RFQ 2 ea. main bevel gear and matching pinion bevel gear - Page 3
Close
Login to Your Account
Page 3 of 4 FirstFirst 1234 LastLast
Results 41 to 60 of 62
  1. #41
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by Milland View Post
    ...For the main gear, a tough, hard plastic like PEEK might work for you, ideally with a fill material like glass or carbon fiber (but you'd NEED hard metal pinions with a fill).

    StackPath

    Replacing Metal with PEEK Polymers to Improve Gear Reliability, Performance and Efficiency

    ...
    I'll check out PEEK polymers. I was thinking of making the main bevel gear out of glass-filled nylon, but don't know if/how it could be machined.

    The most popular propellers for alcohol/castor oil fuel model aircraft engines are made of glass-filled nylon by Master Airscrew but they're injection molded. Cost prohibitive until I win the lottery.

    Classic Series | Master Airscrew

  2. #42
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    21,348
    Post Thanks / Like

    Default

    Quote Originally Posted by saucerdesigner View Post
    I'm not an engineer either and very inexperienced at machining, obviously, and not sure I understand how a reduction gearbox would help in my case. The main gear diameter and RPM cannot be changed as the lift to be produced is predicated on those values. The main gear is a ring bevel gear supported by bearings at multiple points around the periphery.
    Thanks for the suggestions though.
    You missed the part about "lower tooth speed will help it live", so you doo the reduction in stages, not all at once, with a planetary gear, not all at the bevel.

    You really, really need to seek out a gear expert.

  3. #43
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by digger doug View Post
    snip - You really, really need to seek out a gear expert.
    Agreed. I'll seek out a gear expert before requesting a quote again. Suggestions on a gear expert are welcome.
    The main gear has to turn at 6K RPM (at full throttle). There is no option for further reduction. Are you suggesting I use the planetary reduction to reduce from 5 to 1 in stages (adds weight, complexity and losses)? Forgive me but I don't see how that will lower the tooth speed of the main bevel gear.
    Last edited by saucerdesigner; 04-16-2021 at 08:09 PM.

  4. #44
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    12,680
    Post Thanks / Like
    Likes (Given)
    2894
    Likes (Received)
    8787

    Default

    Quote Originally Posted by saucerdesigner View Post
    Agreed. I'll seek a gear expert out before requesting a quote again. Suggestions on a gear expert are welcome.
    The main gear has to turn at 6K RPM (at full throttle). There is no option for further reduction. Are you suggesting I use the planetary reduction to reduce from 5 to 1 in stages (adds weight, complexity and losses)? Forgive me but I don't see how that will lower the tooth speed of the main bevel gear.
    I think I'm with DD now, free advice on PM has sort of reached its limit.

    If you're set on a specific size and pitch of prop so you need that RPM at the blade, the idea of the staged reduction is so the surface speed at the final drive is reduced, with larger-section teeth to handle the loads and reduce deflection.

    So roughly a 2.5-1 reduction with the planetary box, then a 2-1 at the final drive to go from 30K to 6K. Remember, the worry expressed by others was about the surface speed of the meshing teeth, with a smaller main gear (from 12"+ to ~4") you cut that speed at the teeth, while still maintaining the desired 6K RPM.

  5. #45
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    7,509
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3660

    Default

    Quote Originally Posted by Milland View Post
    with a smaller main gear (from 12"+ to ~4") you cut that speed at the teeth, while still maintaining the desired 6K RPM.
    Someone actually sells off-the-shelf ground tooth spiral bevels in 1:1, 2:1, and I think 3:1 ratios. Can't remember who but they are out there.

    You also need to know what the load is before you go off half-cocked choosing materials ?

  6. #46
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    12,680
    Post Thanks / Like
    Likes (Given)
    2894
    Likes (Received)
    8787

    Default

    Quote Originally Posted by EmanuelGoldstein View Post
    Someone actually sells off-the-shelf ground tooth spiral bevels in 1:1, 2:1, and I think 3:1 ratios. Can't remember who but they are out there.
    But, but, but - don't you want the non-repeating tooth mesh?

    You also need to know what the load is before you go off half-cocked choosing materials ?
    Last time I went off full-cocked, the ladies all fainted, the cattle got pregnant, and storks went on strike due to overwork.

  7. #47
    Join Date
    Oct 2005
    Country
    UNITED STATES
    State/Province
    Pennsylvania
    Posts
    21,348
    Post Thanks / Like

    Default

    Quote Originally Posted by saucerdesigner View Post
    Agreed. I'll seek a gear expert out before requesting a quote again. Suggestions on a gear expert are welcome.
    The main gear has to turn at 6K RPM (at full throttle). There is no option for further reduction. Are you suggesting I use the planetary reduction to reduce from 5 to 1 in stages (adds weight, complexity and losses)? Forgive me but I don't see how that will lower the tooth speed of the main bevel gear.
    Your still not understanding. It's not the speed of the teeth, it's the mesh, you know the "rolling action" that is from properly made gears. And bevel gears are compromise in that department, hence the speed limits.

    We can only devote so much to teaching you.

    There are many books on gear design.

  8. #48
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    7,509
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3660

    Default

    Quote Originally Posted by Milland View Post
    But, but, but - don't you want the non-repeating tooth mesh?
    Not particularly. Especially not with ground, carburized teeth. Unless this thing weighs 3 lbs total, not a chance in hell his aluminum/delrin gearset will hold up.

  9. #49
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    If my math is correct the load on the main gear at design point is estimated at:
    hp:1.7
    torque [lb force-ft]:1.5
    power absorbed [Watt]:1282.4

  10. #50
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by Milland View Post
    I think I'm with DD now, free advice on PM has sort of reached its limit.

    If you're set on a specific size and pitch of prop so you need that RPM at the blade, the idea of the staged reduction is so the surface speed at the final drive is reduced, with larger-section teeth to handle the loads and reduce deflection.

    So roughly a 2.5-1 reduction with the planetary box, then a 2-1 at the final drive to go from 30K to 6K. Remember, the worry expressed by others was about the surface speed of the meshing teeth, with a smaller main gear (from 12"+ to ~4") you cut that speed at the teeth, while still maintaining the desired 6K RPM.
    Thank you for the explanation. So if I understand, since the main gear has to stay at 12"+, after the 2.5-1 reduction the mating pinion will be 6"+.
    Very much appreciated. Sorry to be such a pain.
    SD

  11. #51
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    12,680
    Post Thanks / Like
    Likes (Given)
    2894
    Likes (Received)
    8787

    Default

    Are you saying that the prop is within the main gear? And you have to drive the periphery by design?

    Good heavens, you do like a challenge...

  12. Likes saucerdesigner liked this post
  13. #52
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    7,509
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3660

    Default

    Quote Originally Posted by saucerdesigner View Post
    So if I understand, since the main gear has to stay at 12"+,
    I think you missed his point. If you put, say, a 2:1 reduction ahead of the pinion, then your main gear diameter will drop to 6". This is desirable because the pitch line velocity goes up as the square of the radius. (Same as surface speed.) 18,000 fpm is more than a little too fast.

    hp:1.7
    torque [lb force-ft]:1.5
    power absorbed [Watt]:1282.4
    A couple of basic basics : a good set of parallel axis gears can be up to 98% efficient. That means 2% of the power transmitted goes up in heat. You ain't gonna be nowhere near 2%, better figure 5% at least and if you want to be honest, a lot more than that. Your delrin teeth are not going to like 100 watts of heat being continuously pumped into them. If you really transmit 1.7 hp then you best add another 10% for losses, then double that number at least for a safety factor. Then you need to do something about lubrication and heat removal. This isn't a pond yacht, if you lose the rotor drive then down will come baby, cradle and all.

  14. Likes saucerdesigner liked this post
  15. #53
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by EmanuelGoldstein View Post
    This isn't a pond yacht, if you lose the rotor drive then down will come baby, cradle and all.
    Agreed.
    I also agree with DD on consulting a gear expert. If anyone could recommend one I'll gladly give them a shout.
    Again, the main gear OD has to stay at 12"+. I don't know how to put it any more simply or clearly.
    I had considered parallel axis gears at first but chose the bevel gear configuration to save lateral size and resulting increase in weight, as the motor, and now the reduction box and pinion cannot be internal to a parallel axis main gear...they would have to be external.
    The teeth don't have to be Delrin. I'm studying the other materials suggested by Milland.
    Thanks.
    Last edited by saucerdesigner; 04-17-2021 at 10:23 AM.

  16. #54
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by Milland View Post
    Good heavens, you do like a challenge...
    Yessir, this challenge has pulled me through the devastation of loosing a 25+ year career as a professional pilot and flight instructor.
    In 1995 I had my chest crushed between two 40' joints of 13&3/8" dia. well casing, @ 54 lb per foot; on a pipe rack in a shop where I was supposed to be learning to program the CNC lathes that cut new threads on the used pipe. The stroke which resulted ended my eligibility for an FAA Airman's medical.
    I was learning to write code on the Mac in the Pascal programming language to design the main propulsion component for this project before I went to work for them as their corporate pilot on the condition that I learn to program the CNC lathes.
    The shop foreman who was supposed to be teaching me how to program the Fanuc controllers had me doing grunt work on the pipe rack one day when the injury occurred. I had to switch from the Mac to Windows machines to get work as an IT contractor after learning how to walk again.
    Thankfully, a few years ago I discovered Rhino 3D CAD and with it the Python programming language which is a very easy programming language to learn and use.
    The result is this gear I'm trying to have made.

  17. #55
    Join Date
    Jul 2006
    Location
    Hillsboro, New Hampshire
    Posts
    12,680
    Post Thanks / Like
    Likes (Given)
    2894
    Likes (Received)
    8787

    Default

    Well, that was a rough welcome to the world of machining. Incredibly negligent of the foreman to put you in that situation, I hope you got some decent settlement from that accident (not that money can give back your health).

  18. #56
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    It wasn't his fault. Incredibly reckless of me, truth be told.
    At the outset he pointed out the 1/2 x 1/2 x 4 inch piece of angle iron at my feet to put on the rack uphill from me to stop the next joint from hitting me if need be. I thought I could get the joint that was stuck at my station rolling down the rack before the operator uphill could eject the next joint and send it rolling my way. I had earplugs in with my chest against the motionless joint tying to get it rolling and with all the steel banging in the shop couldn't hear anyone yelling at me to duck. At the last second I turned my head to see it coming but it was too late. I flinched and braced for the impact. It felt like I'd stopped a Buick. Left side went weak after I crawled out from under the pipe. The result was total occlusion of the right internal carotid artery.
    My impairment rating was only 15%, so the settlement didn't amount to much.
    I'll never forget what he said when I was introduced to him on my first day on the job. He was a former Air Traffic Controller who was among those fired by Ronald Reagan when they went on strike: "A pilot! I like telling pilots what to do. Welcome to hell."

  19. #57
    Join Date
    Apr 2018
    Country
    UNITED STATES MINOR OUTLYING ISLANDS
    Posts
    7,509
    Post Thanks / Like
    Likes (Given)
    0
    Likes (Received)
    3660

    Default

    Quote Originally Posted by saucerdesigner View Post
    Again, the main gear OD has to stay at 12"+.
    Then you're in deep shit, because that's way too fast. End of story.

  20. #58
    Join Date
    Mar 2017
    Country
    LATVIA
    Posts
    782
    Post Thanks / Like
    Likes (Given)
    216
    Likes (Received)
    454

    Default

    has OP given a thought of using belt drive instead of gears? if the right angle input is a necessity, perhaps that could be done before driving the main shaft, twisting the belt might be an option also

  21. #59
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by jz79 View Post
    has OP given a thought of using belt drive instead of gears? if the right angle input is a necessity, perhaps that could be done before driving the main shaft, twisting the belt might be an option also
    The right angle drive is history for all the reasons pointed out earlier by others.
    Yes, in the project's infancy I had considered timing belts and pulleys from Stock Drive Products but at these speeds and load I don't think the belts would last very long.

  22. #60
    Join Date
    Sep 2019
    Country
    UNITED STATES
    State/Province
    Texas
    Posts
    26
    Post Thanks / Like
    Likes (Given)
    10
    Likes (Received)
    2

    Default

    Quote Originally Posted by EmanuelGoldstein View Post
    End of story.
    As it should be. Mouth full of crow here. I apologize for the severe case of thick skull.
    The 12"+ dia. bevel gear supported at the periphery idea is in the trash where it belongs.
    Ever since I had pulled it out of the dark place in which I had it up-and-locked, I've had my head buried in Dudley's Gear Handbook and Doug Rogers' GearBakery, his port of Dr. Rainer Hessmer’s Involute Spur Gear Builder; in the process of designing a set of parallel-axis helical gears.
    In recognition of the grace and generosity of the investment of wisdom and time which all of you have shown, I humbly acknowledge that all of you who have offered suggestions and voiced your concerns have without doubt saved this project from certain failure and I will be forever grateful.
    Thank you.


Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •