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KIMURA
04-04-2007, 03:47 PM
"my" R-2800 so far, built with an industrial CAD progi. The tricky point now is the situation of the planetary gear. As a template and aid while building that baby I got some pics from I-net and drawing from books like "Allied Aircraft engine of WWII" and "Major Aero Engines of WWII". But on some things these drawings do drop some details. Do someone have further details on the planetary gear?

The gears appear in that strange gold/yellow because I defined them as yellow zinc-plated/passivated.

http://mypage.bluewin.ch/a-z/kimura-hei/B1.jpg

Here a closer shot of the situation. This is stil WIP. Gear diameters may be change for correct gear ratio as soon as I get detailed info.
http://mypage.bluewin.ch/a-z/kimura-hei/B2.jpg

KIMURA
04-04-2007, 03:47 PM
"my" R-2800 so far, built with an industrial CAD progi. The tricky point now is the situation of the planetary gear. As a template and aid while building that baby I got some pics from I-net and drawing from books like "Allied Aircraft engine of WWII" and "Major Aero Engines of WWII". But on some things these drawings do drop some details. Do someone have further details on the planetary gear?

The gears appear in that strange gold/yellow because I defined them as yellow zinc-plated/passivated.

http://mypage.bluewin.ch/a-z/kimura-hei/B1.jpg

Here a closer shot of the situation. This is stil WIP. Gear diameters may be change for correct gear ratio as soon as I get detailed info.
http://mypage.bluewin.ch/a-z/kimura-hei/B2.jpg

VW-IceFire
04-04-2007, 03:49 PM
Holy cow! Thats bloody impressive!

I can't offer anything to help but I'd just like to say how amazing that is!

Redwulf 32 - Nis
04-05-2007, 04:57 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by KIMURA:
"my" R-2800 so far, built with an industrial CAD progi. The tricky point now is the situation of the planetary gear. As a template and aid while building that baby I got some pics from I-net and drawing from books like "Allied Aircraft engine of WWII" and "Major Aero Engines of WWII". But on some things these drawings do drop some details. Do someone have further details on the planetary gear?

The gears appear in that strange gold/yellow because I defined them as yellow zinc-plated/passivated.

http://mypage.bluewin.ch/a-z/kimura-hei/B1.jpg

Here a closer shot of the situation. This is stil WIP. Gear diameters may be change for correct gear ratio as soon as I get detailed info.
http://mypage.bluewin.ch/a-z/kimura-hei/B2.jpg </div></BLOCKQUOTE>

Impressive indeed!

http://forums.ubi.com/images/smilies/11.gif

Noticed the threads on the bolts in the crankcase are left hand threaded - is this correct or is your render mirror imaged?

KIMURA
04-05-2007, 11:58 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Redwulf 32 - Nis:
Noticed the threads on the bolts in the crankcase are left hand threaded - is this correct or is your render mirror imaged? </div></BLOCKQUOTE>

oooppss, I'll correct that, thanks.

JR_Greenhorn
04-05-2007, 12:19 PM
While I can't help you with your problem directly, have you checked the book R-2800: Pratt & Whitney's Dependable Masterpiece by Graham White? I haven't read it (it's on my books-to-buy list), but I would suspect the info you're looking for would be covered in it.

It looks like you'll need to do the cam rings next, but is the outer set of planet gears for the prop reduction or supercharger drive? I'm assuming this is the back of the engine and those are the supercharger drive planetaries.


What CAD package are you using? Some of the details are reminiscent of SolidWorks, but I suspect it's something else.

Also, are your gear teeth cut with involute profiles, or are they a simpler straight-geometry cut? The edges look simple, but some of the shaded faces look like they could be involute profiles.


How does your workstation like all of those fins and gear teeth?

Daiichidoku
04-05-2007, 12:45 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by KIMURA:
http://mypage.bluewin.ch/a-z/kimura-hei/B1.jpg
</div></BLOCKQUOTE>


this is EXACTLY the condition in which Oleg modelled the R-2800s to run in game

mystery solved

KIMURA
04-05-2007, 05:33 PM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JR_Greenhorn:
While I can't help you with your problem directly, have you checked the book R-2800: Pratt & Whitney's Dependable Masterpiece by Graham White? I haven't read it (it's on my books-to-buy list), but I would suspect the info you're looking for would be covered in it.

It looks like you'll need to do the cam rings next, but is the outer set of planet gears for the prop reduction or supercharger drive? I'm assuming this is the back of the engine and those are the supercharger drive planetaries.


What CAD package are you using? Some of the details are reminiscent of SolidWorks, but I suspect it's something else.

Also, are your gear teeth cut with involute profiles, or are they a simpler straight-geometry cut? The edges look simple, but some of the shaded faces look like they could be involute profiles.
How does your workstation like all of those fins and gear teeth? </div></BLOCKQUOTE>

Hi Greenhorm
I'm using Solid Edge(you'll surely know that). The gear teeth are simplified involute profile without any radius on the tooth ground, just of the reason for not blowing up file size and CPU capacity. You surely can imagine the effect if all cylinders are shown with their cooling rips and all the gears would be modelled and shown. http://forums.ubi.com/images/smilies/16x16_smiley-indifferent.gif

Here are some couple of pics that shows some difference to the Graham book. The Graham book don't excactly show the gear situation between the round yellow seperating plate and the planetary cage and how the crank shaft drives the planetary gears. http://forums.ubi.com/images/smilies/16x16_smiley-surprised.gif

http://mypage.bluewin.ch/a-z/kimura-hei/pw_r280020.jpg

http://mypage.bluewin.ch/a-z/kimura-hei/04-POF-PrattWhitneyR2800.jpg


Also does that link shows some differences to the real situation.
R-2800 CAD (http://www.nomeking.com/animations/radials/index.html)

JR_Greenhorn
04-05-2007, 10:25 PM
I think I'm getting this figured out. That first cutaway photo is really telling.

I'll take a stab at this then. What's confusing me the most is the stepped planet gears, and whether there's a single sun gear driving them via one "step" of the planets, or if there is somehow two sun gears in there, one driving and the other not.

If there is just a single sun gear, which must be driven by the crankshaft itself, power would be fed to the wider, smaller diameter portion of the stepped planet gears. The narrower, larger diameter portion of the stepped planet gears runs on the stationary (fixed to the housing) outer ring gear. Because the sun gear is driving and the outer ring gear is stationary, the rotation of the planets around the sun causes the planets' carrier to rotate. If my assumptions are correct, the propeller and the engine should rotate in in the same direction.
Can you verify that?

There are a few other things I'm trying to figure out based on what I'm seeing in that first cutaway photo. However, I can't go any further without some numbers. Do you have accurate tooth counts for each of the gears in the gearset? The spec'd overall reduction for that same gearset would be helpful as well. With those numbers, I can confirm what's going on and also satisfy some of my curiosities regarding the widths of those gears.

The-Pizza-Man
04-06-2007, 12:59 AM
I thought that looked like solidedge, what version ? 19? I hope you've been contraining and dimensioning your parts properly. I use AutoCAD at work and Solidedge at uni, I much prefer Solidedge.

KIMURA
04-06-2007, 06:10 AM
Greenhorn
The thing that's irritates me is also the coupling of the propeller shaft to the crankshaft. Both must be disconnect from each other. Here the situation out of the Graham White book(its also backed up by a 2nd source.) The propeller shaft is highlighted in yellow and and at its end there's a cone which is partly inserted into the crank shaft. So out of that situation my impression is that crank shaft and prop shaft turn the same direction, because not to double bearing speed. I just ordered a R-2800-8 mechanical manual @ Ebay for help.

http://mypage.bluewin.ch/a-z/kimura-hei/hub.jpg


Here the situation outside the R-2800 main housing. Flutes on the crank shaft connecting a gear that drives 2 douple packs of gears. The wider gear seems to drive the rocker ring, whereas the smaller one drives a inner toothed gear that drives one of the fixed gears of the sun U mentioned.
http://mypage.bluewin.ch/a-z/kimura-hei/hub2.jpg

KIMURA
04-06-2007, 06:17 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by The-Pizza-Man:
I thought that looked like solidedge, what version ? 19? I hope you've been contraining and dimensioning your parts properly. I use AutoCAD at work and Solidedge at uni, I much prefer Solidedge. </div></BLOCKQUOTE>

You can order Solid Edge V19 ACADEMIC for free at a distibutor near you. http://forums.ubi.com/images/smilies/winky.gif

JR_Greenhorn
04-06-2007, 10:31 AM
The coned prop shaft sheds some light on things. I couldn't figure out why the smaller diameter portion of the planet gears would be so wide if they were doing what I assumed they were. However, now it looks more like they are the final transfer of power from the planetary gearset to the prop shaft, which makes sense because the associated loads would require wide gears.

If that is the case, then not only must the big yellow carrier rotate, but the actual propshaft must rotate inside the carrier. It's hard to tell from the cutaway photos, but from what you've seen, does it look like there's enough bearings at the very front of the housing for this to be the case?



Regarding the gears you describe as "2 douple packs of gears" outside the main housing/crankcase: I don't think these gears have any connection to the propeller reduction gearset. I think they are only for the coutnerbalancers. If you look at the "Second Order Counterbalances" screenshot in the link to the other CAD R-2800 you posted, you can see the back side of one of the couterbalances on the right side of the screenshot. Here, you can see the material removed to make the offset weight of the counterbalance. These drives are, like you said, with a gear splined to the crankshaft that drives the 2 double gears, which drives the counterbalance itself that spins freely on the crankshaft. As the link states, these spin at twice crankshaft speed.

I also don't think those counterbalance gears drive the cam rings. I think in the first cutaway photo you posted, you can see part of one of the cam drive gears through the hole in the upper right area of that yellow separating plate. Looking at the second cutaway photo, the cam drives seem to each be in their own compartment, separated from the prop reduction housing in the front, the supercharger drive in the rear, and both are separated from the crankcase. I'm sure all of that partitioning is for oil control.



Back to the prop reduction itself, I noticed a few other interesting things in the link to that other CAD R-2800. If you look through the holes in his red rotating carrier, you can see a red sun gear of some sort inside. The holes in that gear nearly line up with the holes in the carrier, but you can see some of its teeth through the upper- and lower-most carrier holes. This sun gear appears to be running on the smaller diameter portion of the stepped planet gears, but it's not clear what else is going on behind that sun gear and the carrier. Additionally, in his caption he discusses "15 pinions." If there are 6 double-gear planets, that would be 12 pinions, plus that sun gear you can just barely see would be 13, leaving two "pinions" unaccounted for. If there are 7 planets, that would be 14 plus that sun gear, which would be 15, meaning there aren't any other gears besides the ring gear. It looks to me like 6 planets, not 7, is correct, so where are the other two "pinion" gears?


I'm starting to think that there must be a sun gear feeding power from the crankshaft to the larger diameter portion of the planet gears. That still doesn't explain where the "15th pinion" would be.


I think it's obvious that this all intrigues me. Epicyclic gearing is just so mechanically beautiful. I want to look further into all of this, but I have to leave town this weekend. If you get it figured out before then, you'll have to let me know.



I'm still wondering about those tooth counts. Did you model your gears with the exact tooth counts of the actual gears, or are they a "best guess" that look the part? Do you have any pictures that show any of the gears clearly enough to count the teeth?

KIMURA
04-07-2007, 05:07 AM
Check PM Greenhorn