Tommy Styrvoky

Integrated dual differential steering and 2-speed transmission

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I have always wanted a compact combined transmission + dual differential steering module for tracked vehicles. Though the biggest problem with linear setups is there is a seperate transmission and subtractor module, this is rather spacious and takes up a large space inside of a vehicle's hull. The main requisites for my current solution is that it needed to fit within a 12 stud wide space (walls included) as this is a very common width of the hull for armored vehicles. It also needed to have the option to mount several XL motors to power it.

I know a Sbrick will easily solve the solution, though a complex mechanical solution is more intersting. 

I present a WIP solution, I have tested it, and it has some issues with the worm gear for neutral steering, and needs some reinforcement to some of the connections. It features a 1:1 ratio, and 3:1 ratio for the transmission. The biggest current issue is with the steering mechanism, the test chassis I was using was rather long, so neutral steering just resulted in lots of slippage in the worm gear's mounting. Though when the vehicle was driving and steering, it seemed to function correctly with little slippage. I believe there is also some slippage between the last clutch gear and 20z gear that drives the differentials, I have attempted to reinforce the structure, and it mitigated skipping of teeth, though it still encounters the issue when the mechanism is nearly stalled.

 

Green is the drive motor input.

Orange is the steering motor input.

V1.0

29917080393_15a90e3c58_c.jpgIntegrated dual differential steering with 2-speed transmission by Tommy Styrvoky, on Flickr

30251626170_b7e39daecd_c.jpgIntegrated dual differential steering with 2-speed transmission by Tommy Styrvoky, on Flickr

29917081053_373faa6283_c.jpgIntegrated dual differential steering with 2-speed transmission by Tommy Styrvoky, on Flickr

30251627560_9d97c84049_c.jpgIntegrated dual differential steering with 2-speed transmission by Tommy Styrvoky, on Flickr

LDD file if someone wants to improve the model.

 

 

I implemented the fixes, and made it one stud shorter, I also reinforced the worm gear casing, and added supports to it.

V1.1

29931783043_a81b875d99_c.jpgV1.1 by Tommy Styrvoky, on Flickr

30477508821_fef3aa582a_c.jpgV1.1 by Tommy Styrvoky, on Flickr

 

V1.1 LDD file

Version 2.0

I completely revised the steering gear, removing the worm gear and the loosely supported steering for the differentials, and increased the gear ratio from 1:2 to 1:3. This made the base unit more compact as well as reinforcing it. As I had some major issues with the previous version in some of my larger models, it failed to function correctly, and resulted in slippage and loss of power.

40973679601_08a2e222eb_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40932335722_c8f3265f9e_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40973679731_1d5534d414_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40932335782_009db1c2cf_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

V2.0 LDD file

Edited by Tommy Styrvoky

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I'm not really into dual differential steering, but this seems like a nice compact design. Is it common to use a worm gear for the steering input? I know LEGO worm gears induce a lot of friction when used in high torque applications. They push themselves hard against the pieces holding them. Maybe that is part of the grinding problem at low speed.

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4 hours ago, Tommy Styrvoky said:

I have always wanted a compact combined transmission + dual differential steering module for tracked vehicles.

LDD file if someone wants to improve the model.

Tommy, looks to be a very interesting concept.
As you say a subtractor unit plus 2-speed transmission can take a lot of room in a model as i found for my Gyrotiller MOC.

Which motors are you using for drive input and steering input ?

Have downloaded the LDD file to study and will try and make a studless version.

Doug

 

Edited by Doug72

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Tommy, I am currently building this following the LDD build pages and have a problem.

When I reached step 27 and put the 12T black double bevel gear in place, found that as the differential casing rotates it fouls the 12T double bevel gear.
It can forces itself past the black gear in one direction but not in the other.

Maybe this is the cause of the slippage you mention.

Checked and rechecked that I have built it correctly as per LDD.

Tried a 12T single bevel gear but still the same problem.

Edited by Doug72

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2 hours ago, Doug72 said:

Tommy, I am currently building this following the LDD build pages and have a problem.

When I reached step 27 and put the 12T black double bevel gear in place, found that as the differential casing rotates it fouls the 12T double bevel gear.
It can forces itself past the black gear in one direction but not in the other.

Maybe this is the cause of the slippage you mention.

Checked and rechecked that I have built it correctly as per LDD.

Tried a 12T single bevel gear but still the same problem.

that could be an issue, I guess you could always rotate the assembly 90°, so it doesn't interfere with it, that would make a lot of sense why the steering mechanism is having issues, it could be stalling out the mechanism when the differentials rotate. 

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46 minutes ago, Tommy Styrvoky said:

that could be an issue, I guess you could always rotate the assembly 90°

Tommy, tried that and works OK - turned so now vertical and supported by the 2 x 6L thin beams to the centre support with a 2L axle/with ipin and a spacer bush.

Have an idea for strengthering the worm drive mounting which will try out tonight.

I am building it between stuudless beams so have to add 1L on one side to make frame spacing 13L.

 

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Now completed this unit and it works very smoothly - increased the bracing of the worm and there is no binding anywhere or slipping of gears in either high or low gear.

Used an L motor for drive and M motor for steering - position of motors in photo just for testing purpose.

Thanks for a great compact design - I certainly will be using it and maybe upgrade my Gyrotiller MOC.

30476754691_1a22bf2632.jpgIMG_4154 by Doug Ridgway, on Flickr

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Very smart, thanks for sharing! I love especially the use of differentials in such sophisticated mechanisms :thumbup: ! Recently I was wondering how an immitation of torque vectoring of real cars could be done and this application seems to be suitable for that, although it´s kinda useless due to the "low" possible speed. A video showing it in action would be nice, but I can rebuild it myself later of course :wink:...

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2 hours ago, brunojj1 said:

Very smart, thanks for sharing! I love especially the use of differentials in such sophisticated mechanisms :thumbup: ! Recently I was wondering how an immitation of torque vectoring of real cars could be done and this application seems to be suitable for that, although it´s kinda useless due to the "low" possible speed. A video showing it in action would be nice, but I can rebuild it myself later of course :wink:...

It could be fast enough, unfortunately I just returned to college, so I don't have the pieces on hand, though I could make an animation. Basically if the final drives were removed, the outputs would be 1:1.25, and 1:3.75 in low gear, so you could just multiply that by the rpm of the motor of choice. Though the steering motor may be sort of slow.

 

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9 hours ago, brunojj1 said:

Very smart, thanks for sharing! I love especially the use of differentials in such sophisticated mechanisms :thumbup: ! Recently I was wondering how an immitation of torque vectoring of real cars could be done and this application seems to be suitable for that, although it´s kinda useless due to the "low" possible speed. A video showing it in action would be nice, but I can rebuild it myself later of course :wink:...

I guess to put it into context, the if both the drive motors are L motors. Here's a chart of the outputs at different speeds, this may help to put it into perspective, as a L motor has an output of 272 rpm at 9V

according to Sariel's site. 

https://docs.google.com/spreadsheets/d/1tia58woCgtb_IcP23C_HnrMuya34GbS6_L_fACKX1rI/edit?usp=sharing

I think I did the math correctly for this, as the values seem reasonable.

Edited by Tommy Styrvoky

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7 hours ago, Tommy Styrvoky said:

It could be fast enough, unfortunately I just returned to college, so I don't have the pieces on hand, though I could make an animation. Basically if the final drives were removed, the outputs would be 1:1.25, and 1:3.75 in low gear, so you could just multiply that by the rpm of the motor of choice. Though the steering motor may be sort of slow.

 

 

1 hour ago, Tommy Styrvoky said:

I guess to put it into context, the if both the drive motors are L motors. Here's a chart of the outputs at different speeds, this may help to put it into perspective, as a L motor has an output of 272 rpm at 9V

according to Sariel's site. 

https://docs.google.com/spreadsheets/d/1tia58woCgtb_IcP23C_HnrMuya34GbS6_L_fACKX1rI/edit?usp=sharing

I think I did the math correctly for this, as the values seem reasonable.

 

First of all – hats off that you could build this only from imagination without physical parts at hand :thumbup:!

I apologize for having made the misleading statement about too slow speed! It was meant rather regarding the relatively slow speed of any Lego application, no matter what gear reduction, even with 2 x RC motors, to implement a kind of useful and vivid torque vectoring of a car / supercar. By the way, I find Philo´s homepage very useful when it comes to motors comparison, e.g. speed/current vs. torque diagrams: http://www.philohome.com/motors/motorcomp.htm 

I have rebuilt your genius mechanism just to understand the principle and yes - this is exactly what I was looking for when I thought about torque vectoring – means that the inner wheels are spinning at lower speed than on the outside while being steered. Thanks again for sharing!

Edited by brunojj1

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2 hours ago, brunojj1 said:

 

 

First of all – hats off that you could build this only from imagination without physical parts at hand :thumbup:!

I built it in physical parts, but then I fixed the issues with it digitally. 

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Tommy, I have adapted your design to suit stud-less construction with side beams 13L apart.
The unit incorporates an Efferman worm drive housing for the steering input - it gives 8:1 and uses and two 8T gears to get correct centres.
Biggest challange was to support the two 16/24T diffs in the centre - hence the two 5 x 7 frames in the middle.
My two axle 2 speed unit is used - at present with hand change over - have to find a way to operate from outside the unit.
Fast speed 5:1 reduction
Slow speed 15:1 reduction.
L motor for propulsion and M motor for steering. Motor mountings to improve later when installed.
Final drive to tracks is 3:1 and both speeds give desired track speed and steering.
Next step build into my Gyrotiller MOC.

Underside view:
30526343341_c880879405.jpgIMG_4162 by Doug Ridgway, on Flickr

Top view:
29982852364_4b880b5853.jpgIMG_4161 by Doug Ridgway, on Flickr

Edited by Doug72

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Here's a test of a slightly updated design, it functions perfectly with little slippage, and resistance. 

I'm testing it in the chassis of my next MOC, the IS-7 Tank

30213160754_8a0c5822d5_c.jpgIS-7 chassis WIP by Tommy Styrvoky, on Flickr

30213162254_d3cdb86b6f_c.jpgIS-7 chassis WIP by Tommy Styrvoky, on Flickr

30757329521_6686f63b9f_c.jpgIS-7 chassis WIP by Tommy Styrvoky, on Flickr

And a short video of it's basic operation here

30845046575_5f972b1e0c_c.jpgdual differential steering mechanism by Tommy Styrvoky, on Flickr

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14 hours ago, Tommy Styrvoky said:

Here's a test of a slightly updated design, it functions perfectly with little slippage, and resistance. 

 

Now built this into my Gyrotiller MOC and works very smoothly with wide radius turns and turning on the spot working perfectly.
2 speed change over accessible from outside.

 

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Version 2.0

I completely revised the steering gear, removing the worm gear and the loosely supported steering for the differentials, and increased the gear ratio from 1:2 to 1:3. This made the base unit more compact as well as reinforcing it. As I had some major issues with the previous version in some of my larger models, it failed to function correctly, and resulted in slippage and loss of power.

40973679601_08a2e222eb_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40932335722_c8f3265f9e_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40973679731_1d5534d414_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

40932335782_009db1c2cf_c.jpgLego Integrated Dual differential steering and two speed transmission V2 by Tommy Styrvoky, on Flickr

V2.0 LDD file

I still need to sort out if the current option that I have for the gear selector will function correctly.

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Great mechanism, I plan on using it on my MOC but it's a little too big for my taste, so I revised it to make it smaller and made it longitudinal, and I ditched a gearbox because I don't need it. NOW, here is my question, will my concept work? Same principal as yours Tommy.

Yellow is drive input

Green is drive output

Blue is steering input

800x566.jpg

I need some feedback, pretty please. @Tommy Styrvoky, @Doug72?

Edited by pagicence
picture correction

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8 minutes ago, pagicence said:

Great mechanism, I plan on using it on my MOC but it's a little too big for my taste, so I revised it to make it smaller and made it longitudinal, and I ditched a gearbox because I don't need it. NOW, here is my question, will my concept work? Same principal as yours Tommy.

I need some feedback, pretty please. @Tommy Styrvoky, @Doug72?

Yeah your version it should work, I have a smaller design if you just want the steering portion of the mechanism. The design is system based, though it would be easy to convert to studless.

15787332573_854158aaed_c.jpgLego Adder/ Subtractor by Tommy Styrvoky, on Flickr

16405610751_2acf7d5672_c.jpgLego Adder/ Subtractor by Tommy Styrvoky, on Flickr

16221150259_91f430051e_c.jpgLego Adder/ Subtractor by Tommy Styrvoky, on Flickr

 

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This is the subtractor unit I am using for my latest MOC.
XL motor for drive and M motor with 2 stage reduction for steering.

41206082861_17cc88fae6_z.jpg

Edited by Doug72

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On 03/04/2018 at 12:27 AM, Tommy Styrvoky said:

I have a smaller design if you just want the steering portion of the mechanism. The design is system based, though it would be easy to convert to studless.

15787332573_854158aaed_c.jpg

 

Thanks for your design, your compact version is just what I am looking for to reduce overall length of the subtractor unit to fit into my Crawler Under Carriage MOC giving more room to fit a large battery box out of view.



I have made a stud-less version and eliminated the chain by using an offset 12T double bevel gear meshing with the two 16T gears.
Tested using two M motors and performs OK.
Should be able to use XL/L motor combination OK as well.


40514648394_57b0eeb5cf_z.jpg


39418918480_d4fe825d20_z.jpg

Edited by Doug72

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Thanks guys for the help, I figured it out and this is what I'll be using. With XL for drive and M for steering which can fit perfectly on top of the differentials. I really needed to be compact, symmetrical and with odd number in width, with the possibility to connect almost everywhere.

 

800x433.jpg

Edited by pagicence

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