4 minutes ago, I_Igor said:

I agree partially but you have to realize that machinery uses hydrostatic cvt, with one hydraulic pump and one hydromotor. As a professor I give you one homework - study how hydrostatic cvt works 

Will do. :)

Just now, cloud said:

Will do. :)

Just one hint - the only way to simulate hydraulic system is to put destilated water in pneumatic system. 

Just now, I_Igor said:

Just one hint - the only way to simulate hydraulic system is to put destilated water in pneumatic system. 

Yes, well I'm not emulating the hydrolics since Lego has no hydraulic system. I'm trying to emulate the functions of the various components at a high level. The real thing has hydrolic everything. I have Lego pneumatic or mechanical to choose from. As I have more mechanical parts than pneumatic I'm sticking to mechanical. Mechanical also arguably takes less space when trying to cram motors and a transmission into a 35x5x10 brick size for each shoe. If Lego had a pneumatic motor that fit, I'd be all over it... now that I said that a steam engine drive comes to mind... hmm mm.Thinking out loud,  I wonder if a cvt or pneumatic drive would be smaller. If the only concession is pneumatic instead of hydraulic then the cvt or at least a 2 speed automatic would still be required after the pneumatic drive segment, but it could have some crazy torque. I still think that a purely mechanical cvt is smallest and able to fit in the dimensions required for the model. If I just wanted it to go at various speeds I'd hook up a couple motors to tracks and use a train PF controller. 

Just to be clear are you pointing out that Lego has no hydraulic system or that the cvt doesn't work with high torque or that the cvt can't possibly replicate a hydrolic drive system accurately? 

39 minutes ago, cloud said:

Yes, well I'm not emulating the hydrolics since Lego has no hydraulic system. I'm trying to emulate the functions of the various components at a high level. The real thing has hydrolic everything. I have Lego pneumatic or mechanical to choose from. As I have more mechanical parts than pneumatic I'm sticking to mechanical. Mechanical also arguably takes less space when trying to cram motors and a transmission into a 35x5x10 brick size for each shoe. If Lego had a pneumatic motor that fit, I'd be all over it... now that I said that a steam engine drive comes to mind... hmm mm.Thinking out loud,  I wonder if a cvt or pneumatic drive would be smaller. If the only concession is pneumatic instead of hydraulic then the cvt or at least a 2 speed automatic would still be required after the pneumatic drive segment, but it could have some crazy torque. I still think that a purely mechanical cvt is smallest and able to fit in the dimensions required for the model. If I just wanted it to go at various speeds I'd hook up a couple motors to tracks and use a train PF controller. 

Just to be clear are you pointing out that Lego has no hydraulic system or that the cvt doesn't work with high torque or that the cvt can't possibly replicate a hydrolic drive system accurately? 

What I'm pointing my young friend is that with LEGO parts you can not make cvt that behaves as hydrostatic cvt, so as you mentioned you can not replicate it accurate. Another problem with pneumatic systen is that it uses air; so one simple lesson from school air can be compressed and liquid not. Speaking of compression there is sonething called LEGO pneumatic pump which when motorized can behave as pneumatic compressor and with air tank you have some possubilities. Give me some time to find a video dealing with pneumatic cvt valve control, so you can see principles (unfortinately it is to big for your model). In real world internal combustion engine (in most cases diesel engine) is used as hydraulic pump for hydraulic system.

58 minutes ago, cloud said:

Yes, well I'm not emulating the hydrolics since Lego has no hydraulic system. I'm trying to emulate the functions of the various components at a high level. The real thing has hydrolic everything. I have Lego pneumatic or mechanical to choose from. As I have more mechanical parts than pneumatic I'm sticking to mechanical. Mechanical also arguably takes less space when trying to cram motors and a transmission into a 35x5x10 brick size for each shoe. If Lego had a pneumatic motor that fit, I'd be all over it... now that I said that a steam engine drive comes to mind... hmm mm.Thinking out loud,  I wonder if a cvt or pneumatic drive would be smaller. If the only concession is pneumatic instead of hydraulic then the cvt or at least a 2 speed automatic would still be required after the pneumatic drive segment, but it could have some crazy torque. I still think that a purely mechanical cvt is smallest and able to fit in the dimensions required for the model. If I just wanted it to go at various speeds I'd hook up a couple motors to tracks and use a train PF controller. 

Just to be clear are you pointing out that Lego has no hydraulic system or that the cvt doesn't work with high torque or that the cvt can't possibly replicate a hydrolic drive system accurately? 

What I'm pointing my young friend is that with LEGO parts you can not make cvt that behaves as hydrostatic cvt, so as you mentioned you can not replicate it accurate. Another problem with pneumatic systen is that it uses air; so one simple lesson from school air can be compressed and liquid not. Speaking of compression there is sonething called LEGO pneumatic pump which when motorized can behave as pneumatic compressor and with air tank you have some possubilities. Give me some time to find a video dealing with pneumatic cvt valve control, so you can see principles (unfortinately it is to big for your model). In real world internal combustion engine (in most cases diesel engine) is used as hydraulic pump for hydraulic system.

In the meantime I have found out that solution about I was talking by @Mark Bellis can be found along with discussion here

My suggestion is to finish model first without cvt, and then you'll see what to do with it (under "it" I mean cvt). It would be real pitty that you run out of time because of cvt because it is a great project 

42 minutes ago, I_Igor said:

What I'm pointing my young friend is that with LEGO parts you can not make cvt that behaves as hydrostatic cvt, so as you mentioned you can not replicate it accurate. Another problem with pneumatic systen is that it uses air; so one simple lesson from school air can be compressed and liquid not. Speaking of compression there is sonething called LEGO pneumatic pump which when motorized can behave as pneumatic compressor and with air tank you have some possubilities. Give me some time to find a video dealing with pneumatic cvt valve control, so you can see principles (unfortinately it is to big for your model). In real world internal combustion engine (in most cases diesel engine) is used as hydraulic pump for hydraulic system.

I know all that. Not sure what age you take me to be, but it really makes no difference to the discussion. Lego is highly limited. That is the nature of the system. Thanks for pointing out that liquid doesn't get compressed. I was only pointing out that no hydrolic system exists in Lego, but when one takes the direct energy transfer of liquid in to account a purely mechanical representation is in some ways better than pneumatic. 

We all accept some lack of realism with Lego. I find it fun to try and make functions that have semblance to the real thing even if it is something as hard to compare as diesel/hydraulic to electric/electro-mechanical. 

8 hours ago, cloud said:

I know all that. Not sure what age you take me to be, but it really makes no difference to the discussion. Lego is highly limited. That is the nature of the system. Thanks for pointing out that liquid doesn't get compressed. I was only pointing out that no hydrolic system exists in Lego, but when one takes the direct energy transfer of liquid in to account a purely mechanical representation is in some ways better than pneumatic. 

We all accept some lack of realism with Lego. I find it fun to try and make functions that have semblance to the real thing even if it is something as hard to compare as diesel/hydraulic to electric/electro-mechanical. 

Hi 

U do not use age as reference; because I've noticed that long time ago (working last 12 years in education) that you do not need to be older in order to be smarther; you learn whole life long and die as dope 

So with your attitude you are more serius and mature than most of my colleges (ok they are stucked in communism...).

For cvt idea and LEGO solution is based on parts available. It is always cool to accept the challenge, but first you're making what you are certarin and then the rest. Dont stuck like me on self propeller sprayer model on front right wheel hub for half a year, where hydrostatic drive can not be represented correctly but with gears that slide beause this machine has independent all wheel suspension, so I agree on lack of LEGO realism because of parts

7 hours ago, I_Igor said:

Hi 

U do not use age as reference; because I've noticed that long time ago (working last 12 years in education) that you do not need to be older in order to be smarther; you learn whole life long and die as dope 

So with your attitude you are more serius and mature than most of my colleges (ok they are stucked in communism...).

For cvt idea and LEGO solution is based on parts available. It is always cool to accept the challenge, but first you're making what you are certarin and then the rest. Dont stuck like me on self propeller sprayer model on front right wheel hub for half a year, where hydrostatic drive can not be represented correctly but with gears that slide beause this machine has independent all wheel suspension, so I agree on lack of LEGO realism because of parts

Fair enough, but I feel a need to try and I think I have improved on the existing cvt design a little. As for all wheel independent suspension I was thinking of 2L rubber liftarms to provide a dense and short travel for the casters,  but more on that later.

I have made nothing but failed attempts at all stages, but it all comes with learning about the challenge that I have taken on. So the more mistakes the better as long as I learn something to help me move forward. 

Off topic: my parents are from the eastern block and they got out in 81. I feel like I know what you are talking about from experience with respect to being stuck in communism. 

Don't be demoralized, it is not a failure it is development, and testing new optimized solutions is natural way of development. Without that we will be steel hanging on trees, hm or in communism or sympthize left oriented politics that call itself liberal democracy 

There is one important rule in life - only when people hit the lowest point in life they are ready to change. So when you got to dead end with development of some part for your moc, try another way, take a rest a day or two, nothing is burning and eventualy you will succeedd and that will be one great experience...everybody had a bad project - there is even topic about that here on Eurobricks. Lucky for me that I did not document my failures 

Edited July 23, 20177 yr by I_Igor

So the latest failure is that I built the cvt in shoe size and only realized after(in my overzealous attempt at ingenuity) that I used the open diffs in a way that does not work, so back to the drawing board on how to fit it all in.

Edited July 23, 20177 yr by cloud

43 minutes ago, cloud said:

so back to the drawing board

...like this

After much rework of the same idea, I've got a design that is working.

In this image one can see the sprocket solution that I am using at the moment, but it works reasonably well so unless it fails under stress conditions(which is why the sprocket is driven from both sides) it should be fine.

A couple more images on the blog including the front side view.

@cloud this solution looks good 

Over the weekend I managed to fully build one shoe and solved some wheel placement problems as well as started to add structural support for the x-brace and body.

I was able to test the shoe and the performance was mediocre. It has lots of torque and does go up and down in gear ratios as needed.  Going up an incline seems fine and it is slow as expected.

The problem seems to be that the many dive axles that twist and retain a lot of torsional power like a spring that lets loose once the friction on the drive line is reduced. The end result is a lurching of the shoe on flat ground.

This is probably exacerbated by the final output shaft having a 1:1 drive ratio with the drive sprocket.

I'm going to try a 1:2 gear ratio at the drive shaft.

If that fails I'm thinking I have to redesign the cvt to pass power more directly by gears than by axles. I can't see that being possible, but I haven't tried that yet.

Anyone have other ideas as how to lessen the impact of axle twist/spring?

I found this page on the importance of axle reinforcement and ways to do it.

I'll be trying these options first and see if it helps.

6 hours ago, cloud said:

I found this page on the importance of axle reinforcement and ways to do it.

I'll be trying these options first and see if it helps.

That is very useful