Are Transmissions necessary in Tracked Vehicles?

[Tommy Styrvoky]

I have begun working on a 1/15th TIger I Ausf E and i thought about putting a transmission in it , but after building a 3 speed sequential transmission and installed it. I am beginning to worry there won't be enough space for a compressor, turret ring traverse, battery box ,and a mechanism with adders for the engine to simulate a increase in idling speed when driving forwards. I have used a transmission in 2 other tanks ( it was a 2 speed) it seemed to cause a trivial effect in speed/torque. If I use a 12:20 ratio or 8:24 ratio for my drive sprockets from a XL and a IR speed remote. I think that would be better than a bulky 3 speed transmission.

Edited May 30, 2014 by Tommy Styrvoky

[Bzroom]

Skip the transmission!

[Nazgarot]

The IR speed remote works great as long as you use an subtractor for stearing.

It's very hard making to motors run at the same speed without linking them in some way (and linking them is not an option in a tracked setup), and it's very hard to control a tracked vehicle using the IR speed remote to control one track with each channel. The IR speed remote can be glitchy at the best of times, but using a subtractor it doesn't mater.

It all depends on how realistic you want to make the model. Using a subtractor is not very realistic as it wont be breaking a track to turn, but slow one down and speed up the other. But if you want very good control of the MOC a subtractor is far superior to any other setup. At the same time, using two XL motors you can gear it to have a decent top speed as well (I suggest a gearing of 3:1 using 36 and 12 tooth gears for setup with two XL, and subtractor with M motor for stearing. But you may be limited by available space...).

-ED-

[Tommy Styrvoky]

The IR speed remote works great as long as you use an subtractor for stearing.

It's very hard making to motors run at the same speed without linking them in some way (and linking them is not an option in a tracked setup), and it's very hard to control a tracked vehicle using the IR speed remote to control one track with each channel. The IR speed remote can be glitchy at the best of times, but using a subtractor it doesn't mater.

It all depends on how realistic you want to make the model. Using a subtractor is not very realistic as it wont be breaking a track to turn, but slow one down and speed up the other. But if you want very good control of the MOC a subtractor is far superior to any other setup. At the same time, using two XL motors you can gear it to have a decent top speed as well (I suggest a gearing of 3:1 using 36 and 12 tooth gears for setup with two XL, and subtractor with M motor for stearing. But you may be limited by available space...).

-ED-

I have tried to use a subtractor/adder in the past but when the model was just a chassis it had problems ( grinding and clicking of gears,low amount of torque) and this model will weigh roughly 7-9 Lbs. so I'm afraid that will break differentials/single bevels.

[TinkerBrick]

You could consider using the Lego RC unit and motors for propulsion. It's bulky but it offers proportionate speed output. And the aux port could turn the turret.

[Kelkschiz]

I have tried to incorporate both a transmission and a subtractor/adder in my builds, but as i build really big heavy tanks with powerful motors, i always seem to want to put too much torque on the gears. I have come to the conclusion that i must choose between either high speed and high torque or more control/realism, and that is a pretty easy choice for me, i rather have my models move at an impressive speed, more than anything else.

[Nazgarot]

I have a custom 6 bevel diff that might help you with power handling in a subtractor, but it requires some room as it's based of a turntable, and a bit tricky to put together.

For more pics have a look in my brickshelf (not very up to date as I've stared using dropbox to backup my creations, but the diff is there). Have a look at the strong diff v2 pics.

-ED-

[Tommy Styrvoky]

I have a custom 6 bevel diff that might help you with power handling in a subtractor, but it requires some room as it's based of a turntable, and a bit tricky to put together.

For more pics have a look in my brickshelf (not very up to date as I've stared using dropbox to backup my creations, but the diff is there). Have a look at the strong diff v2 pics.

-ED-

Maybe something with a small turntable instead of a large one and a subtractor might not work because I have the torsion bars below in the hull.

Edited May 30, 2014 by Tommy Styrvoky

[sonar]

The weight of a tank will not tolerate common differentials, assuming it is powered by 2 or more XL motors. I can see only reinforced custom diffs as posted above viable for such tracked vehicles.

To add to the same question: are there any options to replace usual technic axles to more reinforced variant? Because of all the torque directed to the sprocket, axles bend too easily and I found dust from grinding axles even when vehicle runs idle lifted above ground.

Edited May 31, 2014 by sonar

[andythenorth]

Try parts with the larger hubs, e.g. portal axles, or the hubs from the F1 car, or older steering hub parts. Works well.

[Tommy Styrvoky]

The weight of a tank will not tolerate common differentials, assuming it is powered by 2 or more XL motors. I can see only reinforced custom diffs as posted above viable for such tracked vehicles.

To add to the same question: are there any options to replace usual technic axles to more reinforced variant? Because of all the torque directed to the sprocket, axles bend too easily and I found dust from grinding axles even when vehicle runs idle lifted above ground.

I have found similar problems with grinding of parts and also bending of load bearing axles and idler and drive sprockets axles too.

[Kelkschiz]

I think its time for LEGO to make some steel technic parts ^^.

[Tommy Styrvoky]

I think its time for LEGO to make some steel technic parts ^^.

i thought about milling some parts but those would just grind away at the beams/holes.

[Tommy Styrvoky]

well i installed a 2 speed transmission (3 if you include neutral). The transmission has a 1:1, neutral , and 12:20. This is then connected to the final drive where the torque is increasesed by another 12:20. The transmission and selector only extend to the back to the end of the 3rd Road wheel and the 4th and 5th are where the turret traverse is located.

Lego Tiger I Ausf. E 1/15 (RC) by Tommy Styrvoky, on Flickr

Edited June 1, 2014 by Tommy Styrvoky

[sonar]

The round parts (road wheels) give a nice authentic design. I like it very much!

I would suggest avoiding red selector rings in transmission directly after XL motor. They have problems in keeping a locked position and can slip out at high torque (for example climbing an obstacle with such heavy tank).

Should we decrease torque and increase rpm when dealing with red clutch rings?

Edited June 2, 2014 by sonar

[Bzroom]

Looks pretty sweet!

If your goal is to put as much torque to the wheels, then right out of the motor should be the point of lowest torque. You could increase the speed, later to decrease it, but the efficiency lost would probably be a negative gain. You could use sliding gears to engage, rather than the red ring.

Edited June 2, 2014 by Bzroom

[Tommy Styrvoky]

I don't think I will have problems with the clutch drive rings because there is a linear actuator keeping them in place and a linear gearbox would be too long, I think what I have right now works the best.

Edited June 2, 2014 by Tommy Styrvoky