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HomeAircraftHelicopterThunder TigerRAPTOR 30 › Diesel Raptor 30...
06-05-2009 05:37 AM  9 years agoPost 21
cooperd

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Everett

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Yes Steve, I agree. It never occurred to me that it might be possible to convert an existing heli engine to diesel. That makes it an easy to do bolt in conversion. Plus with pitch and throttle curves and possibly the use of other gear sets the possiblities for tuning are numerous.

Clever using the Trex 450 boom for a tailpipe. I do the same thing on a 6' airplane powered by a .40 PAW diesel. The tail boom turned tailpipe conducts all the mess away from the airplane and keeps it nice and clean.

Some model plane engines don't lend themselves to good diesel conversions. Those that use airbleed screws for low end don't seem as tuner friendly as those using actual fuel metering. The Heli carb should do really well in the tuning department.

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06-05-2009 04:59 PM  9 years agoPost 22
Swoop

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Newark, DE USA

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Very cool conversion. I've seen long exhaust extensions choke a nitro motor down to being virtually unrunable. You obviously aren't having those issues, but it does beg the question of how the restricted exhaust may be hindering performance.

Chris
X50, B320, Radix, Spartan
Titan,Kasama,MP5,Radix,JR770
Trex450SE,MavrikkG5,Phoenix35

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06-05-2009 05:11 PM  9 years agoPost 23
Steve91T

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Roanoke, VA

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Diesels can handle some back pressure. But at the same time, I made sure that the 450 tail boom is the proper diameter to have as little restriction as possible.

Steve

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06-05-2009 09:37 PM  9 years agoPost 24
Swoop

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Newark, DE USA

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Cool Steve, just checking that you were aware. Good luck

Chris
X50, B320, Radix, Spartan
Titan,Kasama,MP5,Radix,JR770
Trex450SE,MavrikkG5,Phoenix35

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06-06-2009 01:19 AM  9 years agoPost 25
JuanRodriguez

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The Villages, Florida

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But at the same time, I made sure that the 450 tail boom is the proper diameter to have as little restriction as possible.
Steve,

How did you determine that ?? Roll of the dice ???

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06-06-2009 01:45 AM  9 years agoPost 26
Steve91T

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Roanoke, VA

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Looked at it. Not too hard to see that it was pretty damn close.

If it wasn't, I wouldn't have used it. I was going to use heater hose, but the 450 tail boom is much lighter.

Steve

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06-06-2009 01:47 AM  9 years agoPost 27
JuanRodriguez

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The Villages, Florida

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Oh, Ok....
I thought that maybe you had some kind of scientific formula.....

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06-06-2009 11:51 PM  9 years agoPost 28
cooperd

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Everett

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Yes, diesels are tolerant of back pressure. I run a full length Trex 450 tail boom as an exhaust for my PAWS .40 diesel and it works great! Pipes all the slim away from the plane. I just stuffed the end of the boom into a standard 40 size exhause extension and it provided the elbow and flexibility.

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06-08-2009 03:47 AM  9 years agoPost 29
Steve91T

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Roanoke, VA

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Had the heli out today. I gave the compression another 1/8 adjustment increase. It started right up and obviously ran like crap. I just put it into a high idle till it starts to warm up. Once it got some heat in it, it smoothed right out. Flipped the switch and went into a hover and started the clock. It hovered beautifully and the engine was as smooth as can be. I was punching it a little, did a few piro's, and played with the throttle curve. When I landed, I had very little fuel left. I hovered for just over 23 minutes. This is with the header tank bypassed.

That's fairly decent, right?

Anyway, clean up was a snap. The main blades had just a little oil on the last 1/4 of them and that was it.

I love this thing!

Steve

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06-08-2009 04:13 AM  9 years agoPost 30
spaceman spiff

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Tucson

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Found the Davis website does list a kit for the OS 50. 91 as well...

hmmmm... Looks like a hoot to tinker with.

http://davisdieseldevelopment.com/price_list.html

http://davisdieseldevelopment.com/home.php

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06-08-2009 05:34 AM  9 years agoPost 31
eMeNeX

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Northern Virginia

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This diesel conversion thing is making me want to convert my Hawk Pro with OS 32. What's the starting procedure like? I saw your youtube videos and it looks to be pretty stable. What are the cons to the conversion?

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06-08-2009 12:18 PM  9 years agoPost 32
Steve91T

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Roanoke, VA

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I kinda wish I had flown the heli as glow first, just to compare. To start it, I fill it with fuel, crack the throttle and hit the starter. For the first initial cold start, it'll take a couple of hits with the starter until it fires. When it's cold, it'll romp and surge. I have my pitch and throttle curves set for flat pitch and a linear line for throttle. I then use that to let the heli spool up to a high RPM for about 30 seconds. Then once it gets some heat in it, I flip the switch and will put some negative pitch on the blades to load the engine. Then it really clears up and then you're good to go.

For warm starts, crack the throttle and bump the starter. Fires right up. No glow plugs!

As for right now, I don't know what the cons are. I guess there's a bit of a learning curve on how to tune the engine, but the instructions that come with it are pretty good. Also you can call Mr. Davis himself and he's very helpful. The other thing is you can't just run down to your local hobby shop and get more fuel. You have to order it. I ordered 2 gallons at one time to save on fuel.

I'm going to pull the tail apart this morning to secure that stupid pin that causes so much trouble, then I'm taking it to the flying field. I'll bring my camera and try to get some video.

I wish I could find a video of someone with a Raptor 30 w/ OS 32 in a hover, then punching it straight up. I want to see the power difference of a glow version. They say that the diesel 32 should have as much power as at least the 37, maybe a little more,

Steve

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06-08-2009 03:41 PM  9 years agoPost 33
Ben-T-Spindle

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Central Illinois

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What does it cost for fuel?

... BTS

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06-09-2009 08:40 PM  9 years agoPost 34
Steve91T

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Roanoke, VA

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Ben, I don't recall what fuel costs. I ordered it back in Feb along with everything else I needed. You can send them an e-mail, they are usually very quick to respond.

Cooperd, I'm having problems with the engine. It seems that once hot, I've got a fuel delivery problem. I've got brand new diesel friendly fuel lines, along with a new clunk. I'm just running off the main tank, not using the header tank.

This is causing a hot starting problem To the point where I almost can't even get it to start. Once I do, it's surging VERY bad.

Another thing is I can't get the idle low enough to keep it running without the clutch engaged.

I have a feeling everything is related to the fuel issue.

Any thoughts on this?

Steve

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06-09-2009 08:51 PM  9 years agoPost 35
dashpilot

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Abu Dhabi, UAE

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looks good amigo! When are you going to bring it up here?

"what comes up must come down"....softly of course

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06-10-2009 03:52 AM  9 years agoPost 36
Steve91T

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Roanoke, VA

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When I get this bird flying right! I'll hook up the header tank tomorrow and see how t goes.

Steve

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06-10-2009 05:01 AM  9 years agoPost 37
cooperd

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Everett

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Steve, my experience with idle and the diesel is that the higher the compression setting the poorer it will idle. You might try coming off the compression a bit.

Your observation is correct...when the engine is cold it runs really rough and knocks and rattles. It has to warm up a bit before it somes out. That is pretty much normal ops.

Hot starting problem, not sure from your description. But a trick we use on our diesels is to clamp off the fuel as soon as you shut down. The ether vaporizes in the tank and pushes fuel into the engine making it hard to start(flooding) as well as making it easy to bend a connecting rod if too much fuel is in the head to compress.

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06-10-2009 01:11 PM  9 years agoPost 38
Steve91T

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Roanoke, VA

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That's interesting about ether vaporizing. I doubt that's my problem, but it could be. When I try to start the engine hot, I can see a ton of air in the fuel line. And if I do get it started, it runs VERY poorly because of the air. I'm going to hook up the header tank and see if that helps.

As far as being over compressed. Remember by video's I posted? You could hear the engine surging. Well I went about 1/8 of a turn in on the compression and it ran 10 times better. Maybe I just needed to leave the compression where it was and add more fuel. I'll give that a try.

re-seat the carb
hook up the header tank
less compression, more fuel

I'll mess with it tomorrow and see what happens.

Steve

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06-10-2009 03:01 PM  9 years agoPost 39
dashpilot

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Abu Dhabi, UAE

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I'm sure you'll figure it out... patience's grasshopper

"what comes up must come down"....softly of course

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06-10-2009 03:44 PM  9 years agoPost 40
Ben-T-Spindle

rrProfessor

Central Illinois

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You need to keep the fuel cold in an ice chest and fill it up just before you start it. If you land with a lot of fuel in the tank you should probably suck it out and put it in the ice.

In the summer that’s what I had to do when I way flying Diesel airplanes and it worked great. Another trick that I worked was to transfer gallon cans to quart cans the first time you open the gallon can. That way the evaporation was kept to a minimum and the fuel stayed fresher longer.

Be sure and use the correct container, as the furl will dissolve most plastic bottles over time. For that reason don’t leave any furl in the helicopter tank after you finished flying. The fuel lines may also mot last as long so keep an eye on them

... BTS

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