probe it with a coat hanger)....and cut the pipe into two pieces just in front of the baffle.

Now, you would have to determine whether to shorten or lengthen the two pieces.....

If you go too short, you can always re-lengthen....if it's too long, cut off some more of the pipe that doesn't have the baffle.

The hard part might be to re-weld the two pieces together again.....or to find some Viton rubber tubing whose ID is the same as the OD of the heli pipe.

Viton rubber is ideal because it can withstand the high temps without failing.

If the right length is satisfactory, you could re-weld the two pieces back....to eliminate the Viton rubber coupler.

Another source of coupler is that used in 18-wheel trucks....like a "FreightLiner" supplier, etc.

You just have to find the right diameter....and probably buy it in much greater lengths than you need.

But I didn't give a hoot about that....I just needed the product however I could get it.

Also, realize that the "back end" of the pipe must be supported on the heli frame.....as the failure point is right at the header flange that bolts to the engine....

It would happen often, because we always "soft mounted" the engine to prevent excess vibes to the airframe.....no big deal, as I always carried spare headers that were already pre-ported....just in case.

The exhaust deflector has absolutely nothing to do with the pipe tuning.....it might restrict the exhaust a touch, but I always used them....because I don't want exhaust gunk on the airframe.

My engines were mounted head down...and were rear-exhaust....and the pipe was routed within the airframe interior...with just the exhaust deflector protruding downwards and out the airframe......less aerodynamic drag that way.

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07-09-2017 04:44 AM  4 months agoPost 90
wifeorheli

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reno, nevada usa

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Thanks for the response I see zero pros using them and it's little things lime that I notice and always so were why they dont... If you could give us any pictures showing me exactly where to grind. I'm think g your talking about where the header meets the pipe not the end that hits the engine itself?

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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07-09-2017 05:01 AM  4 months agoPost 91
EEngineer

rrProfessor

TX

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Porting the header?

Yes, where the heli pipe bolts to the engine....there is a flange, with a bolt hole on either side of this flange(perhaps slotted bolt holes) that mates with the exhaust port of the engine.

Right?....

Now, unbolt it from your engine and take the whole thing off.

Having done this, look at the engine side of that flange....it'll have black residue on it....in the pattern of the engine's exhaust port.

(If there's black residue totally covering the engine side of this flange from use...maybe leakage too..."lap" that side of this flange using the technique I posted earlier....to remove all the black residue....then remount the heli pipe...run the engine a few times....then the pattern to grind will become clearly apparent with the new black residue from a couple of engine runs).

Then, using your dremel tool...with a conical grinding bit(get one at Home Depot)......grind where this black residue is..."flaring" it into the heli pipe mounting flange smoothly...when the black is gone, the engine side of that flange matches the dimensions of the engine's exhaust port.

This black forms the pattern where you grind....to exactly match it to the engine's exhaust port....with your particular heli pipe.

The result is that you've "ported" your heli pipe.

This part is easy.....tuning the baffle is more difficult.

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07-09-2017 05:16 AM  4 months agoPost 92
EEngineer

rrProfessor

TX

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I can't seem to find any decent pics.

Other than idiots hacking on their engines, rather than the "header"....

DO NOT GET A DREMEL TOOL ANYWHERE NEAR YOUR ENGINE...PERIOD....!!!

The grinding is done ONLY on the mounting flange of the heli pipe.

And, I forgot to add.....

After you finishing the grinding, you'll want to get a "polishing" bit, too.

"Porting AND Polishing"....

The grinding to match the pipe's mounting flange to the engine's exhaust port will leave the aluminum inner surface of this mounting flange somewhat rough in texture.

Use the dremel tool with a polishing bit(and some machine oil) to smooth this rough texture....i.e. polish it....

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07-09-2017 05:35 AM  4 months agoPost 93
EEngineer

rrProfessor

TX

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It's been my experience that the manufacturer of a header purposely makes the exhaust port smaller than that of the engine.

So that the header is "universal" to a variety of engines.

And that the end user will be able to "port" it properly....as I have attempted to describe.

Here's a link to some pics of some Hatori Headers:

https://www.google.com/search?q=hat...iw=1280&bih=546

See that oblong hole on the header at the top left?

That's the hole that you want to grind to make wider....and "flare" to match to your engine's exhaust port hole size.

You have the thickness of that flange in which to "angle" it in.

Afterwards, just polish that inner area where you ground the aluminum material off....

More clearer now?

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07-09-2017 05:42 AM  4 months agoPost 94
EEngineer

rrProfessor

TX

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"I see zero pros using them "

How would you know.....unless they pulled the heli pipe off and showed you?

It's not visible when your heli pipe is attached to the engine.

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07-10-2017 09:20 PM  4 months agoPost 95
wifeorheli

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reno, nevada usa

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Meant zero pros using a exhaust deflector. Was curious if it changes tune having more length before the exhaust exits...

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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07-10-2017 09:24 PM  4 months agoPost 96
wifeorheli

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reno, nevada usa

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EE THANK for elaborating I get it now I have a few extra pipes time to bust out the dremmel I'm very Interested in seeing a performance difference!

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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07-10-2017 09:36 PM  4 months agoPost 97
EEngineer

rrProfessor

TX

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"Was curious if it changes tune having more length before the exhaust exits..."

The deflector has absolutely nothing to do with tuning.

It's only purpose in life is to try and keep the exhaust gunk off...

And to add weight....

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07-10-2017 09:48 PM  4 months agoPost 98
EEngineer

rrProfessor

TX

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"I'm very Interested in seeing a performance difference!"

Remember....port the pipe and then check....without changing anything else.

So your measurements will be accurate....

You must use a tach....or some other device...what you perceive is not an accurate way to measure things.

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07-12-2017 09:24 PM  4 months agoPost 99
wifeorheli

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reno, nevada usa

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SUCCESS! HV setup complete and flown! Step down on governer throttle with the futaba ps01. Truthfully I'm not Impressed. Don't really see a major difference from my other setup. I'm gonna mess with the roll rates ect... but I was under the impression my heli was gonna be super charged! I mean 400$ in servos....

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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07-12-2017 09:25 PM  4 months agoPost 100
wifeorheli

rrElite Veteran

reno, nevada usa

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Comes out to to 4 flights on pulse 2550mah battery so they don't suck to much power

Novarossi Motors U.S.A
www.PlanetHobby.com
Team Align
GrandRc.com
ZRC U.S.A. "PushGlo, SwitchGlo"

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HelicopterMain Discussion › I'M BACK! AFTER a 2 year break and I still LOVE​HELIS!
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