Tee Dee Performance Crank

I have not adjusted the header yet waiting on some 7mm ID silicone tube to arrive in the mail.
First effort here was to simply use the Profi pipe and its tuned proportions from the belly of the pipe
to the end of the header less its coupler I cut off.

Pipe design proportions stay consistent (header, belly and stinger) but you can use a larger belly for more torque to a given degree. Given the stinger length is pretuned for the Profi .049 as you know the rpm range is greater per its engine design. I was curious how the belly size would effect the engines torque. My previous open exhaust cox engine readings in relation to the numbers with the pipe and cox car engine muffler shown suggest power has been boosted. I have noted rpm loss with the cox muffler over open exhaust, given the pipe in the mix I should loose more rpm if the pipe wasn't helping or functioning at some percentage as a tuned pipe. If the header section is too short the engine will overheat, during the testing the engine was running at normal observed temps as an open exhaust engine.

Today I did another test - first test was to discover max rpm- 1 shim 21,610 secondly I check the torque simply by attempting to stop the engine pinching down the spinner at idle I tried twice and wasn't able to the torque is much stronger than open exhaust in that state I am able to stop the engine. 3rd establish the idle and insure it's stable so I can go fly. I plan to add one more shim and go fly  

Note the Profi .049 pipe has a mid range length stinger the ID is 3.15mm with an exhaust port ID of 7.5mm. With the above stated proportions the restricted square shaped Cox buggy muffler being used as a header adapted to the engine the area is reduced 4mm x 3 mm for an average of 3.5mm respectfully and unfortunately reducing the the pipes ability to function at its best. In the long run I plan on fabricating a better engine header consistent to the 7.5mm ID pipe and cut it down / tune from there. For now simply adding some 7.5mm aluminum tube with the silicone tubing on order will least let me explore the header pipe length range needed when I construct my custom header / engine adapter.

Extended header pipe total length 10.75in dropped rpm down to 8.559k -9.5k average.
The top end 19,622 90% best needle 1 shim rpm is less than the original set up.
Using some additional aluminum tube and forming it to go from round to square I have a transition to the cox exhaust deflector.

I noted that total pipe and header length at 11.25" was increasing low end and decreasing the top end.
For swinging a 6 x 3 the added torque may be worth it.

Tried low compression glow plug on one shim this resulted in lower rpm and idle with just the pipe and cox deflector.
Final results less rpm but sounds good and idles lower, best rpm is the pipe and cox exhaust deflector on its
own in the previous vid.

Nice sound lower idle with the extended header pipe:

Ok its really getting down to the fine tuning now as it must. The Cox buggy muffler is still being used by it has to be understood how its affecting the system by lieu of the square transition and choke down from 7.5mm to 3.5mm. It acts like a anti -reversion zone limiting back flow of exhaust gases back into the cylinder fooling the pipe in thinking its longer than it is. How much will be known as the numbers come to light in the testing. The 7mm silicone came in so I can move forward now with a fast simple was to adjust the header length to suit the engines rpm range with a given selected prop. Using a timing deg wheel it is apparent the exhaust timing is at 120 deg. The goal is unloaded at 23,800 rpm with a APC 4.5 x 4. The current physical header length as shown in the pic 8.5
Given a section is part cox muffler acting like a anti reversion zone my guess
I am actually at around 9in.

Found another formula seems to provide reasonable pipe lengths

The deg wheel shows the .049 to be at 120 deg.
120 x 1700 / 23800 (unloaded est. goal) for pipe length of 8.57

So looks like the silicone adapter will get me where I need to be unloaded with either the 4.2 x 4 or 4.5 x 4
So next test with the 4.2 x 4 static which will help give some idea how close to a unloaded 4.5 x 4

You can now determine needed rpm window for a 9in system as an option
120 x 1700 / 9in for 22,667 rpm / 4.2 x 4 the engine should make near that as I have already seen 1st vid recorded at 20,996 rpm with the 4.5 x 4 so tonight I have slapped on a 4.2 x 4 and will take some readings if it gets those numbers static I can take a 1/2 in down and fly with the 4.5 x 4
for a potential 23.6k to 24k unloaded in the air. Will post a bench test vid and look forward to posting a flying vid this weekend.

Ok tested simulating unloaded rpm to tune the pipe here are the results

APC 4.2 x 2
120 x 1700 / 24,063 for 8.4777459 (think Im a bit over revved engine was hot as the pipe
wasn't keeping up header and with anti reversion est. 8.75
- next will try a 4 x 2.5 to simulate the APC 4.2 x 4 unloaded

Need 204,000 / 8.75 for 23,314 rpm so 4.2 x 4 for 88.3 mph

I'm a little lost in all the numbers now, is that a 4.2x4 prop at 24063rpm?

That would be about 66W of power, according the Pe Reivers excel sheet. So pretty standard for a .049 engine I guess. You might want to take a look at the power versus rpm curve, it seems rather flat at these rpms for that engine now?

In that case you are better of by making the same power at a lower rpm I think.

I was simulating unloaded rpm at 24k with a APC 4.2 x 2 the idea is to run on the pipe at full throttle and determine the rpm range per the selected length.

Yes the pipe design does help produce more torque as noted in my previous observations. I had mentioned before a 6 x 3 prop could take advantage of this. I plan to try a APC 5.75 x 3 at some point I think its possible the pipe will allow more rpm's then a open exhaust TD with the greater dia. props. I had noted the torque was so strong I couldn't stop the engine at idle by pinching down the spinner yet with open exhaust set up with the same carb I can.

I want to simulate the unloaded 4.5 x 4 in the long haul the prop fits the Skorch's weight and size.
Looking for 23k with the 4.5 unloaded on the pipe.

On 25% nitro the Killer TD with RC carb can hit 24k+ unloaded with the 4.5 x4 prop. A stock non RC TD can do 24k unloaded much but not static. So the pic is static with carb 4.2 x 2 simulating an unloaded 4.2 x 4

Ideally you would want the engine to make the highest power at the unloaded rpm in the air. So you would match the prop-load to keep that rpm in the air.

Spinning a 4.2x2 at 24063rpm static requires about 35W, so that is the power that the engine is actually making at those rpms, i.e. about a factor of two lower than most other .049 engines. I think you would benefit from making a power versus rpm plot to see at what rpm the engine makes the most power.

Why have you decided to run it at around 23000rpm?

I used the smaller load during bench testing to get on the pipe to confirm the pipe length / rpm relation for unloaded flying later. Additionally I needed to review fuel draw / waste, engine heat and to check and make sure the cox muffler adapter effect on pipe length is understood and can be accurately sorted out during prop adaptions and pipe length changes.

The goal of being in the 23k range is to keep the wear off the ball socket and to use the pipe length that
suits that range. I know how the plane performs with the 4.5 x 4 at that rpm range.

Will take the engine apart next to improve the intake of the cox muffler section for better uninterrupted flow to reduce the anti reversion effect.

When you take it apart are you going to ck. the Ball Socket at this time ?

Yes I checked the ball socket last night it was still good surprising enough.

I added some timing shims (2) to the TD .050 I am now at a respectable 170 deg duration- no copper shims on the head with a high compression plug I have usable compression for 25k unloaded flight . To compare it snaps over like a broken in engine.
And now the math for pipe length from center of the converging cone zone to the piston some say center of piston some say at the side. If at the side you may assume the pipe is a hair long worst case. For me this pipe design will give better torque as it already has shown in previous tests.

I am now forced to use the 4.2 x 4 do to the 170 deg duration to keep a reasonable length of pipe down the fuselage and rpm in check.

170 x 1700 / 25000 rpm for 11.5in subtract the reduced area of the cox muffler acting like a anti reversion zone
- my guess I am actually needing around 10.5in - set up is now at 10.5in actual now ready to test
- will post static results simulated unloaded flight with 4.2 x 2 - 25k rpm for (4.2 x 4 unloaded 85-95 mph)




Here is how I block one exhaust port, thin brass sheet stock trimmed to sit inside the groove of the muffler, blocks off the breather hole too.

1/2A Nut wrote:
I added some timing shims (2) to the TD .050 I am now at a respectable 170 deg duration- no copper shims on the head with a high compression plug I have usable compression for 25k unloaded flight . To compare it snaps over like a broken in engine.

The cylinder "timing" shims will usually only change the timing by a few degrees. You can use the same trick on almost any engine, but the change is very small without any rework on the exhaust-port itself.

Are you saying it went from 120° to 170° with the addition of a few shims?
It just doesn't sound possible to me...

After the engine was torn down for inspection I was able to check the engine - my other reading was with a stock TD .049 at 120° deg duration.

This engine with the performance crank: 140° degs of duration
exhaust cycle begins 110° degrees after TDC and then it re-closes at 110° degrees BTDC


After using two timing shims - took away 1.2 turns out the cylinder threads
exhaust cycle begins 95° After-TDC and then it re-closes at 95° Before-TDC
170° of duration.

Will run it up after work and see how the engine responds.

Back in the day Dale Kirn was making these mods:

This is very interesting to me. Lots of variables.. (ha ha.. as if there weren't enough with Cox engines to begin with..) When you change/alter your timing-shims.. the single exhaust port indexes in a different position in relation to the "fixed-position" header? I don't have much engine knowledge and maybe I missed something in the thread.. but is this why you are blocking one of the exhaust ports?

Have you thought about bringing the header and the .05 cylinder to a local machine shop, and have them give you a quote on machining a header having a round exit-pipe bore; equaling the total (dual) exhaust port area? It would seem to me that this would make tuning the pipe easier; while also allowing the cylinder to breathe as designed. Maybe even use a dremel to grind a radius into the header (inside) to improve flow? (sort of like "extrude-honing"   )

http://extrudehoneafm.com/

I'm just throwing this out there.. as food for thought.

Current set up for next test

Yes Roddie I had to use two shims to get the cylinder back around facing the same exhaust port to the header. It actually worked out nice as it gave me 170 deg timing. A longer timing duration will allow the boost charge to shoot into the cylinder at the right time.

You have 3 components working here gas charge, heat wave and sonic sound wave. I have bored out the cox muffler to increase flow but yes would be I have some future options for now this is what I have to work with. The tuned pipe is like a pump it pulls fuel and air thru the carb any excess is stored in the header area and boosted back into the combustion chamber if you have the pipe length / rpm ratio and engine timing correct.

[quote="1/2A Nut"]170 x 1700 / 25000 rpm for 11.5in subtract the reduced area of the cox muffler acting like a anti reversion zone
- my guess I am actually needing around 10.5in - set up is now at 10.5in actual now ready to test
- will post static results simulated unloaded flight with 4.2 x 2 - 25k rpm for (4.2 x 4 unloaded 85-95 mph)




quote]

'/"A Nut what is the rule of thumb to tune an exhaust pipe? Suppose I have a non-SPI 050 cylinder and the same pipe as you have, what am I suppose to do when slipping the exhaust to and from in the sylicon extender to catch the tuned-length? Just listen o the tach variation at full throttle and select the highest rpm?

There is more info on RCU but for now

For Cox TD you want:
- Know the formula
- stock exhaust timing is 140 deg x 1700 divided by rpm gives distance from the center of the cone to piston face.
  (if you goal is 23k unloaded with a 5 x 3) 10.35 inches or 26.3 cm if you want to play is safe add more header length
   and cut it down till the rpm no longer increases. You can opt to back off a bit and let it unload in the air.
   Set the needle a little rich the first dive will pop it on the pipe your good from there.
   Note that pylon racers start off on the pipe on the ground a bit rich it will lean up in the air.
-  you must modify a stock cylinder with just bypass port no boost flutes.
-  follow this pic the blue is the piston going up the red is filed away to increase more boost at the last moment
-  you can use a buggy muffler as is - find one with no breather hole or one with of the generation type that has a
  very small pin hole in the end they has rather large bored out breather holes if so then you much shim like in the
  pic blocking out the breather hole you can use up to 1 timing shim max. Look closely at the previous posted pic
  I used thin brass strip in the exhaust channel. If you do this only file the cylinder side facing the header pipe.
-  use a pressure tap on the header or on the pipe at it apex center of the cone if you have a threaded two piece
  pipe it is best to tap a small fitting at the collar to stop the pipe from un-threading in the air.
-  any silicone used must be supported by aluminum tube you cant let it expand and contract under exhaust pressure
  it will throw off the timing of the pipe.

This is what I know so far in a simple direct manner - you must understand the function of a tuned pipe and if you follow
this method you will have a pipe that does work well enough to carry its weight in the air or well enough to have less loss
if you want a neat sound and oil spray diverter and cool look. If you can machine a good manifold then you will gain much
more performance over using a simple cox buggy exhaust diverter. I plan to find a better one for my engine when possible
I need a machinest to help me do up something simple in aluminum. 7mm ID for the pipe and 14.8 ID for the cylinder.


Red is the filed area / blue is the cylinder going up to close during the combustion cycle. One or both sides depending on your coupler. Do not harm the fins~






Watch this best animation on the web click the OK to move forward through the cycle processes.
Also shows what happens when the timing is off fast and slow

https://www.bukupower.com/animatecorrect.html

Thanks a lot 1/2A Nut, this is a very useful explanation, and I like the animation. The principle of the tuned pipe operation was known to me, but the visualization by the animation is just perfect.

Given that the cylinder conversion you described is far beyond my capabilities, I will probably not venture into this, unless you confirm that even without the exhasut port and bypass flute modifications some performance ramp-up result is expectable with the tuned exhaust.

I slid you a greeny and your posting definitely deserves that and even more...

Thank you for the greenie I never get many lol weeee 


You don't have to mod the bypass ports - no shim needed if you use the simple cylinder with no flutes there is a bit of a gap between the bypass port and the top of the exhaust port / not much though you have to open it up a hair per the pic to get better use out of the pipe. I simple fine file and some tender care is all that's needed. Otherwise its a fancy muffler slash goo deflector with a neat sound but would be nice to have it boost a non SPI engine enough to at least offset the weight of what is already a very light weight pipe. I am getting very close to a full functioning set up that is usable with my Skorch I had the timing way up to 170 this was causing me to use a long pipe set up and I didn't like it. By going back to 140 deg the duration is shorter so you have to flare the top lip of the exhaust port and open the actual gap up a hair bit to help. The pulse is very strong it will force a charge back into the cylinder. I will allow a reasonable usable gain.

Watch this video of the engine crawling up on the pipe as the pipe is a bit long in this vid but also because the gap is so small it took awhile for the charge to boost in more rpm. The wing will start to wobble as it comes up on the pipe from 17.7k to 21.56k

Hi Balogh doing a follow up as to where I am with the Skorch tuned pipe quest I have a video:

Flew for 5.18 mins / 1oz tank, then after multiple knife edge passes I snapped the vertical fin off.
The tank had about another 30 seconds of fuel.
Set idle little high for throttle chops in the air - 7.8k rpm and still learning whats possible on pipe pressure.
Noted so far 24,793 rpm on the pipe APC 4 x 4.5 / 94mph tuned length for 25k unloaded.
Passes where consistent it is locked in on the pipe (9.8in) from center of the convergent cone to the piston face.
I need to shorten a hair more to be in the 25.5k range about 9.2in might do it.
Needle set to running with a reasonable plume of oil out the pipe as it was hot today 91F / with a heat index of 96F
Didnt want to risk overheating the engine or a dead stick - needle was set make the pipe chime on the ground.
Winds about 8-9 mph small gusts to 13 mph. 20% castor 25% nitro. Two shims now as of the current hot weather.
Thread reference for parts:
http://www.rcuniverse.com/forum/1-2-1-8-airplanes-70/11602404-ply-rolled-fuselage-part-deux-1-2a-mini-skorch-26.html
Profi Pipe with Sportswerks Header Pipe bolted on the same way as the Norvel Litemachine exhaust throttle muffler.

Hi 1/2ANut...it is fantastic. The title of the video suggests you have changed the engine to an AP 061? I could not clearly figure out if this was still the COX TD instead.

Regarding the tuned pipe: is this 9,7" length to be measured between the the piston face and where the tuned pipe cones (the diffuser with the converging cone) meet? Any chance that if I simply cut it to such length it will work properly, or, changing the length will change the wave length of the gas column and simply set another tuned rpm?

Could you possibly quote again the internet address of the tuned pipe vendor?

Once again, this is gorgeous, congratulations.. I have a similar project involving the Little Roughneck that I currently drive with a 051 reedie, and plan to change it to a TD 051 providing the built in nut spacing in the firewall allows the TD mount to be fixed.

Thank you

Thank you I thought you would enjoy it

Send Alberto a message on ebay:

Profi 1/2A Pipe:
ALBERTO CABALLERO, FLA / USA
Ebay contact; speeddomingoe
http://www.ebay.com/usr/speeddomingoe

Header pipe is a Sportwerks .050 header
http://www.ebay.com/itm/Sportwerks-SWK4122-Header-or-Manifold-for-1-16-Buggy-Chaos/391172498721?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D31965%26meid%3D84fc369fb376411fb0531b183dd2a8ac%26pid%3D100011%26rk%3D1%26rkt%3D10%26sd%3D351401117237

145 deg timing so
145 x 1675 divided by rpm that you think the engine can produce to sort out the pipe length.

Here is a pic showing where to measure pipe length you can follow the red line.
Center of the divergent cone to piston face.