Rotary Engines

[Catfish]

Hello,
just read this over at the aerodrome forum, item is an Omega rotary engine:

" ...Koz,
Your panel looks wonderful but don't forget to use an fuelregulator if you don't the engine will 'explode' after blipping because of the rotation the fuel keeps being sucked in to the cylinders. ..."

Is this so ? So the second in which you "blip" the engine, there is also a complete mixture cut-off ?

Full thread is here:
http://www.theaerodrome.com/forum/aircraft/39333-gnome-omega-overhaul-2.html

Greetings,
Catfish

 

[Baywing]

No, during the blip the air/fuel mixture continues thru the engine and because the ignition (spark) is turned off, raw fuel accumulates on the outside of the engine, on the firewall, on the cowling, etc. That is one of the dangers of blipping, and if it builds up too much, when you add spark again, you risk setting the plane on fire. In the old days before electronic ignitions on cars you could run the rpms up, shut off the igntion switch, wait a few seconds and while the engine was still turning, turn the key back to "on". At that point, raw fuel/air had been dumped in the exhaust system and it would then ignite with a big bang out the tail pipe (if you were lucky, if you weren't you blew your exhaust system off!).
The engine would not explode, per se, with the exception of the early Gnomes running a perfect air/fuel mix in the crankcase where they did occasionally blow the front cover off. LeRhone was an improvement as the mix in the crankcase was so rich it wouldn't burn and was leaned out in the cylinder by hanging the exhaust valve open for part of the intake stroke.

 

[Hylander_1314]

Hylander,

Believe it or not, that was the same problem that plagued the Harley engines for years. The rear cylinder would overheat immediately in traffic, or at low speeds due to lack of cooling air. Seeing it was blocked by the front cylinder and covered by the tank, it suffered.

The Evo engine slightly cured that with some ducting using rubber and a slight shift in the cylinder placement.

Hence why Jap bikes last longer... but aren't as nice looking/clean.

OvS

Aaaaaaaaaccckkkk uuuuuuuuuuggggghhhhhhh!!!!!!!!!!! No rice burners here man!

I ended up doing what CJ said with my '68 Electra Glide Chopper. I also stripped every bit of un-needed frills from around the tank and engine too, and a co-worker in the shop had a machine shop in his back garage, I used it to true up all the main parts of the engine to 10k on the mic. But it also required modified gasketing too due the fine tolerances I machined evrything to. Mine was the only hog that didn't need to be parked over a sawdust pile on the lot. But I also avoided taking it into Philly too if I didn't need to. I stuck with the more rural areas as you can cruise nicely through the backwoods of PA, Delaware, and Maryland.

The real nice part of taking the time to machine everything was it really cut down on the vibration, and kept everything balanced better.

 

[ovs]

The real nice part of taking the time to machine everything was it really cut down on the vibration, and kept everything balanced better.

Yes... HD finally got that right with the last gen Evo's and now the new 88's. BALANCED parts. I don't think the Softails even shake as much anymore out of the factory. The last Softail I rode in Fla I rode from Orlando where I rented it, to Daytona to Jacksonville... then Gainsville back to Orlando... I couldn't feel anything in my hands for hours after that. It was a blast though.

I made a mistake on that engine I was talking about... it was an early model Virago... sorry. I worked on a friend's Virago in college (amoungst all the other bikes I had parked in front of my door). My bad... it was a rip-off of a HD motor, in the sense of it being 2 larger cylinders. But it had ducting and the rear cylinder was slightly off-set for cooling.

No, the HD motors have none-of that. I only rode rice-burners because they were cheap. I couldn't afford an HD... even now, they're a strech, but I will someday. Either a RoadKing, or a Softail Custom. They ditched the Wide-Glide for some reason... they aren't making it anymore.

Thankfully Harley's prodcution quality has soared compared to the early 80's crap that they used to have. Even some of the early Evo's suffered from exactly what you mentioned, bad machining. But things are much better now.

I'm still waiting for the '2 for 1' sign in my local dealer so I can convince the wife she can have her own. But riding here in Long Island is a deathwish anyway, so I'm in no rush.

OvS

 

[ovs]

I have ridden this bike in 100F degrees ambient air, plus sitting at 3 minute long stop lights, with no over heating issues ever. I will say the only thing that did over heat was me!

You're lucky then. 4 of the guys I rode with in Florida had HD's and it was panic time for them sitting it traffic. You could hear their motors getting louder and running sick. At the time I had a modified CB750, which had no issues.

Tomoka State Park... now that was a run...

OvS

 

[Cameljockey]

When I was in the Navy in '80 I had a '72 CB750 Super Sport that I bought from a fellow sailor who was shipping out. They're runners right out of the box but I did a little work to it. I bought an 836cc kit (the SOHC 750 was actually 736cc) which consisted of new jugs, pistons, rings, 4-35mm Mikuni smoothbore carbs, and a four to one header. I had to get the head machined for the larger bore, but when I got it put together it was really a screamer. I laced a 16" wheel onto the stock hub so I could run a fatter tire. That narrow stock 18" tire just burned when you would get on it. It would give those 900 and 1000cc Kawasakis a run for their money! I love bikes but every morning when I get up my bones remind me of my Motocross days.

CJ

 

[Hylander_1314]

One thing I did have to do, and I forgot about it since it's been 20+ years since I had a scooter, is you do have to keep an eye on the base of the carb on the older Harleys. I went through 3 of them until I figured out that from heating up and cooling the darn base of the thing would warp over time, and I ended up solving it by machining my own from stainless stock. The flanges the nuts and washers locked down were too thin. I spent about a week measuring and drilling cutting and milling everything, for a couple hours every night, but that was the only way I got the thing to stop doing that. Had to put longer studs in to compensate for the thicker flanges, but never had another problem like that again. Not sure if it was a problem on the later bikes, and I'm sure they've been using direct injection for some time now.

Funny thing is I did something similar to the old Stromberg 2 barrell carb I had on my 65 Dodge Coronet 440. The future Mrs at the time and I at the time had driven down Vegas for a few days as her Dad was there for wholesale jewelry shows, so we decided to drive down, as I do not like jets. If I can't see the prop sinnin', I do not get aboard the thing. But we ended up driving down there, and I noticed the engine wasn't tickin' nprmally like it had been. And I thought maybe I got some bad plugs or tune up parts in the distributor, and nursed the old girl home. Checked the plugs, wires, points, and even pulled the distributor to check the cam gear, and bushing seat, and vacuum advance, and it all checked out, so the next step, was firing it up, and going around the areas for the intake and carb with a can of brakeparts cleaner, and sure enough, on the left rear corner, if you shot some fluid at the base, the idle shot up. The cast iron intake was true where the base was, but the darn carb had warped. At least I knew what to do the next time round.

Cool thing about the trip was getting her diamond engagement ring for a song from one of the importers down there. A full carat blue diamond with 24 carat gold setting for less than a grand. She's kept it for our daughter. So that was cool of her to do.

Anyways, weren't we talkin' about aero engines when we got distracted and not only hijacked the thread, but turned it into a trainwreck?

Man I can't wait 'til spring :fish2:

 

[Fortiesboy]

Thanks everyone for this input it really is fantastic. I am seeing my friend over the weekend and I am going armed with all this. He is going to be very interested!

He servered in the Royal Air Force and clocked hours on the Lightning. Thats the English Electric Lightning not the P38!!

Hello Wildfowler - yes, my golfing mate was a Lightning pilot too. Has flown Spits as well. He's had a go at this simming and reckons it's harder than the real thing -lol
As to the topic, I have been flying the rotary planes - DR1 etc in the sim on two buttons on my HOTAS. I have full throttle or approx half, - or minimum throttle, where it "coughs".
Makes the dogfights interesting!

 

[Wildfowler]

Hello Wildfowler - yes, my golfing mate was a Lightning pilot too. Has flown Spits as well. He's had a go at this simming and reckons it's harder than the real thing -lol
As to the topic, I have been flying the rotary planes - DR1 etc in the sim on two buttons on my HOTAS. I have full throttle or approx half, - or minimum throttle, where it "coughs".
Makes the dogfights interesting!

My friend said much the same about sims. He felt it was the lack of movement that made it harder!

These references to motor cycles are interesting. I have heard it said if you can ride a horse you can learn to fly quite easily and riding a motor cycle also helps.

In fact at my board for a commision in the RAF a rather wizzened old Wing Commander on the panel asked me
"I say, can you ride a horse?"
I stated I could. Low and behold I was commisioned, that was the only question of the entire interview I knew the answer too!!!
Mind you some time later whilst serving as a Pilot Officer I met him at some mess do and he offered me these words of advice
"As an Officer remember, never be afraid to ask your NCO for advice, always make a make a decision, stick by your decision, back up your NCO's and men. Remember this.....and there will always be someone to put in a good word for you at the Court Martial!"

Words to live by!!!