(CAD) 28 Cyl P&W R-4360

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not derailing my thread at all =) I love to hear the stories. I've heard it said that at a META power check in a maintenance hanger, if you were standing in the wrong spot you would be struggling just to breathe...one day I hope to experience the real thing, but until then, this is what I have =)

- Ryan
I may have already replied but I couldn’t find it if so then ignor me. I also ask forgiveness for spelling as I have a double vision issue that makes typing extremely difficult. Sometime a misspelled word completely changes the note . I do proof read with a magnifying glass but even that aid I still miss things.

so. I’ve built many rc scale warbirds. My handle should give a clue to my favorite.

your engine task is a daunting project. I don’t think anyone has built or even presented a cadd model of this engine. It was on my list but even with access to solid works I have stayed away. I do have the Hobson 18 cyl plan set and have reviewed it page by page. Then given thought to your project. When scaling models one thing come out quickly. That is not everything scales perfectly nor functionally. Cadd makes numeric things relatively easy. But when you transfer this to an operating machined engine it may not work out as you planned.

starting with the crankshaft is where I’d start too. Tom from Tom’s maker site has done a very nice job of creating and building an 18 cyl. Radial. On his cadd and cnc. Reading and looking at the Hobson drawings shows some great ideas as. The issue I see is that the engine may take many assembly steps and pressing the crank together may cause issues. Looking at Whitesbook you can see the complexity of it. Those movable counterweights may not be necessary as the vibration probably won’t be present as the material and proportionate strength, may not scale. Hobson only uses a 1.000 bore. So the piston is already designed as are the rings and assembly fixture. I looked at the two piece rod but I don’t think there is room enough room for a strong enough bolt without changing other things. The 18 cyl. crank has a splined insert crank pin. In real life it must have been a huge project to remove and replace this. I don’t know the torque needed. To get around this I look back on some drag racing issue we had with narrowed rear ends befor custom axels were made. A large axel was cut off near the flange then turned down to fit in a hole bored through the flange. This provided a bearing surface. Then the flange and axel were sssembled. Some were press fit then welded. The best were pressed then drilled on the hole line for a dowel,pin and welded. These were incredibly durable in the era. So for the new radial a slip fit could be made using the same feature it would be removable for assembly and disassembly. Modern two stroke small engines use press fit cranks.a hard prop strike or crash udualy knocks them out of slighnment or bends them. But some careful machine work would probably work on this model. Inventer may have some stress analysis available. I did a lot of this in industry with some expensive software. I even had vibration software. It’s been a long time since I even looked at my notes on this . I’d try it my self if I ever get out in the shop again. Doctor would probably commit me if he knew what I’m doing as it is. I’m not supposed to play any sports not even tiddlywinks . I ventured out to the batting cage . By using an eye patch I was able to hit a few pitches but I’m out of the game for good.

anyway. I just wanted to stay with you on this. I hope you can put up some screen shots as you go.

hood luck as you go on.

Boston museum of science has a cutaway R4360. It's a beautiful piece of engineering art. I could look at it for hours (but not so my wife....)

If you want to see the real thing, that's one place to go.

A quick Google search says that Lycoming's XR7755 was the largest radial engine. It never got past the experimental stage though.

From the website:

"The U.S. military’s naming conventions provide some info about the XR-7755: X stands for experimental; R indicates a radial cylinder configuration; and 7755 is the approximate displacement in cubic inches. That’s not a typo: 7755 cubic inches, 127 liters. There were 36 cylinders laid out in four rows of nine, each one with a 6.375-in bore and a 6.75-in stroke, displacing 215 cubic inches per cylinder."


Not to tangent away too far from the OP's topic, but....

The Lycoming referenced above is likely the biggest radial for US aircraft use, but the Russians had some big inline radials in marine service after WW2. 42, 56, and 112 cylinder versions of these engines saw service in various high speed craft. There is (or was, not sure if they are still active) a German tractor pulling team (Dragon Fire) using one of the 42 cylinder engines converted to alcohol.

Here is an article on the engines:
Excerpt from link:
Zvezda also coupled two 56-cylinder engines together front-to-front with a common gearbox in between to create the M507 (and others) engine. The engine sections could run independently of each other. The 112-cylinder M507 displaced 23,361 cu in (383 L), produced a maximum output of 10,453 hp (7,795 kW) at 2,000 rpm, and produced a maximum continuous output of 9,863 hp (7,355 kW) at the same rpm. The engine was 22.97 ft (7.00 m) long and weighed 37,699 lb (17,100 kg). The M507 had a fuel consumption of .378 lb/hp/h (230 g/kW/h) and a time between overhauls of 3,500 hours for the engines and 6,000 hours for the gearbox.

Zvezda engineer Boris Petrovich felt the 56-cylinder M504 engine could be developed to 7,000 hp (5,220 kW), and the M507 (two coupled M504s) could be developed to over 13,500 hp (10,067 kW). However, gas turbines were overtaking much of the diesel marine engine’s market share. Today, JSC (Joint Stock Company) Zvezda continues to produce, repair, and develop its line of M500 (or ChNSP 16/17) series inline radial engines as well as other engines for marine and industrial use.

Now back to the discussion....
Being a big drag race in my younger days and driving my supercharged Streetrod som 34k mile with no blower issues, I have looked at model engine supercharging. The only really successful mfg of supercharged engines is Conley. I don’t really know how much boost his positive displacement blower makes. Probably not a lot. It serves as a good fuel atomizer just as the street blower I had did. The issue is it’s hard to get much air flow into it and super tight clearances are required. Aluminum tends to fall up in a heart beat especially when hot. Gas is not a good lubricant.
the other issue is spinning it in its best envelope. Radio enginges have used turbo and centrifugal blowers for a long time. Even these have to be designed around close tolerance and highspeed rotation. I did look into compounding an two speed systems bu gear boxes an bearing get expensive fast and machine work gets beyond hobby shop capability. So it still becomes fuel atomization and supplying enough air. The Hobson enginges have a centrifugal blower but it’s mainly for distribution and atomizing. But doing much different than shown gets complicated fast. The 28 cyl is complicated enough to keep most awake at night as it is. I don’t think it would be a good idea to try and use exhaust to spin a turbo, it may over heat exhaust valves and seats. Then you run into the same issues we had years ago in drag racing. Burned pistons and dropped valve seats. It would not be fun repairing this in one of these radials.it looks was but remember this is very miniure model there are lots of finely machined parts so you could make a big mess. I think s dump would be a nice project. There are small engine Fumo available but cost might make them impractical. The farm tractor synod are pretty simple to duplicate. A little math could give realistic readings.

Yeah your right it’s my vision again. Hogs on has an impeller that looks like a centrifugal blower. It rotates at crank speed so does more mixing than pressure. I looked at s planetary gear box to over drive it but it’s just not really practical to do this in my mind. I don’t have the technology to develop much of a centrifugal multi stage system. It would probably be more difficult than the engine itself. I even thought of using model airplane electric ducted fans but it still takes a lot of engineering and testing. I not equipped to do this now. It was hard enough to create a supercharged Streetrod that was efficient and durable.
My big radial (2.3 litres) has exactly the arrangement you describe, with an impeller normally driven at crank speed, to act as a mixer, with a planetary gear which can be engaged to drive it at 4 X crank speed, in the hope that it might generate some boost.
My big radial (2.3 litres) has exactly the arrangement you describe, with an impeller normally driven at crank speed, to act as a mixer, with a planetary gear which can be engaged to drive it at 4 X crank speed, in the hope that it might generate some boost.
I’m glad someone else sees this correctly. There is nothing wrong with it. Domes what is supposed to. With a compound planetary you cold get considerably more rpm. That’s what I had in mind. Now adding a model airplane electric ducted fan to the intake would add considerable amount of intake air at some pressure so you might begin getting boost. This is beginning to look like the full scale. I stopped her as I just don’t have the test equipment to evaluate progress.you can begin to see what p&w engineers tan into. Next is inter-cooling. It’s easy to see why the p47 became so full of ducts-and exhaustpipes.my supercharged Streetrod had intake air temps of 200 deg F. A friend has nearly the same combination and same temps. Runs great but an inter cooler would help. They are another 3~3” thick so blower high becomes ridiculous. Boats use them however. Free cold water.
I doubt you could get more than a couple pounds boost even with fine engineering just too hard to make precision enough parts at this scale. Nice idea of your gearing
I ran a rudimentary test of my blower, using my milling machine to drive the planetary gear. At the mills maximum of 1800 rpm and the blower at 7200 rpm, the 1kw mill motor was struggling, but it was shifting a lot of air (against no back pressure).
I'll be happy if it makes enough boost to offset the extra load it imposes on the engine. It's worth it for the impressive howling sound alone.
I ran a rudimentary test of my blower, using my milling machine to drive the planetary gear. At the mills maximum of 1800 rpm and the blower at 7200 rpm, the 1kw mill motor was struggling, but it was shifting a lot of air (against no back pressure).
I'll be happy if it makes enough boost to offset the extra load it imposes on the engine. It's worth it for the impressive howling sound alone.
That’s funny. Probably why the my Streetrod 6_71blowr whistled pretty good when you got after it a bit. The funny car you could hear in the driver seat. If you couldn’t the blower need real stripping.

That’s funny. Probably why the my Streetrod 6_71blowr whistled pretty good when you got after it a bit. The funny car you could hear in the driver seat. If you couldn’t the blower need real stripping.


Spelling error again.
I meant re stripping putting new Teflon seal strip in it. I’m surprised it took that much power to spin.have to look at the crank to see if it could stand more stress from compounding planetary. I don’t know how much power these motors make. I’ve heard up to 10 hp.Rc model radials can make 15 to almost 20 spinning 32 inch props.I have a 5.8 cu in 2 stroke that can make well over 45 pounds thrust w it’s a 23x14” pitch 2 blade prop. I’m looking forward to see your progress on this big motor.

As a result of your interest in supercharging I’ve begun searching the internet for more info..
it doesn’t take long before you begin to see how complicated a simple thought can become. P&w probably found this also.with a huge engineering staf and equally large machine shop facilities they gained knowledge quickly. Systems became vey complicated. See p 47 details. Then with all the new oxygenated air how to get fuel into in the proper ratio became an issue.this is where the first throttle body fuel injection came to be. So far as modelers this is about where we are the carb is no longer an easy device to work with. There are small fuel injectors but an electronic management system is needed. More complications. You could go to mechanical fuel injection similar to what we use on top fuel drag racers. They are not exactly as easy as they used to be either. Various sensors are required . You could add an 02 sensor as I used on my Streetrod. But they add a couple hundred dollars right away. They do work. It was key to making my supercharged hot rod about as close to a daily driver as you can get. We don’t have much but a series of props and tachometer to work with in our complicated engines. .

mph boy I have really open the can of worms. I’ll stop here unless y’all want to continue. We spen hours doing this stuff in the hot rod shop. Sometimes things work, some times the day is taken up with trying to figure out why we have a blown up engine.LOL
Liquid seal pumps would be a simple solution to a low rpm, high efficiency supercharger. It has built in intercooling and could use fuel as the seal. They run forever as vacuum pumps. See Find Out How Liquid Ring Vacuum Pumps Work | Nash

Lohring Miller
You are right. I had forgotten about high vacuum pumps. I do remember the special oil was extremely expensive. These were used in the aerospace R&D area I worked in to create space type vacuums. We had a one cubic yard vacuum chamber in a dry room. It took forever to pull it down.the sides and door were flat so we’re subject to deflection due to high vacuum. I was tasked with calculating then verifying this.while not particularly difficult math it was much more difficult to prove by measurement. Sealing took special o rings purchased from Parker.the pump and motor made so much noise they had to be enclosed in a separate room extension. Guess who had to research and present quotes for exotic sound dealing materials. My fancy in the day computer worked overtime with this stuff. It was nice in a way as I got premium top of the line software and many training trips. I’m actually glad I don’t have this now. My mind has enough to do just keeping up here LOL.I’m now being pressured to get dictating software. I get all these health care offers so I asked about a secretary but insurance won’t pay for that…….yet. I want to go out in the shop but my doc says he will commit me if I do. Maybe I should just bring the shop to my living room.

It doesn't take a special liquid. Dental vacuum pumps use water.

Lohring Miller
It doesn't take a special liquid. Dental vacuum pumps use water.

Lohring Miller
You are noting water. Water is death in very high vacuum chambers.
Also I was in a govt sponsored military research facility there were only limited number of times you could go in and out of the dry room per shift. Less than 5%rh.you never got sick there but dry skin and dry eyes were issues we dealt with. Pure lithium and some extremely active electrolytes used in lithium batteries was common. You never touched anything with bare hands or any bare skin. The common joke was you wash hands before going into the bathroom as well as after. Then you had to spend dry out time in the air lock doorway. Both ways.You learned a new meaning to clean and dry working in this environment.
The vacuum pump I'm talking about is in a dental office where solids as well as liquids are suctioned up. Similar pumps are used on submarines where a variety of substances get sucked out of the bildge. The pump doesn't care. If you need a clean output, use another style pump. As a compressor some fuel spillover could be controlled to operate the engine as well as to form the seal. I'm not aware of this use. I think it would be an interesting experiment. Dental vacuum pumps have a controlled inflow of water that flushes out the seal area and gets pumped out. The same could work in a compressor.

Lohring Miller
Piston, Revision 0

Just worked 13 days straight, so I apologize for the lack of updates on this front. Today is a rare day off, before I go into another 12 days straight, and I'll have enough consecutive weekends to tell the company they can't designate me on the weekend of the 9th and 10th, so I can go to the (very nearby) Arlington Fly-In.

Today I'll try and get some of those dimensions I posted earlier, into some semblance of working dimensions to derive other stuff from. I would like to get the master rod started, but I need other things first.

Using the dimensions I recorded from the 'real thing' a couple weeks ago, combined with existing knowledge of bore, stroke, and compression ratio, I can figure out the dimensions of the cylinder. This will theoretically help me figure out the master rod length, and I can work from there.

So one of my measurements taken was the cylinder's height, which I placed at 11.5 inches to the top of the 'intake port' (This is the point on top where the intake is bolted in. The 4360's Intake is on top of the cylinder, and exhaust on the side). The following picture shows what that measurement actually means, highlighted in yellow. I can use this to figure out the scale of the shown drawing, then work out such things as valve sizes, the height of the cylinder sleeve, etc.


My printed copy of the image the above is excerpted from, has that dimension at approx 1.65 inches, giving me a scale of 1.65/11.5 or 14.3 %. Any dimensions taken from this drawing, divided by 0.143 should give me an approximate fullscale dimension, then divided by 6 gives me my scale dimension. To confirm this, I take a measurement of the piston, which we know has a bore of 5.75 inches, measures 0.82 in the drawing printout, which is 5.734 inches using my math - close enough for government work! And I'm former Air Force, I would know ;D

I will probably use this value to go back and work out some of my other dimensions that I was sort of guessing on, like the crankshaft. This drawing shows that as .43 inches, or 3 inches full scale, so half an inch at my 1/6 scale, and... I used .435 inches, so I have some work to do. (this was for the master rod journal) And of course a change here changes my master rod, so I'm glad I checked this now.

Moving back, I have decided to do a revision 0 mockup of the piston. Knowing the piston is 5.75 inch bore, I can correlate the two drawings I have that show the piston, to glean information on the wrist pin, and one view even shows a very clear outline of the master rod, which will help me later. The piston on the R4360 is hemispherical and has 4 rings, with one additional ring at the very bottom. The image shown gives a piston height of 0.59 on paper, or 4.125 at full scale, so .6875 (11/16) at my 1/6 scale. I can't quite make out the detail on the grooves for the piston rings, so I will just use an arbitrary for now, and call it 1/32x1/32, and space them roughly where they look in the drawing. I can blow it up later and get a slightly more accurate idea if I wish. Lastly, the hemispherical part appears to extend about .06 inches, or .4195, or .07 inches at scale, I'll go with the nearby .0625, 1/16th of an inch.

One minor deviation, the 1/6th scale puts the bore at a strange 0.9583 inches. I like to work with even numbers, so I would round this either to the nearest thousandth, or nearest fractional equivalent, which lets me choose between 0.958, or a fraction of either 15/16 or 61/64 (0.9375 or 0.953125 respectively) - 15/16 sounds nice and easy even though it's further from true scale, so I will use it for now. I understand machining is easier in decimals, but for now, it's easier for me to track the numbers if they equate nicely to fractions. This is being done in CAD, so they can always be changed later :)

So, without much further rambling, we have a piston of 0.9375 bore, that has a base height of .6875, plus a hemispherical addition of .0625. This piston has (4) 1/32" grooves for the rings, plus an additional one near the bottom. (Some math would normally be required to figure out how to make that hemisphere, but CAD lets me just do an arc consistent with three points, and then rotate that arc about an axis to get the 3d solid :) (I can then go back and get the radius of the arc if I need it - in this case it works out to 1.7890625 inch radius)

iso view:

side view to show hemispherical surface:

That will wrap up this post, but I'm obviously not done with the piston. It's all I can do from the one view in the patent that I was working from. Another view will give me the dimensions for the cutout for the wristpin, and the wristpin itself... and that will be my next post. perhaps later today, we shall see ;D

As always, comments are highly welcomed, as I don't have the machining experience to know if my decisions are wise! Would you have done something differently? Did I forget something important? Note this is Revision 0, or not-for-production; it's intended to get the basics down, and will not be made as-is. Rev0's are expected to be changed as other parts of the engine are designed and force changes in existing parts.

- Ryan

(edited to correct typos. who needs proofreading when there's a 'modify'?)
Above was a post about driving the Hobson impeller. It seemed to me that the power required seemed very high considering the size of the unit(blower) or mixer what ever you want to call it. I had considered something ver similar early in thinking of modeling the 28 cylinder. I’ve had supercharged streetrods for many years using the gmc roots superchargers. They do take a lot of power to drive very fast. Eventually the more or less stop pumping air above 8500 blower rpm. We ran them much faster but the idea was to get max boost as quick as possible to get the car moving off the line. This did work but high gear when the hemi way Erving high the bioethics was just along for the ride. As driver I had plenty of time to look around for the competition and sometime watch him drive on by.LOL. The solution was to reduce the fuel flow quickly at some given rate as there just was not enough air to mix with it. The big scoop on the blower helped with ram air effect some but not something we did much about as there were only a few options available and we had the largest available. The plan worked as we won our share of races especially 1/8 mile ones. Leaning it out each run produced better speeds and elapsed times. We just didn’t go far enough fast enough. Races won an pay at the end of the day was more important than setting records. We had our dhare but could have done better. .
So to continue. I considered multi staging and coumpoundkng centrifugal blowers but gear trains and gear boxes began being a concern. In order to better understand planetary gear sets and the possibility of adding supercharging to these cool engines I ordered a tamia planetary gear model. It just came today but I haven’t ventured into assembly or modification yet. This kit even includes a small electric motor do you can drive your creation. It was inexpensive so I though I could always get another and build a nice compound planetary drive based on this model. It really surprised me at how small the parts are. It shows a needle nose pliers but I done thing even Snsp on Tools has one this tiny. I have a reasonable education in automatic transmission in cars and we had a 3 speed manually operated. Trans in the racer so taking them apart and reassembling thenm is not an issue. All the plastic parts can be purchased in metal if you shop around. Ratio calculations are readially available on the internet. Mounting a carb on the intake side the blowing into another blower might be asking for a fire or mini explosion. I just saw this very thing on the internet so I think making a rotary valve carb like the old glow engines had would be best as could use a pressurized fuel tank it would operate much like our race care fuel injection. It’s called mechanical FI I to would take some careful machine work and some good o rings but they are available. Regulating fuel pump pressure might be a bit tricky but by running on alcohol rather than gas you have a much wider air fuel ratio to work with. Overly rich or lean usually doesn’t make much difference.alcohol is readily available even at Home Depot. It’s a bit pricy but many horrid shops have it too even E85 would work fine I think.
I’m going to work with this micro miniature thing and maybe get another so I can compound it easily. Worst care the gears can be drawn in cad an 3 d printed pretty reasonably.
Anyway I’d like opinions and maybe more testing results. I saw a blower made from PVCpipe pieces a. Purple days ago. I may have saved the site I’ll have to look.

. I would suggest 3 d printing parts as you go the effectbiscthevtime saving . If you make a mistake you don’t have to worry much about the time spent machining a mistake it about like what was said when we first started 3 d modeling even in wire frame .it was easy to just push delete and start over . Scrapping a week work in the machine shop was harder to explain lusvitvgivesvthevsbilitybtobtestvfitvandcassemble You may miss or rethink something and just print new . You may want to consider a 3 d printer of your own costcwisectheybhsce come way down in price and set up pretty easily . Things like superchargers don’t scale very well even compounded it’s hard to get the air to just flow. I might suggest a modification for you . Create a pair of gmc type diesel blowers and either stack or plumb then compounded. There are a number of already modeled ones I think in grab cad Centrifugal and turbos just don’t work well a number of these have been made an most can’t inflstva plastic bag
Crankshaft, Revision 0

After reading all of the fun language that is a patent, two sayings came to mind. One, I've heard a few times in the various places I've been reading about machining engines. The other is a fairly popular one. Nike's "Just Do It", and "Start with a chunk of metal, and machine off anything that doesn't look like a [insert part, in this case crankshaft]"

A Crankshaft is effectively a long cylinder, with additional cylinder offset from its center line by 1/2 the length of the stroke. Where these offsets are, the main cylinder is cut away, to permit the rod for that crank throw to pass through the crankshaft's center line (If it couldn't, your engine wouldn't run very long. Half a turn at most.)

I have no information to go by for how thick the rods are. But what seems like a good guess to me, is about half of the diameter of the piston. My pistons are 0.9583 inches bore, so I'll use 0.479... naw, we'll just make it a half inch thick. I can always drop it to 3/8's later if I need to. If my rods are a half inch thick then by necessity my master rod journals need to be a half inch long, perhaps slightly longer. I'll add 1/32th of an inch to either side as a sort of buffer. Now, the patent drawing for the sideview of the crankshaft (patent is no. 2,426,879, I'm referring to Figure 21) shows lots of fine details, but being a patent, doesn't have dimensions. One notable thing is that the centerline bearing journals are bigger than the master rod journals, thus the 'long cylinder in the middle' is bigger than the master rod pin diameter. I can infer from a scale, assuming the patent drawing is to scale, that the diameter at the bearing is about 35% larger than that of the master rod journal.

... I talk a lot.

Anyway, while measuring that tidbit I found that at the scale I happened to print this image, the width of the crankshaft master rod journal pins is actually a half inch. this is a bizarre coincidence, but I'll take what I'm given! I can use this to get some other basic measurements with ease.

Anyone who saw my original post in the Questions thread regarding split gears will understand that I'm going to likely run into issues if I make this a single piece crankshaft. For now, I will design it as single piece, because it will give me a better visual idea of how I might be able to split it for a multi piece.

A basic layup of all those 'cylinders':



Obviously something's missing - there's nothing nearly strong enough actually holding the m/r journals in place but a thin piece of metal. I did warn that it was a basic layup. Of note in the second image is that each row is offset by 180 degrees, plus the offset between cylinders, of 12+6/7 degrees. this works out to 192.85 and change degrees, which allows each bank to fire on the opposite side of the bank before it, thus evening out vibration. This will make more sense when we get to firing order much later. (A preview of the firing order is visible at http://moozorzica.com/engines/4360order.jpg)

After some basic touchup, we have something that looks a bit more like a basic crankshaft :

This seems workable for now, so I'll leave it at this. Being as this is the first part, it's subject to great changes... hopefully not too badly, though.

I tried to keep the design minimal. I could have done the interconnects in that crazy half-round style they like to do, but this method will be way easier to machine, and will also lend itself to breaking down into multipart easier.

Based on this, I have : master rod thickness: 0.5", master rod journal diameter 0.435", master bearing diameters 0.5", 1/32" buffer on either end of master rod journals, all appropriate angular offsets between rows, etc. The overall crankshaft ends up being 7.200" long in its present design.

Next up: master rods. These are two-piece designs, that clamp together around the master rod bearing (which are also split bearings but I am leaning towards a multipart crankshaft, in such a way that i can slip the m/r journal bearings in one piece, way cheaper that route) and will require attach points for the other 6 slave rods, in each row. The Wasp Major has two of these actually passing through the bolts that hold the m/r halves together, which I'm sure I can manage, but will require custom made bolts.

This is enough for tonight. Thoughts on whether this would be machinable as one piece? a lot of pieces? Think I'd just end up making a bunch of scrap pieces in the process? I'd love to hear from you.

- Ryan

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