AndyW

My Feedback: (1)

You're right that substituting a head that takes a stock plug helps throttling a great deal but at the expense of top end. Note that my RC version of the .09 uses the stock plug. I never owned an RC .09 so I don't know how they compare. Maybe we could run ours on specified fuel and prop and compare?

Dan Vincent

Andy,

I have some new Norvel Fuel and a bunch of Cox "Super Power Fuel" #551 that is still unopened. I'll probably use 7'X 4' props or in that range. I think the TD likes a little less pitch.

Have to go to NY for a few days next week and then we'll have seven house guests for a month so it may be some time before I can get to it.

AndyW

My Feedback: (1)

On my post on 1/8A batteries, I gave credit to Kelly McCombs, (RingWinger) for initiating another look at small Nimhs for .010 powered aircraft.

Well, he's done it again.

Kelly has been converted to SMALL by way of the design of a unique DeltaPlank design. Sort of a combination of a plank wing and a delta wing. His co-conspirator in the project built an electric version but Kelly hasn't succumbed to the evil art of electron manipulation for the motivation of flying machines. He's gone and got hisself nearly the perfect small engine,,, the Norvel .074. His dilema was that while he had a starter, it was too big for the little .074. He suggested that maybe somebody makes a spring starter for it. They do, Norvel does. Well, they make/made one for their tank mount/.06 engine. I had a few of these laying around and as the pics show, they're built a tad heavier than the typical Cox starter spring. Maybe Norvel had in mind that they also be used to start the .074?

Well, the only .074 that I had that was flying and accessible was my diesel version. So, I installed it quick and dirty fashion by tucking the holding end under the web on the Hayes mount I'm using. To my immense delight, the engine fired off with just a couple of drops of prime and a quick snap of the spring. Amazing. And, hot starts are one try affairs with no prime required. This was on the bench so the acid test was, and diesel guys like to brag about this, the acid test was to go flying with plane, transmitter and just a small bottle of fuel.

Did that with eight ounces. Put in four flights till it started to rain and I still had fuel left. All starts were instant affairs and behaved no differently than if I had used an electric starter. My quick attach affair worked but at the end of the day, I found some score marks on the back of the blades. At full bore the spring assembly rattles forward. The fixed end of the starter can easily be bent into a loop and secured with a screw to one of the mounting lugs. That'll be done tomorrow and no longer will I be grounded because my field box battery kaffed on me.

If it starts so easily as diesel, it sure as #*&@ is going to start as glow.

The additional plus in this is that by using a spring starter, that poor, skinny little rod will get a break,,, well,,, you know what I mean. No more bent rods, 'specially as a diesel.

Amazing little Norvel .074. The little engine that could,, and then some.

AndyW

My Feedback: (1)

OK Dan,

Let me know nitro % and brand of prop and we'll give it a go later.

Andy

Japanman

Hi Andy,
I always enjoy reading about what you're doing. Someone very kindly sent me a (davis)diesel head + warning! to play with, and darned if i have not done a thing with it yet. It will need a bit of modification to be a runner, but I imagine from what I hear that Coxs (049's)really need a new crankshaft otherwise they break- especially the reedys. Now I have a way to re-furbish cox 049 pistons at some stage I`ll give it a go. I WILL have to find starter fluid here which will be a challenge.
I think I offered this a while ago but maybe you did not see it- if you have any old 049 pistons/cylinders around you can send them to me and I`ll bump the piston and make it a go-er again. It may be good for diesels in that i can make it tight enough to bind at tdc. This offer is open to anyone who has cox stuff by the way.

J.M

Dan Vincent

JM,

Bob Davis did have heavy duty replacement crankshafts for the Cox reed engines because the stockers would snap with a diesel head. I never bought one but others have highly recommended them if you want to have trouble-free engines.

The TD shaft seems to hold up well but I don't know if the Medallion shaft is as strong. It has a smaller intake window so it should be stronger.

I have the Davis and RJL diesel heads for Cox .09's so I have it on my agenda to compare TD and Medallion .09's for performance. I'm thinking the Medallion might be a good choice for diesel power because diesels don't need dual bypass ports to get enough mixture into the jug.

Tatone made a clamshell style exhaust collector for the Medallion that would muffle and provide a way to keep the fuel off the model. Cox made a ring type muffler and a slide type for the .09. Guess I'll have to dig out my Cox bottle and take some pictures of the Medallion .09 choices. There's also the chance the Queen Bee muffler might fit.

Andy,

If you want to use an electric starter DuBro makes a spinner type nut of about 3/4" for Cox and Novel engines. I bought one last week for my Norvel .074 and when I tried it I discovered the screw is too small in diameter so it must be for a Norvel .061. I'll drop by ACE hardware and see if I can match up a long screw that fits. Or....now that I have the $6.00 spinner I guess it gives me justification to pick up a Norvel .061.

AndyW

My Feedback: (1)

JMan,

Yes, the stock reed cranks are likely to break under the motivation of spontaneous combustion. One way to get around that, although I haven't run it yet, is to bore out the case to take a crank from a product car engine. These cranks were larger in diameter and the crank web was thicker.

You're on the right track on the issue of having much better compression seal for diesel operation. I tried to achieve that by electroless nickle plating old pistons and it worked till the plating started to peel. But, this was an amateur effort. I'm sure that with the proper chemicals to etch the old pistons properly I could get the nickle to stick. Or, maybe not.

My new strategy is to take .049 cylinders and hone them out for a squeaky fit for .051 pistons. Done a few, still working on that, honing skills and technique not up to par.

Can you do .010 and .020 pistons?

BTW, Cox was kind enough to send me a couple of .09 cylinders that were finished all around except for final honing. Out of two I managed to hone out a good one that was tight at the top and would stick if you hesitated, just like Norvels. This was installed on my RC .09 version. It's been run and throttles well but it may need a great deal more break in. Hope to do that soon. Cox is making a valiant effort to minimize break in time for the average guy but I'd prefer a tighter set up so that with care, you could break in for that perfect running fit. In the old days, with a well run in Cox, you'd get a nice polished look to your piston. These days the piston is stained with varnish/burnt oil indicating a looser than desired fit. Still, power is usually good so who'my to complain?

Dan,

I like how you think,,, got a spinner, Hmmm, needs an engine. I did get me one but on the intended plane it put the balance off even with the battery all the way to the back. Maybe if they made it out of plastic? DuBro?

Dan Vincent

Andy,

I never realized the Cox car engines had such a "Beefy" crank. I'll have to pull out that bag of Cox reed engines I have someplace. Must be a couple of pounds of them. There were at least two or three car engines in there. Why not just use the whole car engine, rather than boring out another case?

Also have a couple of Davis heads for Cox .049. one of them has an extra lever with an "O" ring to provide RC compression changes in flight. Seems to me once the "O" ring gets oily there goes thepressure needed to operate the compression screw.

Hey, come to think of it...there should be an .020 Davis head around here someplace. Once your memory goes you find all kinds of stuff you didn't know you had.

Wait...if your engine vibrated with the Dubro spinner...shouldn't you get another engine to make sure it's really the spinner? See...you can justify anything.

"Figures don't lie..but liars can figure."

AMB

OK Guys close to the pefect run? Went to the LHS picked up a MA 8x3 (Blue plastic) after starting backed out the compression screw
about a half turn (was running about 10500), After backing the screw out it turned 12100, head temp was about 270, Plenty of oil coming out the the exhaust and clear as glow, very slight grey smoke, this is the cleanest running diesel I have every run< great
transition, no burps and does not wander in rpm. The decathalon will love it martin
may even be better with Andy Ws prop
Had to do this this is for the Dingo folks Down under we have wolves here

AndyW

My Feedback: (1)

Martin,

The MA blue 8 X 3 sounds like a good match to the Cox. However, in the air tells the tail. Right now I'm looking at an ad for MA Electric Only Series props. Been wondering if these might not do OK on diesel. On glow, at the rpms they do, props need to be built to withstand the centrifugal loads. On diesel, at lower speeds, maybe they're overbuilt and their blade design is less efficient. Just as electrics turn more slowly with more torque, maybe diesels have similar characteristics?

AMB

I noticed their ad also, I wonder if they have a max/rpm limit, The geared electrics turn much slower than glow or diesel they run approx 3:1 to6:1 reductions, some of the direct drive brushless I do believe will turn in excess of 10K
Some of you folks ar running these what kind of revs do you turn with them? For our purposes the so called 280 thru 550 electric
equivalents should apply to the half A stuff. martin

Japanman

Thanks for the confirmation of the crank situation. I have a car crank- but to be honest with you comparing it to the stock crank it is only slightly stonger looking. I was thinking of making up a crank more along the lines of a norvel crank... I like the car crank and have it in a glow engine. I figure it is better to make something that is a bit of over kill as I`ve heard of people breaking the Davis diesel cranks too.
That said, this is all a bit pie in the sky for me know as I have a lot on my plate right now... but nice to talk converse idley about it anyway

J.M

AndyW

My Feedback: (1)

JMan,

Even a small increase in diameter translates into a substantial increase in mass, according to the math. Measuring off the screen, I got 10.3 mm diameter on the stock shaft and 13.5 mm on the car crank. This gives you a 30% increase in diameter. However, using pi to get the area, times the length will give you the volume of material or the mass percentage increase and that comes to a whopping 72% increase in mass for the car crank. But, I don't know if its the shaft that's breaking or the crank web. But that has been beefed up in a similar fashion so that should help a lot.

I did up my Black Texaco in the winter and had an exhaust throttle and diesel conversion made for it. In the spring, I tried to run it on glow and the darn thing would pop and fart but not keep running, despite a number of attempts. One try as diesel had the same result. [sm=confused.gif]

This thread prompted me to have another look. Under the light of re-inspection, it seems that the sealing ring at the stem is just not sealing. It's not prominent above the little flange, hell, it's not even flush. Note that this engine was cobbled together from my parts box. Plus, to be fancy, I used a black plastic backplate. So, I'm in the process of getting a proper O-ring; one of those round ones in cross section that will have a more positive seal along with a stiffer metal backplate.

Now, hopefully, I'll be able to run this reedie as diesel and see if that crank will hold up.

And Dan,

You're right, my faux pas,,, memory thing you know. I did try to bore out a stock case because the car case was ugly but my first try was a dud so while preparing to try again, it occurred to me that I could use the original case and it would be simpler to cap the ugly part with an easily made addition.

Dan Vincent

Andy,

That's a nasty-looking little dude. Looks like something Arnold Schwartzenegger (spelling?) would use in a Terminator movie.

I like your front end piece. You should make one that looks like it houses a BB and watch the rumors fly.

Are you using the teflon disc under the Davis head?

One other thought. Since a diesel sips a lot less fuel than a comparable glo, I'm wondering if a single groove Cox cylinder might run fine while the two groove type might not add all that much to the power output...something else to put on my list of stuff to try.

AndyW

My Feedback: (1)

Dan,

That was the idea, to make a mild Texaco look dangerous.

Or maybe just install ball bearings. I've done that with Norvels.

Actually, that's not a Davis head but my own cut from a Texaco glowhead. It uses an O-ringed contrapiston like the RJL head.

Yes, experimenting with differing cylinder designs might go a long way to optimizing the concept. If I can get the damn thing to run in the first place. [:@] And yes, in retrospect, as a diesel, that tank is going to be way too much flight time. But, I do have a throttle and can cut it to bring her down, unlike a stock Texaco.

Hey, the Texaco event was for duration on a specified engine. Had anyone tried to go diesel and challenge the rules?

Dan Vincent

Andy,

I think those SAM guys are pretty strict about their Texaco class. They want everyone using the same engine in Half-A.

Funny, You can use almost anything in A-Texaco. Some guys use an old 1.3 mills for gas mileage while others will stick an OS .10 on a small Playboy pylon and get it to altitude as quick as possible and then try to catch a thermal to keep it up there.

The little .020 Nostalgia class uses the Cox TD .020 engine. At one time there were some Canadian guys who wanted to use some of the miniature replica diesels in that class but the Cox engine rule was not to be broken. I never heard if they stated an outlaw class so they could use the engines they liked.

Don't know if a BB crank would do much for a reed Cox .049 except add weight. Those Cox product .049 came in both single and dual intake groove types. Most guys would grab the dual ports and throw the singles in their parts pile. With a diesel, there might be renewed use for the old single port cylinders. Diesels don't need monsterous porting.

AndyW

My Feedback: (1)

Hi Dan,

You're absolutely right about ball bearings in small engines. I've installed rear bearings into Norvels with not a single extra rpm for my trouble or any other advantage. MAYBE if I could find a suitable bearing for the front end, but nah, no point. Frictional area goes up proportionally with diameter and that may be why larger engines do better. With our very small shaft diameters, there's no need. But it was fun trying.

About a diesleized Texaco, well, it WOULD be the same engine and it could even be dieselized without any hint otherwise. Hope to do an article on that this winter. The sneaky person trying this would only need to make sure that no one smelled his fuel. [X(]

Dan Vincent

Andy,

Were you thinking of making a fixed head diesel out of the Cox .049 Texaco and using a brass slug and shims to get you where you need to be? Like one of Lou's "Gadget" brass plugs for a glo engine,

Yeah, the stinking fuel would give you away.

Everyone would wonder why you were turning such a big prop. Stay with the same diameter and up the pitch...much less noticeable.

I think the Texaco guys are just trying to keep the field level by having everyone use the same engine and fuel. Wonder how many of the engines are compeltely stock, without some procedure having been done to gain an edge. Seems to me the choice of model would have a larger effect than anything you could do to the engine besides having a bunch of them and then choosing the "Pick of the Litter."

AndyW

My Feedback: (1)

Dan,

Yeah, something like that.

gcb

The Texaco engine might make a great diesel conversion. The intake is smaller to maintain fuel suction while running a very large prop. That might help. A conversion head should probably have a bunch of fins for cooling (note the glow head fins).

Does anyone know for sure whether just a diesel head and new crankshaft, with no other changes is illegal for Texaco?

George

SGC

Basically yes, very little can be done in the way of modifications to a standard cox reedvalve motor. I have posted an extract from our MAAA rules which as far as I know are the same internationally.
Stewart

Japanman

"Aditional mufflers" would allow the use of a very long and specially made tuned pipe would it not?

J.M

AndyW

My Feedback: (1)

JMan,

Yeah, but not even a tuned pipe is required. That would attract attention. Using FlyQuiet tubing, you could make a long exhaust pipe and with the installation of a baffle at just the right spot, you could pick up some free rpms. Doing this on a Norvel typically adds 500 rpm. Did this on my .074 powered Tsunami.

But, all of this is NOT to encourage breaking the spirit and intent of the rules. Hopefully it'll alert the officials to keep on the lookout. But how would they check for a brilliant guy like Wink (t-kwink). Check out the thread, "reed valve engine update". His work has shown a decent rpm increase with the installation of bearings into a reedie crankcase.

Hmmm, maybe twin ball bearings in a Norvel WOULD make a difference.

AMB

Tried running a tornado 7x6 on the norvel 074 diesel conversion. not good, looking of the engine running from the side was showing a flex of at least 1/4 inch at the tip of the prop fore to aft at about 10000, just too much flex in the blades, the MAS 8x3 blue prop at 12000 has none (at least not to any degree that can be seen), The engine was not surging in rpm either martin

AMB

Finally, 10pm and got the 074 norvel diesel conversion in the decathalon it replaces the 061 Norvel, needed a little more punch
In the air tomorrow (weather permitting) martin