Angle Drive Gear Reduction Ratio?

[LordFly]

Or better yet go back to your original idea of a complex transmission that provides the same ratio. That might actually work... if you use a planetary gear set the forces would be divided among all those teeth working together. That's a cool idea

That actually was my original thinking, spreading the load across extra teeth. It's going to be overly complex to be such a low ratio. Do-able, but complex. The only problem is that it won't have a 90° turn...

[Nicholas R]

Even if you're not an engineer your thinking is much better than that of the engineer who designed this setup. Bevel gears would be a much better choice in this case as the forces are now just huge. Bevel gears with angled teeth would be quiet and would last the life of the car. No wonder those angle drives keep failing.

I don't think plastic gears from a 3D printer would last more than 9 turns let alone kilometers. The forces are really great in this setup even without the cables and two counters. Try building one using bevel gears with the same ratio and they might last for a few kms. Or better yet go back to your original idea of a complex transmission that provides the same ratio. That might actually work... if you use a planetary gear set the forces would be divided among all those teeth working together. That's a cool idea

Helical gear teeth distribute the load better across a larger tooth (even multiple teeth depending on the cut) than straight cut or bevel gears. In addition straight and bevel gears have very high transverse loads because the gears are always trying to push each other apart. Helical gears instead have much more axial loading, which is much easier to manage, and won't cause the teeth to strip anywhere near as easily. They also operate much quieter because the teeth are sliding. These are the same reasons why every car differential uses curved hypoid gears, not beveled gears (differentials also have other reasons for using hypoid gears too but these are some of them).

EDIT: I'm not saying that a planetary or bevel gear design wouldn't work, I'm just saying that these were most likely the things the engineer that designed this was thinking about. Plus, for production, rolling gears like this would be very cost effective. Also I've never heard of the teeth of an angle drive being the part that fails. I've always seen it being the rod that goes to the wheel hub.

[LordFly]

A planetary gear system can have helical gears as well https://d2t1xqejof9utc.cloudfront.ne...9cb/medium.png And so could a bevel system, although at that point you basically have a hypoid anyways. I didn't want to get to technical on the types of gears when I was just looking for the ratio The original design could have been better if they'd tapered the center of the output gear, instead of basically just making a worm gear. It's not spreading the load well at all, which is why it's wearing so bad right in the middle. I might try a few things

[Shep]

You know what LordFly? Go for it. Seriously, take your 3D printer and make some gear systems. When you think about it, plastic has such a low durability in automotive use, it'll let you see right away what systems would last and what systems wouldn't based on simple testing with a drill or some such. Plastic is so inexpensive nowadays, you can easily make every single gear system known to man that would be even halfway suitable and try them all out. Multiple times even. Based on how they wear, break, and how long they last, I'm sure you'll gather a huge, HUGE amount of useful information that may even lead you to design a gear type that would be even better suited for the task

I for one am rooting for you, and sincerely hope that this will lead to better things. Who knows, maybe you'll discover a system that'll work better than what anyone else has tried so far! Obviously the end result would be metal, but this is the true heart of "Rapid Prototyping" at its finest -- try out a bunch of prototypes and see what works best. Looks like 3D printing has finally come full-circle in the DeLorean world, in a very good way! Best of luck to you, and keep us posted on the results!

[chris williams]

According to the calculation the speedometer and the odometer is 12.5% slower when connected directly to the wheel.

probably correct I was looking at the speedo and GPS at the same time so would vary a little, either way it reads slow so people need to watch out for this with all the speed traps/cameras around.
Chris

[LordFly]

You know what LordFly? Go for it. Seriously, take your 3D printer and make some gear systems. When you think about it, plastic has such a low durability in automotive use, it'll let you see right away what systems would last and what systems wouldn't based on simple testing with a drill or some such. Plastic is so inexpensive nowadays, you can easily make every single gear system known to man that would be even halfway suitable and try them all out. Multiple times even. Based on how they wear, break, and how long they last, I'm sure you'll gather a huge, HUGE amount of useful information that may even lead you to design a gear type that would be even better suited for the task

I for one am rooting for you, and sincerely hope that this will lead to better things. Who knows, maybe you'll discover a system that'll work better than what anyone else has tried so far! Obviously the end result would be metal, but this is the true heart of "Rapid Prototyping" at its finest -- try out a bunch of prototypes and see what works best. Looks like 3D printing has finally come full-circle in the DeLorean world, in a very good way! Best of luck to you, and keep us posted on the results!

Yup, absolutely right. The plastic is next to worthless. I'm in no way worried about wasting it. And should something work really well, I can always have shapeways.com print it in metal (they even have stainless ). The biggest problem right now is that when you get right down to it, the math behind drawing a proper involute gear is pretty damn complicated! And SolidWorks doesn't seem to have an internal helical gear for my planetary setup in their drag and drop menu. Also, they seem to cheat a little on their drag and drop gears. I don't think their involutes are quite right, because they don't seem to mesh like they should. And I'm kinda picky about stuff like that.

[Nicholas R]

A planetary gear system can have helical gears as well https://d2t1xqejof9utc.cloudfront.ne...9cb/medium.png And so could a bevel system, although at that point you basically have a hypoid anyways. I didn't want to get to technical on the types of gears when I was just looking for the ratio The original design could have been better if they'd tapered the center of the output gear, instead of basically just making a worm gear. It's not spreading the load well at all, which is why it's wearing so bad right in the middle. I might try a few things

Helical gears allow you to distribute the load over a larger tooth face; even multiple teeth depending on the specs. You wouldn't end up with hypoid gears; (properly machined) helical gears are still involute gears.

I still disagree with trading axial loads for transverse loads because that's how you strip gear teeth. I believe the wear you see now would be small compared to what you'd see after the equivalent number of miles with straight cut beveled gears. We can just agree to disagree. I certainly don't want this to stop you from experimenting. I'd love to see what you come up with

[Nicholas R]

By the way, given the size if your parts and teeth, is the printing resolution going to be fine enough for you to need to detail your tooth profiles to a true involute?

[Shep]

SolidWorks doesn't seem to have an internal helical gear for my planetary setup in their drag and drop menu.

Have you thought about using a different program for the gear part of it? Think of it as using a claw hammer as a bottle opener. It'll work if you do it right, but it's not really meant for that. Different tools for different jobs, although an attachment for the claw might work better.

Tried a Google search for "3d gear generator", and came across a few links of interest:
http://woodgears.ca/gear/index.html
http://discourse.mcneel.com/t/a-new-...generator/4923
http://www.thingiverse.com/thing:8077

That last one uses SolidWorks, hence the "attachment" metaphor. Maybe it'll work after all

[LordFly]

By the way, given the size if your parts and teeth, is the printing resolution going to be fine enough for you to need to detail your tooth profiles to a true involute?

Hard to say. X and Y resolution is approximately 0.015mm, but Z can only reliably go down to about 0.1mm, so tiny helical gears may have minor issues, but they should be pretty good. I was thinking of scaling up to see how it works out first.

I printed some gears for a motorized projector screen I built about 6 months ago. It's got a fair bit of load on it and last time I looked it showed no signs of wear. But they were moderately large teeth.

Ultimately I won't know until I try it. I might try first just with some basic straight gears, or bevels or something, just to start somewhere and see how much room I have to play with.