Author Topic: Tank height for side mount engine. (Read 7333 times)

Jim Svitko · « **on:** October 27, 2015, 12:29:21 PM »

With a side mount engine, either profile or full fuselage, what should be the vertical position of the fuel feed line in relation to the engine? With the rectangular wedge metal tank, I have seen the tank center line at the same level as the engine center line. Other times, I have heard from those who had to raise the tank (with the plane upright) to get equal engine run upright and inverted.

About a quarter inch above the engine center line seems to be the position most have settled on. If this is the required position then something is going on that I do not understand.

Mark Scarborough · « **Reply #1 on:** October 27, 2015, 12:32:06 PM »

I start with it about 1/8" above the venturi centerline and adjust from there,,

Terry Caron · « **Reply #2 on:** October 27, 2015, 01:28:31 PM »

Jim, the thread "Standard vent vs Uni-flo" may be of interest.
As I understand so far, the key factor is not tank position as such, but interior vent opening position relative to the spraybar.
But I must say, I'm still trying to sort it all out with help from the forum.

Terry

Mark Scarborough · « **Reply #3 on:** October 27, 2015, 01:33:28 PM »

Quote from: Terry Caron on October 27, 2015, 01:28:31 PM

Jim, the thread "Standard vent vs Uni-flo" may be of interest.
As I understand so far, the key factor is not tank position as such, but interior vent opening position relative to the spraybar.
But I must say, I'm still trying to sort it all out with help from the forum.

Terry

that is correct,, I am making my blanket statement with respect to a rigid tank, setup with fuel pickup and uniflow on the tank centerline

Jim Svitko · « **Reply #4 on:** October 27, 2015, 02:17:06 PM »

Quote from: Mark Scarborough on October 27, 2015, 01:33:28 PM

that is correct,, I am making my blanket statement with respect to a rigid tank, setup with fuel pickup and uniflow on the tank centerline

I plan to use the rigid metal tank. It is uniflow, and as I understand the placement of the inner workings, the back end of the uniflow is on the same level as the fuel pickup but it ends just a bit short of the pickup tube end. I never took one of these apart to look at the inside.

I run metal uniflow on upright and inverted engine installations with the fuel pick (tank centerline) at the same height at the spray bar. Maybe I have to shim a little, it varies at times. After filling the tank, I cap off the fill line and the uniflow tube protrudes from the front wall of the tank, right at the firewall. This set up has worked very well for me.

I would like to duplicate this set up with a side mount engine. From what I have been reading elsewhere, the fuel feed line (tank center line) should be about a quarter inch higher than the center line of the engine. I made two runs with the engine installed in the plane, tank at same height, and it runs OK but I can tell that the run is not as steady as with an upright or inverted engine. I can remove the shim to place the tank a quarter inch higher but that is as far as I can go. I will give this a try later in the week.

I should add that the engine runs were on the ground, I have not tried a flight yet.

Roger Vizioli · « **Reply #5 on:** October 27, 2015, 02:31:09 PM »

Jim,
I always start w/ the feed line in line with engine C/L.
Have rarely had to "tweak" same though I have raised / lowered tank with no obvious results.
"Your results may vary!"
ensure your uniflow inlet is directed in the line of flight for constant pressure. if angled it will cause a "variable" siphon effect depending on flight speed. (AMHIK)

Trust all is well!

Roger

Dave_Trible · « **Reply #6 on:** October 27, 2015, 02:53:53 PM »

Many of the older engines do pretty well with tank/pick up line on siphon tanks or uniflow end in uniflow tanks on center with the glow plug but many newer engines, notably the OS FPs and LAs run more uniformly upright and inverted with the tank vent centerline about 3/32" higher than the engine centerline. This has more to do with the internal design of the engine so can vary. Best bet is to allow for some field- adjustable set up and simply try it. I've used both slotted bolt tabs soldered to the tank or rubber bands with enough space to slide the tank up or down as needed. These are for metal tanks. If you permanently lock your tank into a spot Murphy says it will be the wrong spot.

Dave

Jim Svitko · « **Reply #7 on:** October 27, 2015, 03:11:35 PM »

The forward end of the uniflow tube on all my installations (full fuselage) is behind the engine, in somewhat "dead" air. At least, it should be "constant" or "consistent" dead air. I did not want the variability of going into the wind and then downwind. As I stated, this has worked out very well for me. Very consistent and reliable engine runs. I have never tried muffler pressure as I have never seen the need for it.

I now have a side mount engine, full fuselage, with the same tank set up.

When viewed from above, the fuel feed line is about a quarter inch outboard of the spray bar. I do not see how that could affect fuel delivery be maybe it can. I have seen profiles with the fuel feed farther outboard than that and they run OK.

Since most of what I have read and what some other have experienced, I will remove the shim and that will move the tank up (with the plane upright). I will see how that compares to the previous ground runs with the tank on the engine center line. Depending on the results of that shim removal, I will try a flight. Things might be different with the plane in the air.

Roger V: things are going OK. Staying pretty busy with trying to build and get in some flying time, as well as working on improving my Spanish.

Steve Helmick · « **Reply #8 on:** October 28, 2015, 02:54:35 PM »

Tank height will depend on whether you intend to run the engine on uniflow or if you leave the overflow uncapped and thus run as an "old fashioned" fuel system. A lot of guys say that Fox .35 Stunts particularly like the non-uniflow tank, because the engine then produces more power when leaned out at the end of the flight. Seems to me that the uniflow would always be better, because you'd have the same power and same speed throughout the flight, so your timing (pilot's timing) would be better.

Try muffler pressure to the uniflow vent. I like it, but some don't!

Steve

Air Ministry . · « **Reply #9 on:** October 29, 2015, 07:50:23 PM »

GENERALLY , the ground run will match the Air Run. maybe - with a Fox . I wouldnt know.

So with the thing a bit rich - hold it nose up, it should get a break/ increase rpms .

angle nose up . This is pretty baqsic and not that difficult .Ive found at the angle up ( 15 or 20 degrees , say )
its fairly obvious if the ' pick up ' has come in . In fact , you angle it up - to ' come in '.

If the angles a mile out upright to inverted , youd go and shift the tank , to rectify.

Chris Wilson · « **Reply #10 on:** November 01, 2015, 06:56:15 PM »

Quote from: Jim Svitko on October 27, 2015, 12:29:21 PM

About a quarter inch above the engine center line seems to be the position most have settled on. If this is the required position then something is going on that I do not understand.

Asymmetrical tank mounting is only required if you have an asymmetrical engine.

Try the same with a radial ported or symmetrically ported engine and tank height issues seem to be non existent.

Dennis Toth · « **Reply #11 on:** November 02, 2015, 05:30:20 PM »

Jim,
Generally you need to allow for shimming of the tank up and down on a profile to get the upright and inverted lap times the same. This can vary depending on the engine you are using. If you are using a baffled engine (i.e. Fox, McCoy, Veco) you would generally start with the tank center about 1/8" above the glow plug center and adjust from there. For OS FP's, LA's types you could start with the tank center in line with the plug center.

Start shimming 1/16" at a time, then when you get within a 0.1 sec upright to inverted lap times you could do 1/32" shims. Just for information with the ship upright as a referance if its faster inverted or in outside loops then upright, lower the tank; if faster upright or through inside loops then raise the tank.

Best, DennisT

Norm Faith Jr. · « **Reply #12 on:** November 02, 2015, 07:06:24 PM »

Hi Jim...I use a clunk tank on my profiles. I plumb them using a technique ( a type of "uni-flow") that I got from Brad Walker (Godzilla). I take the tank one step further using a technique I got from Dale McCord, by mounting the tank with RTV on a thin sheet of plywood, fuel proofed, with vertically, slotted mount holes. This allows the tank to be adjusted in the field, up and down, with very little effort. I've used this application for many years now and fuel tank problems became the least worrisome problem I've had with my profiles.

Lauri Malila · « **Reply #13 on:** November 02, 2015, 11:54:10 PM »

Quote from: Chris Wilson on November 01, 2015, 06:56:15 PM

Asymmetrical tank mounting is only required if you have an asymmetrical engine.

Try the same with a radial ported or symmetrically ported engine and tank height issues seem to be non existent.

That is not true.
I have an absolutely symmetrical engine and I can run it in both directions. The running symmetry issues reverse when I change running direction. Slowing after inside maneuvres when engine runs anti-cv turns into speeding-up.
Trying to compensate those with tank height is just another error compensating another.
I have kind of proven that the reason is not in scavenging, it has to do with fuel getting trapped somewhere in bottom end of engine.
It may also be a load thing; due to gyroscopic forces the engine is loaded differently in inside-and outside maneuvres. L

Chris Wilson · « **Reply #14 on:** November 03, 2015, 03:27:37 AM »

Quote from: Lauri Malila on November 02, 2015, 11:54:10 PM

That is not true.
I have an absolutely symmetrical engine and I can run it in both directions. The running symmetry issues reverse when I change running direction. Slowing after inside maneuvres when engine runs anti-cv turns into speeding-up.
Trying to compensate those with tank height is just another error compensating another.
I have kind of proven that the reason is not in scavenging, it has to do with fuel getting trapped somewhere in bottom end of engine.
It may also be a load thing; due to gyroscopic forces the engine is loaded differently in inside-and outside maneuvres. L

Hi Laurie,
Does your engine have radial or symetrical exhausts?

But I agree about the fuel getting trapped or condensating. Most dont realise that any two stroke carries far more of a fuel charge than can be used for the immediate cycle so it sticks or condensates where it can, usually in the transfer ports and is subject to G forces.

Heavy droplets can flick free during manevours, just picture rain droplets on a car windscreen slowly being pushed upwards as you move forward then hit the brakes - the condensated drops are subject to G forces and this has been shown with strobe light photography in two stroke ports before.

Cheers.

frank mccune · « **Reply #15 on:** November 03, 2015, 07:00:28 AM »

Hi Norm:

In the picture of your tank, the uniflow tube looks like it terminates against the outside wall of the tank and is quite a bit forward of the pick up tube. Is this correct and how well does this set up work. If it works well, it should make the additional fuel line and clunk weight obsolete thus making the tank easier to construct.

Be well,

Frank McCune

Lauri Malila · « **Reply #16 on:** November 03, 2015, 10:08:59 AM »

Chris,

It's a 4 port Scnürle without boost port. Rear exhaust. See the drawing.
One might think that rotating crankshaft causes some kind of a phenomen like circular flow or pressure difference that causes asymmetric scavenging but it's not really so. The problems do not reverse if I completely block the ports on either side.
Also, the feed from bottom end to bypasses is symmetrical because of 100% piston scavenging. Piston acts as a plenum chamber and should even all asymmetries before mixture is distributed to bypasses.
This is what happens: (with pusher prop)
-level- and inverted laptimes are same.
-when started from level flight or inverted flight, speed in both inside- and outside loops is same.
-engine speeds up slightly in intersection of figure 8's, when model turns to outside loop. It also accelerates slightly, for about a second, in beginning of inverted flight after 3 inverted loops.
I think this is a clear indication of some sort of fuel accumulation during positive G's. Then there is a burst of extra fuel in the system when G changes to negative.
Next time I dismantle the engine, I will take a close look at places where fuel droplets may accumulate, and eliminate them by rounding sharp corners, filling or by drilling drain channels.
But the issue is very small now, I can live with it. The more efficient the engine is (small venturi, more efficient head shape, running closer to peak power..) the smaller the symmetry issue is. At the moment it's so small that I chose to use pusher prop, it gives nicely extra power in top of figure 8 and hourglass without being too disturbing in horizontal 8.
I hope to have the problem solved in the new engine and model, cylinder will be tilted 40 degrees down from horizontal. But you never know..

L

Steve Helmick · « **Reply #17 on:** November 03, 2015, 06:00:26 PM »

Quote from: Lauri Malila on November 03, 2015, 10:08:59 AM

Chris,

It's a 4 port Scnürle without boost port. Rear exhaust. See the drawing.
One might think that rotating crankshaft causes some kind of a phenomen like circular flow or pressure difference that causes asymmetric scavenging but it's not really so. The problems do not reverse if I completely block the ports on either side.
Also, the feed from bottom end to bypasses is symmetrical because of 100% piston scavenging. Piston acts as a plenum chamber and should even all asymmetries before mixture is distributed to bypasses.
This is what happens: (with pusher prop)
-level- and inverted laptimes are same.
-when started from level flight or inverted flight, speed in both inside- and outside loops is same.
-engine speeds up slightly in intersection of figure 8's, when model turns to outside loop. It also accelerates slightly, for about a second, in beginning of inverted flight after 3 inverted loops.
I think this is a clear indication of some sort of fuel accumulation during positive G's. Then there is a burst of extra fuel in the system when G changes to negative.
Next time I dismantle the engine, I will take a close look at places where fuel droplets may accumulate, and eliminate them by rounding sharp corners, filling or by drilling drain channels.
But the issue is very small now, I can live with it. The more efficient the engine is (small venturi, more efficient head shape, running closer to peak power..) the smaller the symmetry issue is. At the moment it's so small that I chose to use pusher prop, it gives nicely extra power in top of figure 8 and hourglass without being too disturbing in horizontal 8.
I hope to have the problem solved in the new engine and model, cylinder will be tilted 40 degrees down from horizontal. But you never know..

L

If only you could double your fuel consumption, maybe the problem would become un-noticeable or insignificant.

My friend Dave Simons (he flew F1A, F1B and F2B, plus his son Hugh flew F2A & F2C) in Sydney had an early Yatsenko with inverted engine. He objected to "the Fox burp" and sent at least the engine/fuselage back to the factory, requesting that they change the setup to side mounted. He said he was a bit miffed when it came back canted to about 8 o'clock...but it ran much better and he was happy. I thought your earlier engine had bypasses carved into the outside of the cylinder? Did that not work well? FWIW, I'm thinking that the problem starts starts with the piston porting. I hope you have a good result with your experiments.

Steve

Lauri Malila · « **Reply #18 on:** November 04, 2015, 09:51:12 AM »

Hi Steve,

Yes I know those stories and those people. Also, there are engines that have opposite symmetry issues depending if they are mounted horizontally or cylinder down. In that case the best symmetry of running is found somewhere between those two orientations.
Strakhov had similar issues many years ago, and he ended up increasing bottom end volume.
Increasing fuel consumption does not help, quite opposite. It seems quite clear that best efficiency meand also best stability. Also, efficient burning and running the engine close to peak power also makes the model perform smoothly, especially in corners.
I know that nitro would help, as well as in-flight glow battery but they are not answers for the original problem.
I'm not looking for an easy solution, I'm more determined to find the origin of the problem and eliminate it.
Also the new version has the bypasses integrated in cylinder, they are just not shown in the drawing. But that kind of construction is much more stable than the usual thin walled sleeve. But I don't think it's very important. It mainly gives me more freedom in experimenting with ports.
I also think that full piston scavenging may have something to do with these issues, finding it out requires cutting the piston and cylinder.. I must think it well first. L

Norm Faith Jr. · « **Reply #19 on:** November 04, 2015, 11:13:06 AM »

Quote from: frank mccune on November 03, 2015, 07:00:28 AM

Hi Norm:

In the picture of your tank, the uniflow tube looks like it terminates against the outside wall of the tank and is quite a bit forward of the pick up tube. Is this correct and how well does this set up work. If it works well, it should make the additional fuel line and clunk weight obsolete thus making the tank easier to construct.

Be well,

Frank McCune
High Frank, the tube is actually pointed toward the outboard, fwd. corner of the tank ( Brad Walker's instructions shows that it should almost be pointed forward. The way I did it worked very well for me.) and terminates outside as the open, forward facing, tube. The over-flow is the tube that is plugged after filling, of course the fuel feed tube is connected to the clunk. I've run this on my Brodak .40 for many years and the engine runs are always predicable and consistent. Not my design...Brad Walker's. BTW...What TY said...is a fact. Don't squeeze the tank during start up.

Steve Helmick · « **Reply #20 on:** November 04, 2015, 04:18:03 PM »

Norm, could you please divulge the specific RTV product you use? Also, what cleaning, roughening, etc. that you apply to the tank? And what finish you apply to the plywood mounting plate?

Steve

Norm Faith Jr. · « **Reply #21 on:** November 04, 2015, 11:00:50 PM »

Quote from: Steve Helmick on November 04, 2015, 04:18:03 PM

Norm, could you please divulge the specific RTV product you use? Also, what cleaning, roughening, etc. that you apply to the tank? And what finish you apply to the plywood mounting plate? Steve

Hi Steve, The original idea came from Dale McCord out of Dallas...he used velcro, (I experimented with thick carpet tape also) in conjunction with the RTV, but I found this to be unnecessary and little cumbersome, it also contributed to fuel foaming. I use the following technique. I "lightly" scuff sand the surface of the tank with some 80-100 grit paper. Clean the scuffed area with solvent, acetone / MEK. I mount my tanks on 1/16" ply. I make the plywood plate big enough to fully accommodate the scuffed side of the tank with the plate protruding above and below (about 1/4 -3/8") the tank's perimeter (this allows for a good bead of RTV) and protruding enough fore and aft of the tank to again capture the RTV and allow for vertical slotting for the mounting fasteners. After the plate has been cut, slotted and fitted to match the fuselage, I clean the plywood with a clean cloth making sure there is no oil or grease. I mix up some 15 minute Devcon epoxie and warm it a little with my heat gun until it thins to a brush-able texture. I then completely cover the plywood plate. Let it cure real good. When cured, lightly scuff the side of the plate where the tank is to be mounted. Using clear General Electric (GE) RTV, (O'Reilly or AutoZone) apply a generous layer (1/16-3/32") of the RTV to cover completely, the scuffed area of the tank, align the tank on the plate and apply enough force to lightly extrude the sealant from under the tank. Allow the weight to stay in place until the RTV has reasonably cured. After the RTV has cured (this part is important) Apply a generous "fillet" seal of RTV between the tank and plate. You may want to mix a little Dawn and water. (70 h2o / 30 Dawn) Dipping your finger in the liquid "fair" the bead of sealant, making sure that the complete perimeter of the tank-to-plate area is sealed. Allow the RTV to completely cure. Plumb your tank, and mount it with your choice of fasteners. What ever fastener you use, it must have enough bearing surface to capture the slots in the plate. I use a washer under the fastener head. the fastener location remains stationary and when loosened, will allow the plate to slide up and down or at a alight angle if needed. You can paint the plate after the tank has been mounted, if desired. Like I had stated earlier, I've used this system for many years and "knock on wood" have never had a tank come off. Hope this helps and wasn't "long winded."
Norm

Chris Wilson · « **Reply #22 on:** November 05, 2015, 03:51:03 AM »

I do know that radial ported diesels of old (and new) when side mounted do well with the tank feed inline with the thrustline.

These are symetrically ported engines with just about every angle of pitch covered by a corresponding port.

A schneurle or side ported engine can not hope to duplicate this.

It would be interesting to see Lauri's engine try a true radial port system to seperate run assymetry from crankcase to scavenging.

Lauri Malila · « **Reply #23 on:** November 05, 2015, 04:14:08 AM »

What is exactly radial porting? Do you have pictures?
As I srote before, I have tried blocking the ports completely on either side of cylinder. It kind of screws up efficient scavenging but there was enough power left to find out that it had no effect whatsoever to the direction of running asymmetry.

Chris Wilson · « **Reply #24 on:** November 05, 2015, 12:58:22 PM »

Hi Lauri,
Oliver style or PAW porting.
I will dig out a picture though mate.

P.S. Probably a link to a good article may be better -

http://modelenginenews.org/cornell/p5.html

(Called reverse flow in this case.)

But we are a risk of hijacking this thread.

Steve Helmick · « **Reply #25 on:** November 05, 2015, 08:46:45 PM »

Quote from: Norm Faith Jr. on November 04, 2015, 11:00:50 PM

Hi Steve, The original idea came from Dale McCord out of Dallas...he used velcro, (I experimented with thick carpet tape also) in conjunction with the RTV, but I found this to be unnecessary and little cumbersome, it also contributed to fuel foaming. I use the following technique. I "lightly" scuff sand the surface of the tank with some 80-100 grit paper. Clean the scuffed area with solvent, acetone / MEK. I mount my tanks on 1/16" ply. I make the plywood plate big enough to fully accommodate the scuffed side of the tank with the plate protruding above and below (about 1/4 -3/8") the tank's perimeter (this allows for a good bead of RTV) and protruding enough fore and aft of the tank to again capture the RTV and allow for vertical slotting for the mounting fasteners. After the plate has been cut, slotted and fitted to match the fuselage, I clean the plywood with a clean cloth making sure there is no oil or grease. I mix up some 15 minute Devcon epoxie and warm it a little with my heat gun until it thins to a brush-able texture. I then completely cover the plywood plate. Let it cure real good. When cured, lightly scuff the side of the plate where the tank is to be mounted. Using clear General Electric (GE) RTV, (O'Reilly or AutoZone) apply a generous layer (1/16-3/32") of the RTV to cover completely, the scuffed area of the tank, align the tank on the plate and apply enough force to lightly extrude the sealant from under the tank. Allow the weight to stay in place until the RTV has reasonably cured. After the RTV has cured (this part is important) Apply a generous "fillet" seal of RTV between the tank and plate. You may want to mix a little Dawn and water. (70 h2o / 30 Dawn) Dipping your finger in the liquid "fair" the bead of sealant, making sure that the complete perimeter of the tank-to-plate area is sealed. Allow the RTV to completely cure. Plumb your tank, and mount it with your choice of fasteners. What ever fastener you use, it must have enough bearing surface to capture the slots in the plate. I use a washer under the fastener head. the fastener location remains stationary and when loosened, will allow the plate to slide up and down or at a alight angle if needed. You can paint the plate after the tank has been mounted, if desired. Like I had stated earlier, I've used this system for many years and "knock on wood" have never had a tank come off. Hope this helps and wasn't "long winded."
Norm

Thanks, Norm! I was enthralled...well, maybe not enthralled, but I appreciate the information. The local (very good) hardware store has dozens of different RTV products, some mere bathroom caulk, but some advertised as "adhesives". The latter seems like it should do!

Steve

Lauri Malila · « **Reply #26 on:** November 05, 2015, 11:55:54 PM »

Chris,

Let's not go 50 years back in development. L

Chris Wilson · « **Reply #27 on:** November 06, 2015, 02:06:00 AM »

Not sure what that means since Schnuerle porting goes back almost 90 years!

Norm Faith Jr. · « **Reply #28 on:** November 10, 2015, 07:19:08 PM »

Just received this from the author.
Norm

Andrew Tinsley · « **Reply #29 on:** November 13, 2015, 05:05:54 AM »

Hello Chris and Lauri,
For years I ran Oliver diesels side mounted and never a problem with upright and inverted flight lap times. It was only when I started using glows that the problem reared its ugly head. The comment about going back fifty years in development, seems a little strange, as the latest Oliver style engines, like the Alberto Parra Tiger 4 engines are very powerful, economical, give no problem with tank height and give a constant speed run. Sounds to me like a perfect set up!
I have and still do run an F2b plane with an MVVS 49 diesel and it gives a very pipe like run and is rock steady and repeatable. The only real drawback is the large variation in run time with small changes of needle valve position. With the latest rule changes to allow a fuel shut off, this is no longer a problem.
The real problem with diesels is that 99% of fliers reject them out of hand without ever trying them.

Andrew.

Lauri Malila · « **Reply #30 on:** November 13, 2015, 07:09:59 AM »

You should not compare diesels and glows, because of differend combustion process. In diesel, the combustion happens quite spontaniously in whole head area, perhaps even earlier near chamber perimeter. In glow instead, the explosion starts from the plug.
For this reason the squish band and scavenging efficiency is more important for running stability of a glow engine.
It may well be that one reason behind the (small) issues I have, are due to too efficient scavenging.
Look at ST or Retro for example, they are both horrible in thermodynamical and mechanical sense, with extremely turbulent scavenging and big thermal gradients. It seems that the gas flow is allready so fucked up that it is not possible to disturb it any more.
Chaos is one kind of a harmony.
L

Chris Wilson · « **Reply #31 on:** November 13, 2015, 04:39:46 PM »

Quote from: Lauri Malila on November 13, 2015, 07:09:59 AM

Look at ST or Retro for example, they are both horrible in thermodynamical and mechanical sense, with extremely turbulent scavenging and big thermal gradients. It seems that the gas flow is allready so f***ed up that it is not possible to disturb it any more.
Chaos is one kind of a harmony.
L

Well put Lauri, but its not about diesel vs glow.

Its about looking at a side mounted port system that works regardless of model pitch angle.

If I may be so bold as to state that your engine does not have all pitch angles covered evenly and symmetrically.
A radially ported engine, when side mounted does.

Mentally draw a clock face on your side mounted engines head and predict what 'times' or angles are going to be encountered during flight and they are probably not the angles that your ports will cover evenly due to engine rotation bias and gravity.

Most schneurle engines have the principle axis (9 o,clock and 12 o'clock) covered quite well and favour the 12 o,clock port through crank swirl but by the look of your engine the transfers are averaged out at 11 o'clock and 7 o'clock, and heavy bias on the exhaust at 9 o'clock but want about the minutes or hours in between?

What if you had a port positioned at every hour of the clock with an exhaust in between them, radially pointing to the centre of the bore? Would that not cover off every angle of pitch you could throw at the model evenly and symmetrically?

And if you accept that, would not the tank on a side mounted model be absolutely inline with the thrust?

But what I am curious about is where exactly does the 'clocks' angular center or centre of rotation lie?
It obviously is not the centre of the engines bore but could be reasonably assumed to be between the centre of lift and the centre of the manoeuvre.

You did ask for thoughts on this .................... and I have them

Chris Wilson · « **Reply #32 on:** November 13, 2015, 04:44:08 PM »

Quote from: Andrew Tinsley on November 13, 2015, 05:05:54 AM

The real problem with diesels is that 99% of fliers reject them out of hand without ever trying them.

Andrew.

Could it be the availability of ether also?