The effects of too little castor oil in a fuel mix is well known.  What are the effects of too much castor oil in the fuel mix?

        Tla,

        Frank

       The effects of too little castor oil in a fuel mix is well known.  What are the effects of too much castor oil in the fuel mix?

        Tla,

        Frank

     There is no simple answer to your question the way you phrased it. Way too many variables. How much are you calling Too Much? Opinions on this are all over the map, and that remains true even if you included some qualifying data, like: What kind of engine? ABC? AAC?  Iron?  ringed?  lapped? ball rearing? Bushing? Glow? Diesel?. What application? Like: Stunt? 2-2? 2-4? Pipe? Muffler? Racing? Speed? How much Nitro?
     Randy's general tips on fuel in the pinned section are good safe starting points. Non precision, older, iron piston engines are definitely happier on more castor and some of them actually go faster on all castor fuel in high performance applications.
     In general, if you use more than needed for a given engine type it will cause more gum and carbon. Some claim fuel flow issues in the cold but I flew stunt planes in the 60's in the Eifel mountains in Germany when it was below freezing with snow and never had an issue before synthetic oil was available. Our fuel there was 20% castor and 5-10% nitro (Fox 35 stunts, K&B greenheads, and McCoy 35's)

Frank,
Generally, up to about 30% will work. This was an old trick some used to trim compression (worked well in fix compression diesels) since the oil for the most part doesn't burn or add to the power it takes up space an adds compression. In a way that's what Fox used to get the 35 to run better, plus the extra oil carries away some heat.

So how much castor did you add to get to the point it would not run?

Best,   DennisT

  Define "too much" castor oil?  You don't mention what engine. You can't compare model engines to what you mix for a chain saw two stroke. The oil for the chain saw may be a concentrate. I have run certain types of oil in my vintage dirt bikes at almost 100:1 as per the factory recommendations with no problems, but I generally run it less than that. The oil that I run in those is a concentrate. If you know what works well in your engines, just stick to that and be happy. Why waste time, oil and glow plugs experimenting just to see what happens. At our ages, we can't afford to lese any of each!!!
   Type at you later,
   Dan McEntee

I have most always run more oil than what others are doing with no bad affects.  I'm sure there is a point with most engines where you gain nothing and may cause issues.  I have been puzzled over the years why people try to get away with as LITTLE oil as possible.  (?)  Oil is cheaper than new engines. 

      I am not sure about anyone running as little oil as possible, but you can certainly get smoother runs and/or more power withe less oil, assuming your engine can safely handle it. And, you don't end up varnishing up the insides, taking your tenth of a thousandths fits of an AAC cylinder/piston and gumming it up with .002 of sticky residue.

   More oil = more fuel viscosity = more fuel system drag.

   Frank did not mention what engine he is talking about. Fox/McCoy/Johnson, can tolerate or require a huge amount of oil, and the Johnson used a sintered iron piston that *required* varnish/carbon buildup to seal.  Clearances were super-sloppy. You RO-Jett AAC cylinder has clearances measured on the order of .0001" from the factory, trying shear castor oil with that creates tremendous drag. My engines won't even run reliably on Powermaster GMA fuel (22% 50/50) or similar mixes. It will run on Powermaster RO-Jett with 17% low-vis synthetic/5% castor), and it won the NATs on Powermaster "Sport" fuel with 17% total oil.  I have been running the same cylinder/piston assembly since the 2007 team trials on, for the most part, 17% oil with 3/4 synthetic.

  Similarly, we have abundant evidence that fuel line drag causes all sorts of funnies on a stock PA NVA with the usual Prather "medium" tubing on a range of engines, relieved by reducing the drag, or again, *running less or thinner oil*. We solved several independent "flame out" issues on PAs by running fuel with 17% straight synthetic. I have had to assist at least one person who, after running a RO-Jett 76 with a bunch of added castor (up to Fox Superfuel proportions) that could not be started in cool and humid conditions because it was so varnished up that the piston was sticking halfway up.

   So, to answer the question, every time we have tried running less or thinner oil, or reduced the fuel system drag, the engine ran better, or in some case, was necessary to make it run at all. I can't tell anyone else what their particular engine and fuel system setup needs, but we are trying to compete with what amounts to stone knives and bearskins, so you cannot afford to give up any sort of performance or run quality/run control. I have seen exactly zero ill effects in terms of wear down to - so far - 17% total oil, straight SIG or Powermaster RC sport fuel straight out of the can, or SIG Syn-Power.

     That's why.

   Brett

I generally use 23% oil in the RO Jetts.  That is 50/50 castor/synthetic.  I do run on the low rpm scale with long pipe and more pitch which COULD be some of the difference-Brett you run on the higher rpm scale by comparison.  When I back off the oil OR use a heavier synthetic mix the engine runs sound different and feel more uneven and when they do break (not too often for me) it is not as predictable.  I have had all four .76's rebuilt but the issue there has been scratching internally due I'm sure from my flying field which is an ancient sandy river bottom with some blowing dust in the air sometimes.  Even with the panty hose enough gets through so that a re-hone and oversize piston is in order every few years as well as new bearings.  I wish I could rig screen material similar to what is in the fuel filters over the venturi.  It may be fine enough mesh to make a difference.  I've tried those foam things-until the big Jetts suck them in.......

Dave

I unequivocally agree with everything Brett mentioned. At last year’s NATS, Dave and I overhauled my 75 setup and it fixed the *very* small issues I was having with my setup. This was the drilled out NVA, larger Venturi and big fuel tubing. This fixed the minor surging I was having in undesirable places in the pattern.

   It's a very tiny effect, and it just fixes a few little "funnies" here and there, "funny" being defined as inexplicably breaking in to a two-stroke for a few fractions of a second here and there. It's not as smooth as the Jett 61, but it's not like the random throttle blip effect that always plagued us on the PA61 and David had now and then on the 75.

  Note for those reading this - the spraybar modification is unique to the PA, not the Jett (any of them) because the the original intent was to replicate the Jett spraybar. Although the needles are the same thread and effectively interchangable* the spraybar OD is different, so you can't just put a Jett spraybar in a PA. Also, I tried the same sort of modification to enlarge the inlet side of the Jett, and could tell no difference, maybe because I am running 3/4 the fuel that you run on the PA, and maybe because it is bigger to begin with and I could only get about .005 more diameter out of it.

     I don't encourage anyone to do this modification who doesn't (1) know *exactly what they are doing*, (2) have a NATs Top 5 quality run already as a baseline, which is possible with a completely stock PA75, and (3) have an unmodified spare spraybar or spraybar(s) in case they screw it up. No offense to anyone, but I think that narrows the applicability to  about 5 people beyond David, Matt, and I.

    Brett

*There's one intentional difference between the PA and Jett needles - the Jett needles are only threaded the bare minimum to bottom out on the seat, and the PA is threaded far beyond that. The effect is that on the Jett, the teflon washer runs on the smooth part of the needle rather than the threads, hypothetically sealing better. I have several PA and Jett needles, and there are unintentional differences in the shape at the pointy end, within reasonable tolerances for grinding a thin steel rod, but enough you can tell the difference. I pick the ones that have the smallest/pointiest ends for better response. I ran both the bare ones and the threaded ones, after a few cycles, it cuts threads into the teflon, they don't have any difference and do not leak.

installed the spigot in a fresh #7 Venturi and put it back on the bench. The result was about 500 more RPM and similar run time on the bench as well. The needle was also screwed in about 1 1/2 turns from where it started and wasn’t as sensitive to movements.

It’s fascinating stuff and fun to experiment with!

Just curious. What is the ID of a "#7" venturi?

  Drilled or reamed to a diameter of #7 AWG, IOW, a #7 "number drill", 0.201". This is not a particularly large venturi and presumably contains a spigot of the usual configuration, too. The 75 could "pull" much, much more. But this is the range it runs in David's setup.

    I also note that the diameters of drills 4-8 are 0.2090", .2055", .2040", .2020", and .1990". I don't know what size venturi Matt had before, but I have run all those diameters on the RO-Jett, and a .002" jump from say a #7 to a #6 is clearly detectable, from a #6 to a #5 is a very distinct jump. I can set my engine up to work best with any of those, but there are changes to a lot of things to get it all working together. I settled on the system setup around a #5, after trying all those sizes (and the original #12 with no spigot).

      Compare and contrast this with almost every other thread about venturis, where people are jumping around by 1/16" or larger a step, replacing a .257 with .273, or factors of two on the choke area. Do that and you have no hope of figuring out what is going on.

    Brett

  Drilled or reamed to a diameter of #7 AWG, IOW, a #7 "number drill", 0.201". This is not a particularly large venturi and presumably contains a spigot of the usual configuration, too. The 75 could "pull" much, much more. But this is the range it runs in David's setup.

    I also note that the diameters of drills 4-8 are 0.2090", .2055", .2040", .2020", and .1990". I don't know what size venturi Matt had before, but I have run all those diameters on the RO-Jett, and a .002" jump from say a #7 to a #6 is clearly detectable, from a #6 to a #5 is a very distinct jump. I can set my engine up to work best with any of those, but there are changes to a lot of things to get it all working together. I settled on the system setup around a #5, after trying all those sizes (and the original #12 with no spigot).

      Compare and contrast this with almost every other thread about venturis, where people are jumping around by 1/16" or larger a step, replacing a .257 with .273, or factors of two on the choke area. Do that and you have no hope of figuring out what is going on.

    Brett

My old setup was a #9 spigot. The Venturi that came with the 75 is a #13 (.185”). A stock 75 setup is about as idiot proof as it can get. I started experimenting little by little over the last 3 years and have worked my way more towards David’s setup. Curiously my fuel consumption has improved when I switched to Dave’s setup despite opening up the Venturi, NVA, pipe, fuel tubing etc.

The all/mostly synthetic fuel is another change for the better on my setup…once again thanks to David. I should’ve listened closer to him years ago!

I'm interested in hearing the spray bar drilling technique, as well.

Regarding low oil, the Team Race folks have experimented with that in order to get maximum fuel economy.  Don't recall every detail, but the general idea was to reduce oil content until the engine wear was barely tolerable.

It was mentioned that the spraybar was drilled. What drill size is used? Do you drill all the way through or does the sparybar being drilled have a seat that the needle goes into that should not be drilled through? How far do you drill in?

    I knew I was going to regret that. No one reading this should drill, grind, or machine anything on their engine, the chances are astronomical that you will screw it up and negligible that you will note any improvement. The exceptions already know who they are, they are running 5-port PA75s on Eather pipes using David's setup, and even then, most otherwise identical systems are not sufficiently refined to note any difference.

    If you want to experiment with the reduction of fuel system drag in general, *use less oil* or *use thinner oil*. We know for certain that as long as nothing else is wrong, you can run 17% straight synthetic more-or-less indefinitely, thick or thin - on modern piped AAC engines. That means PA and RO-Jett, nothing else. Such a mixture will quickly destroy most of the engines used for stunt in the last 60 years.

      Even then, you have to have a reliable baseline system that is proven over seasons of consistent operation to be able to evaluate the effects on the run. The easiest way is to baseline your system with 17% oil fuel like PowerMaster RC "Air" (the regular RC Sport fuel), and then, when you are fueling it, start by sucking up a small amount (a percent or two) of straight Klotz KL-198 straight from the bottle, then suck up the regular fuel and flil the tank with the mixture. It will take tiny amounts of the oil, but just fueling the airplane will mix it just fine. Then compare.

    I apologize in advance for all those people who are going to ignore my admonition and drill a hole in your engine, and destroy it in the process.

      Brett

Brett,

To set your mind at ease, I am going flying later today.  I will use an O.S. LA 46 with a common, undrilled ST NVA.  I may also run a Moki that has an unknown NVA.

That said, I'm a curious person and wonder what the before/after I.D. of the spray bar was in your experiments.

   Note that I am not letting my head explode from the ST Needle - which is bigger enough than a PA that it won't make any difference on a 46LA.

      I note that David (and now presumably Matt) are using 8.5+ ounces of fuel for a 5:45 flight, your 46 is probably more like 4, so the flow rate is half and much less prone to "choking".

     I caution everyone because even David screwed up his first spraybar in an attempt to increase the bore  - as Dennis suggests, it can only go so far or you will drill out the seat.

    I presume I have now sold a bunch of new spraybars.

     Brett

  9 to 7 is a pretty big change. Depending on how far you pushed in the spigot, the #7 might be close to the original choke of the unobstructed venturi, so that is a good test.

     All of these options have tremendous fuel draw while still providing lots of power. We run larger venturis on 61 and still larger on 40's, which makes them much more "on the edge". That was the original idea behind David's 75 setup - try to get it to run as smooth as the Jett by running a smaller venturi, relatively small prop, and count on the extra displacement to make up the difference. I have run the 13-4s on the Jett, is has no issue with pulling the prop, and it's just a toothpick for the 75. I don't like the turn with the 13-4, so I went back to the 12.5.

      Brett

David had mentioned at the NATS that the new 75 he had in the plane was running a much larger Venturi, like a #3 or something like that. I could be very wrong and mistaken but that’s what I remember him saying.

I started running the David 13-4 prop just a couple months ago and it drastically improved the corner compared to the four blade I had been running the last few years. I want to try a 12” four blade still compared to the 12.75” I had been running and see if it is any good compared to the 13” eather. The corner on the 13” eather is pretty awesome though, not sure I could replicate it on a small four blade

   On the topic of venturi sizes, none of these are anywhere near the limit. He can correct my recollection, but when Frank W. came up with the spigot venturi, I think he said he was running a .250 (not a misprint, 1/4"!) on a PA61. #3 is a mere .213. 

   You were running a 12.75 4-blade?  I am not surprised the 13-4 3-blade cornered better.

    How big is that airplane?  Mine is pretty big and I have noticed a significant difference in cornering (tightness and quality) between the 12.5 and 13 3-blades even on mine. And the last time we did a fly-around David commented that "you could hit the corner as hard as you want and nothing bad happens" or some such. You will definitely give up vertical performance - but it's a ** 75  **, how good do you need the vertical performance to be?

Frank is awesome! He came to Dallas a few years ago with a pipe that had no baffle. It had the loudest 75 run I had ever heard. Ear piercing! Frank told me that’s how he likes it!

That airplane is pretty big. 64.5” span and 719 squares. But it’s a little heavy at 70oz. I was running 4.1 on pitch but it really needs to be at least 4.2 for a really good hourglass. That’s always been the weakest part of that plane’s flying capabilities. It’s outstanding everywhere else. The 3 blade also removed all the yaw I had with the 4 blade (to be expected). Not sure how much you were watching when we flew together the night before the top 5, but I was pushing the plane as hard as I possibly could and it yawed everywhere. Tripod videos between the sole top 5 flight and last time I went flying  of a much more crisp corner, and no visible yaw.

The new plane is slightly smaller, 63” and I think 690 squares. It’s also much lighter and will be 61-62 when I put it all together. I made some changes to the design that would be better suited in a different thread (or offline) rather than further leading this one astray. I hope it will help with vertical performance and presentation a bit.  Should have it done next week

AirMiseries,

To continue your aside:

"Back in the 70's Clarkson was experimenting with oil % ages for Goodyear & Team Race .
They found 12 % castor the muinimum , & 5 % synthetic . But they were after engine performance . NOT Life . So the Motors Did Not Last to long . They just didnt sieze . think it was the Ucon Snowmobile Synthetic ."

Can you clarify the total oil package? Was it 12% castor and nothing else in a glow fuel configuration, or was this in diesel fuel? Or was it 12% castor plus 5% synthetic in a glow fuel mix? Or was that package in a diesel fuel mix? Or was it 5% Ucon with nothing else added? (Whooboy!)

Diesel fuel (kerosene) itself has significant lubricity, as compared to methanol.

And if the tests were done in the 70's, are we to assume that it was an iron piston in a steel sleeve? Or an aluminum piston with a ring in a steel sleeve, or was anything chromed?

Finally, if the rod wasn't bushed, and maybe not drilled for an oil hole, that may have been the weak spot in the "minimum oil adventure."

More details from your voluminous attic are requested....

And, back to another aspect the original poster brought up, talking about how little oil can be used in two-stroke motorcycle engines and chainsaws et al, I would note that all the ones I have taken apart had rolling element bearings in all the critical places. There are lots of reasons that these do not require near the lubrication of the plain bearings (journal bearings) that are common on model engine rods and many crankshafts on older or less expensive engines. My thought is always this: for those that dream of running 100:1 in your OS .46LA (or insert favorite IC gem here), would you try running a gallon jug of fuel consisting of 128 ounces with only an ounce and a quarter of any type of oil someone has convinced you to buy? That's just over two tablespoons worth. Yeah, I wouldn't either....

The use of high silicon aluminum pistons changes things somewhat. As does hard dense chrome. And people have experimented with diamond-like coatings. All with the same idea to avoid galling and metal transfer between two rubbing surfaces that do not have a continuous oil film during operation.

The Divot

GOOD QUESTION . !

https://stunthanger.com/smf/engine-set-up-tips/fox-35-hemi-head-7541/msg63779/#msg63779

https://stunthanger.com/smf/engine-set-up-tips/fox-35-hemi-head-37393/msg382031/#msg382031

read the last post in each . Might Pay to PIN the HEAD or suchlike ? .

=========================================================================

 

Roit ,

Clarkson & Cronnies , This From Memory , Definately a MVVS D-7 & I think K&B dieselised & perhaps early Nelsons . All IRON / MEHANITE . DIESELS , so has the Kero , Maybe Jet Kero .
maybe the magazines around , but theyre scattered . So verbatum is difficult . Unless https://rcbookcase.com/categories.php?publisher_id=6 Id be  1974 /76 Id Guess .

A THING they disc overed ( Wot Stockton / Jehlic KNEW ), was the drum Induction that thew the fuel UP , missed the BIG END , which suffered from indirect flow in cooling & lube .
Thus the reversed Tee Dee center feed allowed lower lube % .

 

Spent the week  putting a S Tigre 60 set up in the Typhoon . the OS 80 had the same DRUM induction . Finally got a good ' proving flight on it - But was a pig to start etc .
So a major rework of the front end , and 12 ounce Vs 20 ounce - So theres no ballast forward . Way Forward . But might let the glue dry for a week .
Im not sure the Max 80 will be the latest thing in Control Line Aerobatics .
Combat wings built with PVA in winter in a week , were best not flown that weekend , tickly in damp conditions , as things wernt quite set .

Frank is awesome!

    Indeed - anything he says, you ought to listen to very carefully!

    Brett

So what is your clear oil, Dave, which brand? L