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HomeAircraftHelicopterThunder TigerRAPTOR 30 › Diesel Raptor 30...
06-03-2009 07:33 AM  9 years agoPost 1
Steve91T

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Roanoke, VA

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This is my first large heli. I bought it used and it needed a lot of work. I also converted an OS .32 to diesel using the Davis Diesel conversion. So far I've only bench run the engine on a stand swinging an 11x6 prop. I've gone through the heli using http://www.raptortechnique.com
I've gone through the entire heli and have all new electronics. Only thing that didn't go as planned is I have no way to mount my digital tail servo off my TREX 450. So, for now I'm using a cheap servo on the throttle and one of my HS 635 servo's on the tail. I figure it'll work for now. I'm going to take it VERY easy for a while.

Anyway, I'm very excited to see how this diesel conversion works. I have high hopes! Supposed to have more tq, less noise, better fuel economy, and no glow plug! Downside is the exhaust is messy. It's hard to tell in the pic, but I got some heater hose from the auto parts store, and used that to couple together two TREX 450 tail booms to use as a muffler extension. The exhaust now runs out past the tail rotor.

We'll see what happens!
Steve

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06-03-2009 07:39 AM  9 years agoPost 2
duceduc

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Saitama-Ken, Japan

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That is the first I heard of a diesel conversion. Make sure to post video and audio. Very interesting.

Duc S
Do It! Do It!™
AMA:REVOMIX
RCK:24005615-01

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06-03-2009 11:36 AM  9 years agoPost 3
Ben-T-Spindle

rrProfessor

Central Illinois

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I have seen Diesel conversions that work well. The trick is to get the carb and compression set correctly. The main downside if Diesel is that the Ether uses as an igniter in the fuel evaporates quickly so sometimes it’s a problem to keep the fuel fresh in hot weather.

... BTS

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06-03-2009 11:07 PM  9 years agoPost 4
cooperd

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Everett

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I've been flying four different diesel powered planks for three years now. Smallest .09, largest .40. Once you get them set up they aren't much different than glo...assuming you understand the tuning process.

You take your fuel to the field in an ice chest, that eliminates the ether evaporation problem.

This heli sounds like a fun idea for sure. I ought to see if Davis Diesel has a head that would fit an OS 32 or 37 heli engine. Hmm!

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06-04-2009 04:58 AM  9 years agoPost 5
Steve91T

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Roanoke, VA

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Can you just add ether to the fuel if you feel it needs it?

They don't have the OS 37 yet, but it's in the works. I actually bought a 37, but then sold it when I decided to go diesel. I bought a used 32 and got the kit for it. They claim it'll have the power of AT LEAST a 37, probably more like a 39 or 40. We'll see. I just got home from a trip and have tomorrow morning to fiddle with it. Sucks that this is my first fuel heli. So, I have a pretty large learning curve. Also my cheap Hobico tach quit working, so I'll just have to guess as to what the RPM is.

I'll post pics and videos tomorrow.

Steve

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06-04-2009 06:21 AM  9 years agoPost 6
cooperd

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Everett

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Yes you can add some extra ether. I will often give a squirt into the can at the start of the day to replenish what has vaprorized away. The original diesel receipe is something like 33% ether, 33% kerosene, 33% lubricating oil like castor oil. A very small percentage of an oxidizer, the name of which I can't remember is also added.

The BEST ether to use is John Deere in the pressurized can. The reason is that their package has the highest percentage of ether. The other auto store brands have less actual ether and that is detrimental to our needs.

When tuning a diesel you are working with two variables. Compression and fuel quantity(needle valve). The trick is to get the engine to run well and produce good power on as little compression as you can get away with. If you raise compression, you must reduce fuel. More compression means less space for fuel...it doesn't compress. As you reduce compression you can add more fuel. The exhaust oil and residue will usually look med to dark brownish if things are correct. If the oil is black you are over compressing.

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06-04-2009 11:34 AM  9 years agoPost 7
chuck4040

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Kirkville, NY Syracuse Thunderbirds

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What is the benefit of converting to diesel in a RC helicopter?

Invertix

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06-04-2009 01:07 PM  9 years agoPost 8
Steve91T

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Roanoke, VA

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Chuck, see my first post, 2nd paragraph.

cooperd, when I was running my engine on the stand, I'd start it up and let it idle for about 30 seconds or so, then I'd start feeding in the power. It would usually run very rough until it generated some heat. Once it smoothed out, I'd leave it at full power and play with the compression. I'd go in slowly, engine RPM would increase. I'd find the point at which it would stop increasing. I'd leave it there, then play with the mixture. From what you said, I was doing it backwards. I need to maybe start with 1 1/2 turns out on compression, and add fuel, then add compression?

You have any video's of your larger plane flying?

Gotta take the dog into the vet this morning. When I get back I'm going to mess with the heli, if the rain holds out.

Steve

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06-04-2009 01:33 PM  9 years agoPost 9
chuck4040

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Kirkville, NY Syracuse Thunderbirds

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Sorry Steve - must be my old eyes - missed that part. At first glance it seemed to be a lot of effort for little gain. Please keep us posted on your progress and thoughts.

Chuck

Invertix

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06-04-2009 01:37 PM  9 years agoPost 10
Ben-T-Spindle

rrProfessor

Central Illinois

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What is the benefit of converting to diesel in a RC helicopter?
Diesel have more torque so they won’t bog down as much.

Fuel costs a lot less.

You get longer flight time.

The disadvantages are tuning and having to deal with a new type of fuel. Some engines don’t idle as well but that’s mainly the carburetor design. I use to fly Diesel in planks until I went to electric. Once you learn how to adjust it they are better than glow for some applications.

... BTS

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06-04-2009 02:03 PM  9 years agoPost 11
chuck4040

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Kirkville, NY Syracuse Thunderbirds

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Ok that makes sense - the same reasons I fly a gasser -but in a smaller package...

Invertix

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06-04-2009 05:53 PM  9 years agoPost 12
Steve91T

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Roanoke, VA

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Here it is!!!!
http://www.youtube.com/watch?v=FoeCVfqSp7s

http://www.youtube.com/watch?v=htYWToUAeRA

After the video, I gave it just a little more compression and it sounded like it was revving twice as high. Right now I'm hovering at 3/4 stick. I think I'm going to change it to about 1/2 stick or so. This was my first time flying a fuel heli. I've only flown a TREX 450, and that was at the end of last year, so I was a bit nervous.

Anyway, I've got some work to do, but I'll figure it out. So far I'm a fan of the diesel. One thing I have to do is get a slightly smaller diameter heater hose, as it leaks at the muffler, and where it attaches to the TREX 450 tail boom/exhaust pipe that runs out past the tail rotor. Another thing to note is the smoke is mostly steam.

I've got to get a new tach. Once I do that I'll be able to get a better idea of what the RPM is. I have no idea what a nitro 30 running an OS 32 is supposed to be like, but seems like it'll have enough power. Especially once I get the tuning correct. I'll have time to mess with it tomorrow.

Coopered, what do you think? It was surging slightly. Think it needed more compression?

Steve

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06-04-2009 06:00 PM  9 years agoPost 13
trunkmunki

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Bangor

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I'm sure you can tune the surging out. I have to say that looks like a great dog you have there. Mine would be trying to eat the thing out of the air!

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06-04-2009 06:46 PM  9 years agoPost 14
BJames111

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San Diego, California

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sounded like it was revving a little high. With the plastic rotorhead, it's not really safe to go over 1850rpm or so. If you get a metal head block, you can go up over 2000 and as long as you keep using carbon blades you'll be good.

I'm intrested to see how this pans out.

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06-04-2009 10:45 PM  9 years agoPost 15
T-Rex-Flyer

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Panama City, Fl

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What does it cost to mix a gallon of your own fuel, and what safety precaution do you need to take?

If the wings are traveling faster than the fuselage, it's probably a helicopter.

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06-05-2009 01:31 AM  9 years agoPost 16
cooperd

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Everett

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Now that is really KOOL! I love it! From the U tube sound it is difficult to hear surging, but the characteristic sound the diesel makes when throttle is closed is there as the RPM backs down.

Quite often when you increase the compression just slightly the engine will suddenly hit it's stride and you will know you are there. From you comment in previous post it sounds like that is what it did! At that point you may be able lean a bit, or if that makes things worse go a little richer.

One thing to realize with the diesel engine is that is produces much more torque than the glo. For example, I have an OS 40 with a diesel head on it that is swinging a 12 x 6 or so prop! Most OS 40's on glo will do a 10 x 8 or maybe an 11 x 5. I've even had a 13" on it once.

So this means you can use that torque to spin the head at a lower RPM with more throttle(power) against that pitch than you could do with a glo engine. Although too low a head speed affects quality of flight sometimes, like the heli wobbles in flight. Diesels are very tolerant of lean operations....they simply quit when too lean! So don't worry too much about that.

With the extra torque the diesel has, you could try the Raptor 50 gear set and see how it handles that...staying with the 500 mm blades.

You are really on to something here! My diesel buddy here is an 82 year old retired Dr and he really perked up when I mentioned your project. I have a 32 engine and a 30 Raptor. But it's my wife's she might object to the messy diesel conversion at the moment.

Making your own fuel is doable, but Davis Diesel Fuel is great stuff, why bother?

Keep up the good work! javascript:smilie(''

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06-05-2009 01:38 AM  9 years agoPost 17
cooperd

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Everett

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Ah, I found an article on making Diesel Fuel. Amyl Nitrate is the mystery ingredient that helps it all work

http://www3.telus.net/dieselcombat/diesel_fuel.htm

It helps to understand the ignition process with these engines. First of all the compression ratio is not nearly high enough to ignite kerosene by heat of compression. It IS high enough to ignite ether, which in turn, with the help of the Amyl Nitrate ignites the kerosene. Probably very little of the lube oil is consumed by the ignition, it just flows out the exhaust creating a stinky, but charming mess!

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06-05-2009 02:09 AM  9 years agoPost 18
duff

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Calgary, Alberta, Canada

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I am very interested in this as well, maybe you can answer a few of my questions?

1)What type of fuel economy does this mod have compaired to nitro? Flying time?

2)What is the cost of the premade Diesel?

3)Are there any mods for the OS50 Hyper?

Thanks

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06-05-2009 02:13 AM  9 years agoPost 19
duff

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Calgary, Alberta, Canada

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Furthermore do you think there would be enough tourqe to use the OS32 on the raptor 50 titan swinging 620s

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06-05-2009 04:56 AM  9 years agoPost 20
Steve91T

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Roanoke, VA

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Duff, I've only run two tanks through it and it was just hovering, but from what I've read, they do get better fuel economy. Can't remember how much better off hand. http://www.davisdiesel.com will have the answer, along with how much their fuel is and a full list of what engines they have heads for. As for the tq, I'm not sure. Right now I'm swinging 550's. I'm sure it would have enough tq, but not sure how good it would do. I wonder if it'd be better to swinger a longer blade, or change the gearing.

Cooperd, that's crazy your 40 swings a 12x6 prop! My OS 46 is swinging only an 11x6. I'm really looking forward to getting a decent tach and setting the head speed to what it should be and messing with my throttle/pitch curves. The engine seems happiest when it's under a load.

This is a fun project! It's really cool that it's so different. Not too many diesel heli's out there.

Hopefully it doesn't rain all day tomorrow. I'd like to do more testing. I'll try to get more video also.

Steve

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