dcavy Posted November 14, 2011 Share Posted November 14, 2011 does anyone know where i can find an article on how to create a gearbox for motorized twin opposing props. I could swear at one time someone had an article on a tu-95 with pics but despite looking on googe all i coud find was RC stuff. any help would be great. Quote Link to post Share on other sites
Flankerman Posted November 14, 2011 Share Posted November 14, 2011 A friend of mine did some for my Bristol Brabazon - but it only worked because there was enough room in the wing leading edge to have the motor mounted transversly..... The arrangement was very simple - but I doubt you could do it in a narrow Tu-95-style nacelle..... It also isn't very smooth and runs far too fast to be realistic..... .... but it does work..... Ken Quote Link to post Share on other sites
Two Mikes Posted November 14, 2011 Share Posted November 14, 2011 does anyone know where i can find an article on how to create a gearbox for motorized twin opposing props. I could swear at one time someone had an article on a tu-95 with pics but despite looking on googe all i coud find was RC stuff. any help would be great. Someone did have it at the 2010 IPMS Nationals here in Phoenix. It had a 1/72 F-106 "flying" off its wing. I cannot remember who built it but you may be able to google it. Quote Link to post Share on other sites
Lucien Harpress Posted November 14, 2011 Share Posted November 14, 2011 Let me do some digging. I made a (mostly) working gearbox like this a while back, and was able to get from the Tu-95 guys the same gears they used. I'll get back to you tonight with pics and links. Be warned, though- it is a MAJOR PITA, even when things to perfectly. Which they don't. Ever. But, still, let me dig up what I got. http://s362974870.onlinehome.us/forums/air/index.php?showtopic=225665 (My previous thread, including this video:) http://smg.photobucket.com/albums/v296/LHprs/?action=view¤t=MVI_2131.mp4 Quote Link to post Share on other sites
dcavy Posted November 14, 2011 Author Share Posted November 14, 2011 fortunately i would be looking at building one only for an xfy-1 thought this would be a pretty sweet touch. Quote Link to post Share on other sites
Fiddler Posted November 16, 2011 Share Posted November 16, 2011 (edited) A friend of mine did some for my Bristol Brabazon - but it only worked because there was enough room in the wing leading edge to have the motor mounted transversly..... The arrangement was very simple - but I doubt you could do it in a narrow Tu-95-style nacelle..... Maybe the engine could be positioned a bit more aft where the wing is at it's thickest. Or you could try and fix it in the fuselage, with a driveshaft running down the wing to the gearboxes. It also isn't very smooth and runs far too fast to be realistic..... .... but it does work..... I don't know on what power it runs, but if the engine is running on DC power, you can install some electronics to lower the rpm to a more realistic level. But not that I'm saying your Brabazon is a crappy build. In contrary, it's looking stunning from what I can see, as do all your models. To bad we only see the engines :) Greetings! Edited November 16, 2011 by Fiddler Quote Link to post Share on other sites
2qwik4u Posted November 16, 2011 Share Posted November 16, 2011 Didn't the Trumpeter 1/48 Wyvern have a gearbox in it for contrarotating props? Quote Link to post Share on other sites
Lucien Harpress Posted November 16, 2011 Share Posted November 16, 2011 (edited) Sorry for the delay. Two retail jobs + Thanksgiving = NO free time. BUT- I've got something. The gears I used came from here: https://sdp-si.com/ The particular part number is A 1M 4MYZ 05. That's about as small as you want to go with gears, and should fit fine in an XFY-1 (what you're building, correct?) As for a motor, I'd recommend a geared one, like these: http://www.robotcombat.com/products/motors_geared.html (Just an example from a 5 second Google search- never used em, so I can't speak for quality of this particular website, but you get the idea) The thing with making your own gearbox is that you will NOT get it perfect. Unless you have a full machine shop setup, the best you can hope for is to get it close. Geared motors offer two benefits- first, they slow down the motor speed without losing torque, unlike what would happen when you'd slow it down electrically. Second, you'll actually GAIN torque using them, which you WILL NEED, even in the best case scenario. There's a LOT of places for friction to build up in these things, and you'll need all the help you can get to power through any minute building inaccuracies. Next, if you're running a 1.5v motor, the smallest battery you'll be able to get away with is a AAA, MAYBE a AAAA if you can find 'em. Those button batteries just don't have enough juice. Finally, I personally would glue down the gearbox nice and solid, but mount the motor in a way so it can "float" (a blob of sticky tac works nicely). Then run the motor, gently adjusting it until you get the whole mess to run smoothly. Then, do NOT glue it in rigid- continue to allow it to "find" it's own seat. (I made this mistake on the XP-56- ran fine when I put it in, but minor changes that happened when I glued it all together knocked it out of alignment and made it run rougher once it was all closed up.) This way, it should (usually) help keep itself aligned as you run it. That's all I got. I wish you the best of luck, and I'll keep an eye out for any progress. Hope this helps. Just lemmie know if you've got any questions. Edited November 16, 2011 by Lucien Harpress Quote Link to post Share on other sites
Griffin Posted November 18, 2011 Share Posted November 18, 2011 Hi, Finally, I personally would glue down the gearbox nice and solid, but mount the motor in a way so it can "float" (a blob of sticky tac works nicely). Then run the motor, gently adjusting it until you get the whole mess to run smoothly. Then, do NOT glue it in rigid- continue to allow it to "find" it's own seat. (I made this mistake on the XP-56- ran fine when I put it in, but minor changes that happened when I glued it all together knocked it out of alignment and made it run rougher once it was all closed up.) This way, it should (usually) help keep itself aligned as you run it. You can also try with a small spring in between the engine shaft and the gearbox assembly. I experienced it successfully a long time ago, with an engine set at en angle and even lower... it runned perfectly smooth ( and because the spring is somewhat soft, the blades "shakes" a little on power start and cut, just like 1/1 scale props does... :)) Should work as well with a gearbox, minus the prop shake effect... Quote Link to post Share on other sites
Lucien Harpress Posted November 19, 2011 Share Posted November 19, 2011 Hm... I always used wire insulation for my "U-joint", but the spring ain't a bad idea.... gets me thinkin'.... Quote Link to post Share on other sites
Netz Posted November 19, 2011 Share Posted November 19, 2011 contra rotating Quote Link to post Share on other sites
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