DagTheElder

MTK

I will try to come back with a condensed explanation later today.

Regards

DagTheElder

MTK,

First, the axis in the figure is Time on the vertical axis and lenght on the horizontal axis.

The exhaust pulse (A) is seen to leave the port and to propagate toward the atmosphere, primarily sending suction refrelections (B) back toward the engine from the diffuser , and compression wave reflections (C) from the tail nozzle. The density of the shading(difficult to see in copies)is intended to represent superposision pressure, where the more dense the shading the higher pressure. In an optimized design the primary reflection behavior ensures that the peak of the suction reflection returnes to the exhaust port around the bdc period to aid the scavenging and induction process and the plugging pulse returnes to the exhaust port in time to hold the in the fresh charge and enhance the charging effiency, before the exhaust port actually closees.

The picture of time and distance is one which will remain similar in all engine speed, therefore it is the crankshaft timing points which move on the vertical axis as a linear function of the engine rotation rate.
As commercial tuned pipes do not (usually) have a diffuser build in, the comparison will be between a straight pipe and a purpose built pipe where the engine design parameters are reflected in a purpose build tuned pipe.

One method available to extend that band of speed downward over which the plugging pulse would provide a significant gas trapping action is for the pipe to remain the same lenght dimention physically but for the exhaust opening port to be redused at low engine speeds by a valving mechanism.

Well this is brief but hope it contributes.

MTK

Thanks Dag,

Very interesting. Curious if we were to put a hole or two in the header and venting that to atmospheric pressure, if that would disrupt the pressure fronts too much. Before pumps and such, in a way we used to do that whenpressurizing the tank from a pipe nipple; but that was more of a closed system. Come to think of it, it didn't make of a difference to tuning.

I probably won't do much else. I installed an exhaust diffuser on the stinger of the pipe. I'll see how that works tomorrow.

MTK

I changed to a 19.5 x 11.5 PN apc yesterday. Alsoinstalled an exhaust diffuser on the exhaust stinger tube. Both worked great; the jump on pipe is easily manageable

The sound in the air got even lower, more like an electric driving a gear box.....Really cool

EDIT: Dag's idea of valving the exhaust stinger at lower speed may be easy to actually do if the exhaust stinger is made of soft silicone rubber tube. In a way, that's what I did earlier on Dean's suggestion to reduce the exhaust area by constricting the stinger, except this wasn't a controlled situation. Rather, I reduced the exhaust area about 60% but it was constant from full rpm to idle.

MTK

Just received a canister exhaust set-up for the 30cc class from Mile High RC.

Came complete with a stainless steel convolued flex header and canister, and teflon coupler and spring clamps. It was surprisingly light at 8 ounces, everything included. It's a couple ounces heavier than the carbon pipe and ally header but not terribly heavy as some canisters. Price was lower than the Hatori header alone. All up, 75$ incl S+H

How it works will wait to be seen. If it boosts a moderate amount (less than the pipe but passable), is able to haul the current props and isquiet enough, then it would have been worth it

MTK

I just received the DLE35RA engine. It's rear exhaust configuration making it much more suited to Pattern applications.

Took a close look at this beastie's from the outside. I really like what DLE has done with the front bearing boss of the crankcase. For openers, it has the same diameter as the prop drive washer. This will make nose ring installation a snap

You might have picked up that some engines, the OS included, have a larger prop drive washer than the front bearing housing boss which necessitates prop drive washer removal to install a one piece nose ring. This hasn't been too big a deal but it requires woodruff key installation as the prop driver is installed

Another very nice touch by DLE aimed directly at the Pattern Market istheir machined front bearing boss; it's perfectly flat the way we have been used to from OS and YS.

Another rather interesting bit is the smaller carburetor venturi than other 30cc class gas engine. Obviously aimed at smoothening throttle response in piped application. I haven't taken this engine apart yet so I don't know what it looks like inside. So far, I like what I see.....

ghoffman

My Feedback: (3)

Here we go again! My poor old EF 78 Extra has had the SAP, a Hacker electric, a Mintor 38. Now I am thinking of the OS 33 with a pipe. So, what header length, ES 30G or -40?

MTK

You won't go wrong....That's the true ticket on that airframe. Sure, not as powerful as the DLE55 I played with but with 25 pounds of thrust, it's got the most beans in its class.

Header length and pipe length the same as all other 30cc class set-ups. Either the 30G or the 40G. OR a canister

MTK

Okay Gang, Auggie was kind enough to video my Aesthesis/OS33GT/ESComposites 40G pipe combo. The main take away is the noise level from that well tuned and run-in combo. There are places where the wind drowns me, the geese drown me and a full scale flying a couple miles away does the same. The engine has around 13 gallons through it so far, well over 200 flights. When she's finally well broken in, the bearings are super slick. Compression is high and power output terrific. There is never a need to go to full revs in any part of the AMA Masters Pattern sequence....

Here's the U-tube link http://youtu.be/iAd8dRxtNbQ...Enjoy!!

I think I am done with this thread. Time to move on

airborne2.4

Wow the OS 33 is sooo quiet.

MTK

That was precisely my point in doing the video. Just writing the words here didn't give folks a frame of reference. Just a quick listen will tell you all you need to know. Gasoline engines do not have to sound like the gas engines we have heard at the field over the years

The great thing about the set-up is that it is doable with off the shelf components. Even the soft mount is a item that one can purchase either from Merle or from me. BTW- the tank I show in the video is something put together from a Fiji water bottle and fittings I sell. PM me if interested

OS33GT
ESComposites 40G pipe
Dave Brown Hush Clamp pipe mount or similar soft mount for the pipe
Hatori back to center header with a small extension from a broom handle. Tuned length 27" from exhaust flange to baffle
Soft mount
Apc 20x10.5, 20.5 x 10, 21x10, Mezjlik 19x10 3 blade carbon

Couplers...Macs silicone works okay for 30 flights. Turbo hose works okay for maybe 100 flights. Teflon works okay but tends to leak. Or the best around are the ceramic fibre types I make. They are a little pricier at 10 to 15 depending on shape.but will last several 100 flights

airborne2.4

Thanks MTK!
I noticed you also posted some info over here http://www.rcuniverse.com/forum/m_10...m.htm#11322173

MTK

I've got some news I wanted to share. Ed Skorepa sent me a bunch of carbon canisters to play with on the OS33, DLE35RA and DLE55. As I develop findings, I will post here and elsewhere as appropriate.

I've been able to tone down the pipe jump at 4K, however have not been able to eliminate it. Ed said that the canister eliminates the jump. Of course it's the dead of winter so developments will be slow at first. Doesn't stop me from doing some bench work tho....

airborne2.4

Great news about the canisters! not so good news about the dead of winter. I watched the report this morning about what's happening in your neck of the woods. I recently got back from Canada where I experienced -29 degree weather[] It sure feels good to be back at home in The Bahamas

MTK

The blizzard? It nearly caught me Friday as I was leaving New Hamphshire to drive back to Jersey. It was at the start of the storm and I am lucky to have gone from our offices just before the storm got bad. They got about 1 meter of snow there; we in Jersey got about 1/3 that much.Driving south on 95was treacherous but I managed. I can't imagine it getting worse and driving in it but judging from the news on TV, many people were not as lucky. Many many cars stranded on the highways.

Anyway, here's snap of the cans along with a 55G pipe for size perspective

MTK

MTK

One of the guys at my field is flying BPLR's last WC's Axiome which is YS175 powered. Oliver is using the same prop as I am using on the 33GT, 20 x 10.5 PN APC.

I now have a side by side comparison of both powerplants. Other than sound and exhaust smoke, there isn't any difference in performance

cmoulder

Matt, are you running pump gas or 100LL?

MTK

Bob,

I am still using 100LL. Premium autogas produces several 100 more rpm but is totally unnecessary. I never use full throttle for anything and neither are YS drivers/users.

BTW-sound quality slightedge goes to the piped OS while downline braking slight edge goesto the YS.

cmoulder

Detonation on 100LL is much more agreeable!

Looks like OS got the stroke and ports juuuuuuust right in order to be happy in the midrange with a 20x10.5.

The DLE 55 shouldn't break a sweat at all.... Can't wait to see both of them.

MTK

cmoulder

Matt, well I have only heard the det difference on your Temptress with the SAP 180, and I can only imagine how much better it is on the more advanced set-ups you're using now.

MTK

Well, the OS is slated for the new Shinden whenever that model shows up. Bryan Hebert told me it will be here around end of May. Aesthesis worked great with the OS at 11 1/4# but I think the Shinden may be a better plane and should be a pound lighter than Aesthesis is. That will be a super duper combo and with more ground clearance I have the 21x10 I want to try. Should be flying mid June

My Delta/DLE55 will be ready before that. I am painting currenty and hoping to maiden mid May.....

JRgraham

My Feedback: (1)

Matt, Icant wait to see that Shinden with the OScombo! Ihave been wanting a new Shinden really really bad! (Heck Id be happy with the last version!)
Because of your work and reports on the GT33, thats exactly the combo Iwould like to put together as well!

Cant wait to see how this go's, please keep us posted!
And thanks for all your effort, and postings here!

MTK

Definitely will do that. We'll try to make a video of that combo at some point. If you have something to put the 33 in let me suggest that youbreak one in and get it ready.They are very tight and take several gallons (4-5) to fully loosen. I have around 16 gallons through mine, approaching 300 flights, and it is running great. Not a singlemaintenance problem since it was returned from Hobby Services when it was new....

Soft mountsI have....ES pipes are highly recommended and available still. Hatori #2301 headers are also available from Hatori USA. Tower is currently running a special on the 33 and with the Super Saver, I picked another one up for $340. The set-up is basically off the shelf

And you are more than welcome. Heck, that's whatI do...love the designing, innovating and building at least as much as the flying.