Notice how much better this engine runs right near the end of the tank. I am curious if my tank height was a bit too high. The center line was right in line with the HSN, but when the tank is full perhaps there is too much fuel pressure. I have lowered the tank 1/4" to see if this makes a difference. I will also be doing static thrust readings with this 13x4 prop.
Your prop size and weight has a flywheel effect on the engine. I turned a copper flywheel and mounted it to the propshaft behind the prop, smoothed out the idle problem.
Wow, this brings me back to my youth. I tried diesel by modifying an ST60, about 35 years ago! Had to machine a new head by myself, and tapped a compression plate, in similar fashion to yours. Using the stock carb, I was able to achieve a really strong high speed setting. But low speed was a big challenge. I had to change carbs, but cannot recall which carb brand did the trick. Diesel requires more air than glow, so the needles must be super sensitive. I recall I needed to find a carb with needles having very long taper. High speed was achieved by adjusting compression, but I wondered always if more air flow from a larger bore carb would achieve greater rpm. For the idle, a prop that produced a higher load in turn produced a better idle. Your comment about a larger prop for flywheel effect is interesting, but doubtful; I suspect the effect has more to do with loading. True, I could run much larger props, but the prop pitch had more effects than the size, per se. I found the engine ran consistently high and low, if I used the same prop consistently to tune and run the engine: changes in props required retuning. And, without doubts, diesel is a challenge in all respects. Everything can affect the engine performance. A slight change in fuel, retune. A change in prop, retune. A change in weather, hot/cold, wet/dry, retune. Then comes the odour: kerosene with ether is very "aromatic", and is very difficult to remove from skin and clothes. Then comes the exhaust residue: it will be black, smelly, oily, sticky, and nigh impossible to clean. I flew an ugly stick, with an aluminium tube the entire length of the fuse to exit at the rudder, and still had residue on the plane. Mind, back then we used castor, so a problem: I expect the synthetics of today would burn very much cleaner. When I could no longer purchase ether, I did try to go minus ether, but engine starts were nigh impossible. The engine needed the high volatility of ether [as no RC engine can produce the very high compressions needed for non-ether fuels], and nothing else substituted. So ended my foray into this fuel. I may try again though.
one thing I heard about diesels, not sure it true or not, is that they tolerate very long exhaust extensions that glow motor would not. If true, that will come in handy if you mount this on a plane in order to minimize mess.
ya got er dialed in quick. If you have a .20 FP carb, you will get an absolutely superb run. Diesels will thrive on a smaller intake and get better duration.
Did you readjust the high speed needle after you opened it 1/2 turn before this run? Where did the air bleed screw end up? What is the cost of the fuel? Good job figuring it out.
I just reviewed the unedited video again. It looks like I leaned the HSN about 5 clicks and I made no changes to the airbleed screw. These 1 quart cans of Davis Diesel fuel are $12 each at Tower Hobbies.
So whatcha gonna put this on? What would be the advantage of running a diesel engine? Is the fuel cheaper? I know you mentioned before that you can't just go to the pump and run pump gas in it.
I have no plans to put this on an airplane. The advantages are. Cut and paste because I already answered this in the comments section of Part 3. I guess the main advantages of diesel are as follows: 1. No glow plugs to burn out and replace. 2. No ignitor battery to charge. 3. Ability to swing a larger prop than you would with glow and thus generate more thrust. 4. Better fuel economy also.
Ok, sorry I didn't see those in the other comments. How much is the fuel? And I"m assuming the only way to stop the engine is by either sticking your fingers in the prop (not recommended) or just letting it run out of gas right?
Gotcha. I was thinking that after I replied. Usually I have my radio set up to have it idle when I bring the throttle all the way down then use the throttle trim to close off the air supply and shut it down. Could probably do the same here. And sounds like fuel is about the same cost as nitro fuel.
DO you live in an area where ether is easy to get? Do you mix your own fuel? Very hard to get ether here in the US, so for me to make the fuel would be a pain in the ass.
I live in Canada, I use john deere starting fluid. It's 80% ether. My mix is 30 % ether 36% kerosene and 33% castor oil. I would rather use Davis Diesel but no hobby shop her in Canada will order it in.
Here in France ether is hard to find in good quantity, too. And there's no supplier for Diesel Fuel... Your video is very instructive and you have achieving a very good setting with good idle and very nice power ! I don't think the .40 FP would run a 13x4 at 9600 RPM in glow mode !
I've just watched some videos from the UK of a PAW 0.49 and a PAW 60 (Brian Cox, check them out). They start first time and idle is just superlow and stable and transitions are near-instant. Diesels got a bad reputation in the US for some reason. I'm not so fond of the burned fuel smells but modern diesels are amazing.
The old smoker. Oh yeah... Very nice job David, you engine doctor you...
Notice how much better this engine runs right near the end of the tank. I am curious if my tank height was a bit too high. The center line was right in line with the HSN, but when the tank is full perhaps there is too much fuel pressure. I have lowered the tank 1/4" to see if this makes a difference. I will also be doing static thrust readings with this 13x4 prop.
So happy you stuck with it. Great job as always. I really learned a lot from this series.
Your prop size and weight has a flywheel effect on the engine. I turned a copper flywheel and mounted it to the propshaft behind the prop, smoothed out the idle problem.
Wow, this brings me back to my youth. I tried diesel by modifying an ST60, about 35 years ago! Had to machine a new head by myself, and tapped a compression plate, in similar fashion to yours. Using the stock carb, I was able to achieve a really strong high speed setting. But low speed was a big challenge. I had to change carbs, but cannot recall which carb brand did the trick. Diesel requires more air than glow, so the needles must be super sensitive. I recall I needed to find a carb with needles having very long taper. High speed was achieved by adjusting compression, but I wondered always if more air flow from a larger bore carb would achieve greater rpm. For the idle, a prop that produced a higher load in turn produced a better idle. Your comment about a larger prop for flywheel effect is interesting, but doubtful; I suspect the effect has more to do with loading. True, I could run much larger props, but the prop pitch had more effects than the size, per se. I found the engine ran consistently high and low, if I used the same prop consistently to tune and run the engine: changes in props required retuning. And, without doubts, diesel is a challenge in all respects. Everything can affect the engine performance. A slight change in fuel, retune. A change in prop, retune. A change in weather, hot/cold, wet/dry, retune. Then comes the odour: kerosene with ether is very "aromatic", and is very difficult to remove from skin and clothes. Then comes the exhaust residue: it will be black, smelly, oily, sticky, and nigh impossible to clean. I flew an ugly stick, with an aluminium tube the entire length of the fuse to exit at the rudder, and still had residue on the plane. Mind, back then we used castor, so a problem: I expect the synthetics of today would burn very much cleaner. When I could no longer purchase ether, I did try to go minus ether, but engine starts were nigh impossible. The engine needed the high volatility of ether [as no RC engine can produce the very high compressions needed for non-ether fuels], and nothing else substituted. So ended my foray into this fuel. I may try again though.
one thing I heard about diesels, not sure it true or not, is that they tolerate very long exhaust extensions that glow motor would not. If true, that will come in handy if you mount this on a plane in order to minimize mess.
The Transition is really good!! So Surprised
Another great Video, I have 2 of these engines sitting around doing nothing, I might try a conversion on one some day👍
That engine runs very well with that propeller now. It could be used in an airplane. I am impressed.
Yes I have it running quite well I think. Big relief too after yesterday's run. Did you see the temp readings from yesterday?
Hey David thanks on all your great help on timing fs and how to repair them brother you are the man Sir........
Will it run on pump diesel?.....like from a gas station?
ya got er dialed in quick. If you have a .20 FP carb, you will get an absolutely superb run. Diesels will thrive on a smaller intake and get better duration.
Yeah, she is sounding pretty good now.
Did you readjust the high speed needle after you opened it 1/2 turn before this run?
Where did the air bleed screw end up?
What is the cost of the fuel?
Good job figuring it out.
I just reviewed the unedited video again. It looks like I leaned the HSN about 5 clicks and I made no changes to the airbleed screw. These 1 quart cans of Davis Diesel fuel are $12 each at Tower Hobbies.
Awesome. So what was the change that made the idle work? Just messing with the air bleed or did the prop make he difference?
Really unsure for sure.
Perfect run
I had a cheezy grin going too Dave. Are there tuning similarities between glow engines and
diesel as far as idle mixture and the HSN?
No, not at all. It is a totally different animal.
So whatcha gonna put this on? What would be the advantage of running a diesel engine? Is the fuel cheaper? I know you mentioned before that you can't just go to the pump and run pump gas in it.
I have no plans to put this on an airplane. The advantages are. Cut and paste because I already answered this in the comments section of Part 3.
I guess the main advantages of diesel are as follows:
1. No glow plugs to burn out and replace.
2. No ignitor battery to charge.
3. Ability to swing a larger prop than you would with glow and thus generate more thrust.
4. Better fuel economy also.
Ok, sorry I didn't see those in the other comments. How much is the fuel? And I"m assuming the only way to stop the engine is by either sticking your fingers in the prop (not recommended) or just letting it run out of gas right?
No worries.
You stop the engine just like any other engine, remove the source of fuel. The fule I bought was from Davis Diesel and it was $13/quart.
Gotcha. I was thinking that after I replied. Usually I have my radio set up to have it idle when I bring the throttle all the way down then use the throttle trim to close off the air supply and shut it down. Could probably do the same here. And sounds like fuel is about the same cost as nitro fuel.
Can you get some static thrust numbers from it? I'd be VERY curious to see static thrust numbers in relation to RPM.
I'm sorry. I no longer have my static thrust setup.
I have switched to diesels to avoid the cost of plugs and fuel. I have mostly PAW's
DO you live in an area where ether is easy to get? Do you mix your own fuel? Very hard to get ether here in the US, so for me to make the fuel would be a pain in the ass.
I live in Canada, I use john deere starting fluid. It's 80% ether. My mix is 30 % ether 36% kerosene and 33% castor oil. I would rather use Davis Diesel but no hobby shop her in Canada will order it in.
I can order JD starting fluid, but here in the urban area 'there ain't no tractors round'... LOL. And no suppliers of that stuff.
that's the shits. I would think NAPA auto parts or pep boys would have it.
Here in France ether is hard to find in good quantity, too. And there's no supplier for Diesel Fuel... Your video is very instructive and you have achieving a very good setting with good idle and very nice power ! I don't think the .40 FP would run a 13x4 at 9600 RPM in glow mode !
What are you going to put this engine in? I hope you're going to fly it.
ua-cam.com/video/vN-sK7TQav8/v-deo.html
Really Cool!!!
Put it into a tmaxx and put a f450 body on it
It's extremely hard to get those diesel's to idle
I've just watched some videos from the UK of a PAW 0.49 and a PAW 60 (Brian Cox, check them out). They start first time and idle is just superlow and stable and transitions are near-instant. Diesels got a bad reputation in the US for some reason. I'm not so fond of the burned fuel smells but modern diesels are amazing.
i love my diesels i have a few videos on my channel