[HELP] Transmission Problems

[Sir_Samsalot]

Hello again. Many of you will probably remember me from a post I made about a week and a half ago asking for help for a pulley system of my automated warehouse machine. Well, since then, I've attached four separate pulleys to the main transporter and I've been hard at work designing the entire pulley mechanism / horizontal transporter. Allow me to introduce you to this monster:

As you can see, I have a serious overengineering problem.

Anyway, the device features a total of 8 separate pulleys, arranged in 4 groups of 2. Things were going perfectly well until I realized that my 1:72 gear ratio (I've been trying to allow the system as much torque as possible) is, as you might guess, incredibly slow. I then got the idea for a 2-speed transmission, one at 1:72 and the other at ~1:14, which would be controlled by another PF motor to keep the system automated. Here are a few pictures of the transmission area:

This is a bottom view. The moving section is the two white 9-stud connectors and everything attached to them.

This picture shows the way that I intend to control the transmission with a motor (The PF motor will be put in the spot where the black gear is).

Here is a top-down picture that shows how the moving part connects to the gear box. You can barely see the two white connectors buried beneath everything else.

So this is all working perfectly well, except for one major flaw. Here's the problem area in question:

The problem lies with the two 24-tooth gears that are connected to the worm gears. Both 24-tooths unfortunately lie on the only two moving axles in my transmission, and both gears have no room to move left or right without sliding on the axle. Because of this, the only way to change speeds means pushing hard enough on the axles themselves to slide the two problem gears back and forth. This requires too much force for my transmission to handle using the motor setup, and the whole setup is extremely awkward and clumsy even if I manually push both axles.

Even worse, the only way I can see to fix this flaw is to redesign most of the gearbox. However, since every section of the machine is packed together and thus intricately connected, I would have to tear most of the setup apart just to gain access to the gearbox, and even then I don't have very much wiggle room because of the lack of space. Do any of you have any better suggestions, and if I do have to redesign the gearbox, do you have any suggestions on the best design I could use to avoid this mess again? Any ideas are greatly appreciated.

[MrNumbskull13]

I would start over again, maybe not completely, just keep the parts that work well. Try planning ahead, you could design it on paper, then start building. Also, I would suggest you build modular so that if one part fails you can detach and rebuild it much easier, it would also make trouble shooting a lot easier.

Good luck!

[Zerobricks]

Sorry, but it looks so messy and random... Also using worm gears and Xl motors is bound to break something.

[Jullian_pdx]

The crown gears are not going to be able to handle much torque especially meshed to a type 1 - 8 tooth gear

[Milan]

Definitely start over again. I usually make 5-10 version of the sam thing until fully satisfied.

[dhc6twinotter]

Interesting project. It looks like you are forcing an axle to slide within a 24t gear, which is no beuno. Here are 4 different options you could try:

1) Move the blue beams to 3 studs apart from each other. Use two 24t gears on the sliding axle. When the axle slides, one 24t will disengage from the worm gear, and the other 24t will engage. You may have a brief moment where nothing is engaged, which may not be suitable for your application (I'm not sure).

2) Use the new red 8t gear found in the crane set. This gear slides on axles, and you can use this instead of the 24t gear. You would have to lower your motor and worm gears by 1 stud. However, I'm not sure the red 8t gear would handle the torque of an XL motor.

3) Axles slide smoothly through worm gears. You can place your worm gear and axle parallel to your sliding axle, but this would require a 90 degree turn in your driveline somewhere between your worm gear and gearbox. Let the axle slide inside your worm gear. Since you are using an XL motor, use something like the 5x7 frames to properly brace the 90 degree driveline turn. Use double bevel gears here as well.

4) Ditch the crash box style gearbox you have here and switch to a more traditional LEGO gearbox using clutch gears and driving rings.

Option 3 or 4 is probably best.

Are you using two different speeds so that the lifting the hook can be slower than the lowering?

Edited June 7, 2014 by dhc6twinotter

[Sir_Samsalot]

Thank you for all of the replies. I figured I would end up having to redesign the majority of it (lesson learned: lack of planning = huge mess).

Also, to dhc6twinotter, I am using two different speeds because the mechanism will be lifting a large variety of weights, from very heavy to relatively light (If you can call lifting a Mindstorms brick and a few motors light), so I wanted to try and replace some of the unnecessary torque with a bit of speed (for efficiency's sake) for the lighter loads.

Edit: Since my application for the transmission will not involve changing speeds under excessive load, I'll probably work with your 1st option. Thank you for all of the suggestions.

Edited June 7, 2014 by Sir_Samsalot