bklambdin

Yeah Dave H,it you could look up the rest of the fuel mix. If the Davis mix is 12% oil, is it castor or synthetic? I have some KL-200 synthetic for mixing with methanol and it will mix with kero as well. Where and how do you get the ether? And the Amsoil Cetane booster?
I've read John Deere starting fluid and putting it in the freezer then poking a hole and pouring it out, I would rather buy it un-compressed if I knew where.

The reason I thought about going to a larger pinion was just what you said, but now after I got the pinion in, it was for the Raptor 60\90 and not the 30\50.

With the gear ratio I'm running, it puts the engine turning at a little over 15.5K, which is where the engine makes the max power and works perfectly for glow fuel. I think the specs for the os 50 hyper is 2k 18K and max power at 15.5K. This seems to over heat the back side of the engine, But I'm flying longer, per tank, I don't have to land and refuel. I think if I were to fly the same amount of time, land and let it set to cool off it would not get so hot. Just don't do 15 - 20 minute flights. Mr.Davis wrote me and said 15K was just a crazy speed for the engine running diesel, but I hve no choice since the larger pinion is not availible or I can't find one.

bklambdin

And what about the tuned pipe vs the stock muffler?
Mr.Davis reccomended using the stock muffler.

Would the tuned pipe let more air flow and flow more freely and thus reduce the heat via pumping more oil through the engine? But of course that would be more fuel as well which could make it hotter. Or with the more air flowing may give more power and thus allowing the engine to run easier and not put as much a strain on it.
But still the engine will be turning a RPM of 15.5K because the govenror must hold the head speed at 1850 RPM's for sport\3D flying.
Unlike planes, I can't just put on a bigger prop and the engine must maintain a constant RPM because of the tail rotor and head. Just a fluctuation of 100 RPM's on the rotor speed will cause the tail to wiggle or wag which just cannot happen on heli's.

This is an exciting experiment and so far I have enjoyed the tinkering and results.

gerryndennis

Brian,

Bob's ABC and racing blend is 32% ether, 12% oil, 2% booster and balance kerosene. Interestingly enough this blend has the ratio of ether to kero almost identical to the other mix mentioned, just a reduced amount of oil. I haven't tried it, but diesels can tolerate lower oil content, I don't know if I would try it in a helo though.

He says you can use up to half the oil synthetic with the rest castor. So your Klotz should be fine mixed with castor

He can provide booster (it says here) either hexapropyl or isopropyl nitrate. I think a lot of people in the states use Amsoil cetane booster for cars quite successfully. Where to get it? Sorry cant help you there but it must be around.

I understand that most guys in the states are tapping John Deere starter fluid cans for ether.

I guess Bob is saying that his conversions make their best power at a slightly lower RPM than the same engine on glow but this will vary from engine to engine, like I say mine was about the same RPM. I'm sure the RPM you are stuck with will be fine. There's plenty of racing diesels turning higher than that.

Bob has special tuning instructions for using a tuned pipe, they may be for a propellor engine, but maybe you could ask for a copy of those.

You seem to enjoy tinkering so try the pipe, also try using 100% throttle.

As for the overheating, well I don't really know, but you want to be very sure that you aren't over compressed. Black oil and a hot engine may be symptoms of over compression. We normally tune diesels for minimum fuel and minimum compression. Lean the needle until the engine sounds harsh then richen slightly, increase compression until it just stops burping. The mixture and compression interact so a richer needle needs lower compression. I don't know how this translates to helicopters or how you go about setting an engine up for high RPM partial throttle running. That's your area of expertise.

Sometimes you have to set a higher compression for starting and then back off for running. Have you tried backing off the compression after warm up? With an electric starter you may be fine starting at a lower running setting as long as you let the engine warm for a while before flying.

Hope this helps.

Dave H

qazimoto

My Feedback: (1)

Some racing diesels for control line do use 12% oil and less. However they don't run flat out for 15-20 minutes. Maybe 6 to 7 minutes with say four brief stops and restarts.

Also the cowling tends to be extremely close and designed to force the internal slipstream through the engine cooling fins to maximize cooling.

I wonder if a little extra oil added to the Davis mix might help lower the head temperature.

Also it might be timely to pull the engine apart and check how the rod ends are coping.

Interesting topic, especially the notion of using a quarter pipe on a diesel.

I've heard people talking about doing it but have never heard of anyone succeeding yet. Has someone done it?

So many questions.

Ray.

bklambdin

Thanks guys.

I'll post the results of full throttle and a tuned pipe along with a higher oil content.

I'll do it one at a time to observe the results of each and post each experiment when I do.


Brian

Recycled Flyer

Brian, any chance of increasing the efficiency of the cooling fan/impeller?

Or using a shroud to direct that airflow to the cylinder head?

Still can't but help think that you simply need more fins on that head though since with a rotary wing heli the airspeed could well be zero but the engine speed (as you say) 15 000rpm - that's a lot of heat with no external air flow to assist in its removal.

The tuned pipe, from what I have heard (and it makes sense) you can make use of them on a model diesel but the compression ratio will be tied to the rpm. In other words it may well work at 15 000rpm but below that rpm it 'should' be under compressed.

(I read about a bloke years ago who reported using a straight length of pipe from the back of an Oliver Major diesel and fluked a reliable 300 rpm extra for his troubles.)

bklambdin

Yes I'm investigating the new aluminum fan upgrades and I'm trying to figure a way to direct more air across the engine.
I flew it 5 times today and limited the flights to 7 minutes per, same as you get on nitro, the engine didn't hardly get as hot but still the back of the engine reached 145 150 and the head was in the 125 degree range. Head is cooler but the carb and back of the engine is still hotter. The air flow is designed for the head, that is where the heat is at for nitro. I'll figure out how to open it up for more air and redirect the air.

One if the guys watching it fly today is going to convert his to a diesel. I got more power, 3 times the fuel milage, and if I can brew my own fuel it's a no brainer, all 3 of my heli's will be diesel. And like he said, the smell aint that bad, no worse than nitro really.

Thanks
Brian

fiery

My Feedback: (2)

The smell is addictive Brian.

gerryndennis

Fiery is right, diesels smell beaughtiful, and have the added advantage of making your clothes and car smell nice for weeks as well.

150F? that's about 65.5 C. That doesn't sound too hot to me, but I have no idea what a normal temperature would be. If they are running correctly then the temp is irrelevant to me, but it may be different in helicopters?

I wonder if a diesel on a pipe may actually be easier to deal with in a constant RPM set up like a helicopter. You won't have the engine coming on and off the pipe with the attendant changes in compression.

I'm looking forward to hearing how it goes if you decide to try it. Once again be carefully not to end up over compressed though.

Have you asked Bob Davis for his tuned pipe instructions?

Dave H

bklambdin

I've sent him a email asking or the tuned pipe instructions.
The thing runs perfect, just a minute of warm up time before it will spool up, then no problems at all more power, more gas milage, most of the brown castor I believe is what DD runs is blown down and out past the heli so its no more of a mess than nitro.

I watched a guy yesterday use almost a full tank of nitro getting his main rotors set. When the heli leaves the ground, if you can see both blades its a bad thing, so you land adjust the linkages on the blades, take off again and watch, land make another adjustment blah blah.
I was laughing saying it took 7 dollars to adjust the blade tracking.

gerryndennis

Ah rotor tracking, been there done that with full size.

Start up, warm up, takeoff checks, pull in to the hover, take viberex reading, strobe the blades for tracking, land two minute cool down, shut down, a couple of minutes for the rotor to stop, snip the lock wire, adjust the linkages and or add weight, re lock wire the adjustments, duplicate inspection, start up etc. Could easily take all day and burn a bit more than $7 worth of jet fuel.

Sounds like you've got the diesel helicopter pretty well sorted, well done. Now just the you tube video to upload.

Dave H

bklambdin

Yeah I will take a video and get it uploaded for all to see. With the rising cost of nitro fuel and the low cost of making your own diesel a lot more may convert to diesel.

Brian