[help] Quick help with 2 XL motor gearbox.

[Mechbuilds]

Basically i need to squeeze two XL motors inside that tiny gap. (imagine the second half of the frame attached to the gray beams end.)

The black axle on the bottom with 2 red bushings is drive for front and rear axles. 
Both XL motors need to work together to spin the black axle. If possible, the tan axle on the top would spin the fake engine. I was planning on using an M motor to spin the fake engine so i can display it with engine running without moving the moc. 



But for now, How can i drive the black axle with those 2 XL motors? 
Don't have an LDD for this yet. 

[amorti]

Loxlego has been teaming two XL motors up on one axle for a while now. Start with his models for a bit of inspiration.

Feels like you're tight for space here though, do 2 XLs actually fit?

[Mechbuilds]

EDIT:
If i use 3 of 24 tooth gears and mesh them with an 8 tooth gear, that'll make the moc very very slow and i'm not convinced one 8 tooth gear can handle all the torque alone. 

That's why i asked if anyone has a different gearing solution?

Just now, amorti said:

Loxlego has been teaming two XL motors up on one axle for a while now. Start with his models for a bit of inspiration.

Feels like you're tight for space here though, do 2 XLs actually fit?

Barely with 2 stud of room behind the motors if pushed against that grey beam. 
No room on the sides or down. 
With gears, only 1 stud of room, and if i put a beam to brace it, no room behind motors. 
Very very tight fit. 

[amorti]

Could you picture the whole lot, as it fits? I'm having a hard time picturing it.

My first thought is a 36t gear on each motor, I think they'll mesh at 1:1 (they're 5 studs across, right?), then down on to a 12t. They're much more sturdy than 8t gears, and should give that speed boost same as 24:8.

What if they were both face down towards the axle? Then some mix of bevel gears, eg 20t down on to 12t. Feels.like it'd be more compact in the space within the frame, than stacking them.

[Mechbuilds]

To make it an uneaven number, the XL motors have 1 stud gap between them. So they're 11 studs width in total. 
On the center of that 11 studs width you go 2 studs down to the axle. So that's 3 studs from center of that 11 studs width to the axle itself. 


But yeah the the XL motors can be mounted upright if i modify the chassis a little bit. (the center reinforcing beam is in the way for them to be mounted upright.) But i think i can manage to modify it without too much structural weakening.  If the XL motors are mounted upright, that'd mean that there is no room for that M motor to drive the fake engine. So i'd have to make a gearbox that spins the fake engine. Totally possible and there is room for it. 
Next issue would be:
How to attach 2 upright XL motors to an axle that's going horizontally in the middle. 

[amorti]

Just realized it's 9 studs inside the frame. You'd have to stretch it to at least 10 to face the motors downward.

Driving the axle isn't a problem, use bevel gears. Ofc that needs proper re-enforcing if you don't want teeth to skip.

The fake motor could even run on a chain.

[Mechbuilds]

Hope the bigger picture helps to visualize. (that black 12 long axle on the front is reserved for a fake engine that can be in total 10 studs long)
 

[amorti]

Looks like you would have the space to stretch the central section by 2L? Then I'd put a 36t gear on each motor, facing down, meeting a central 12t or 20t (again I can't picture the mesh) to drive the axle.

Bevel gears seem happiest driven on both sides, they don't usually skip then.

[Mechbuilds]

I don't want to stretch the frame. But i think i could modify the frame so an XL motor could be mounted sideways facing the middle.
Then i would have 3 studs of room between the XL motors. I could use 4 tooth gears to turn the drive sideways and then just add two gears to redirect it down. 
Bracing the middle would be the next problem so the 4 tooth gears don't pop off. 
If i use 5 studs of room in the middle so an 7x5 frame would fit between the XL motors, the xl motors then would pop out 1 studs from the sides out of the frame. 

Also if i use 4 tooth gears (knob wheels) would it deliver the power smoothly or jerky?

[amorti]

Don't use knob wheels, very high friction.

If the motors can face each other, put a 3L axle between them with a 36t gear in the middle. You're then basically already on top of your driven axle, just put a 12t or 20t gear on there and away you go.

Edit: ah, you can fit them sideways. Got carried away and thought they'd be front to back.

Edited November 11, 2020 by amorti

[Mechbuilds]

Just now, amorti said:

Don't use knob wheels, very high friction.

If the motors can face each other, put a 3L axle between them with a 36t gear in the middle. You're then basically already on top of your driven axle, just put a 12t or 20t gear on there and away you go.

That wouldn't work because then the motors would need to face front and back instead of left and right. 
There isn't enough room for them to be mounted in that way. 
There is barely enough room for the XL motors to face eacother in sideways position if i already modify the frame itself to make room for them. 

[amorti]

So, face them to each other, put pin/axle into top and bottom of each motor and join them with #2 connectors. Put an axle through those with a 12t black gear. Should then mesh with a bevel gear on each motor? Then same trick to turn the corner to the driven axle.

Feels like there's space for 36:12 onto that last axle to get your speed up?

[Mechbuilds]

Just now, amorti said:

So, face them to each other, put pin/axle into top and bottom of each motor and join them with #2 connectors. Put an axle through those with a 12t black gear. Should then mesh with a bevel gear on each motor? Then same trick to turn the corner to the driven axle.

I'm having a hard time trying to picture what you mean. Could you show me a picture? 

Just realized the black axle is one stud too short.. Space between front and rear unniversal joints is 13 studs. So i have to use a axle to axle connector to make the axle a little bit longer.. Oops. 

[amorti]

I don't have any XL Motors spare rn. But I'll knock something up real quick.

[Mechbuilds]

Would be very easy to build this using only one XL motor.. Not sure if it'll have enough torque though.. Final gear ratio to the wheels is: 7,001:1 
If i add a gear ratio to the XL motor, it'll further modify the final gear ratio. Already at 7:1 it's not that slow but it has okay amounts of torque with 2 XL motors. 

I think there is no way to fit 2 xl motors here.. So i give up, i hope one is enough to power this massive hulk of a moc.


Here is my gearbox how to drive the fake engine. 

[amorti]

https://bricksafe.com/files/A_morti/20201111_195003.jpg

Big image. The red beams have to be XL Motors. The gearing can be as I have it, or the other way, or only 12t thick bevel gears.

That extra axle length you need... Is there space for a central differential? That gives you the bevel gear you're after, too.

Brain fart, I've put pins in as if the red beams would attach on to motors. No, they have to be motors.

Edited November 11, 2020 by amorti

[Mechbuilds]

There would be nothing to brace the lower black bewel gear so it would click horribly when torque would be applied. 

[lmdesigner42]

Would it work to have a 36:12:20 gear mesh? Or 28:20:12? Something like the below layout. I'm not sure if the final gear ratio is what you want or not though.

36 (XL) : 12 (center) : 36(XL)

                20 (output)

The only trick is to make sure the vertical gear mesh is well braced.

[Mechbuilds]

Much easier to build and brace.. Not 100% convinced it will have enough torque. 


It's so much harder to build it with 2 XL motors in this compact setting. 

[amorti]

Face one motor direct into the back of a U joint housing (I hope you have metal U joints).

Stack the other on top facing the other way direct into the fake motor, and 16t all the way down to the other U joint as you have it.

This also solves the problem of no central diff.

Edited November 11, 2020 by amorti

[Mechbuilds]

There would be room for another XL motor on the other side and the axle could come to the fake engine straight on top of the XL motor.. But the wire is in the way. And if i mount the XL motor sideways so the wire clears, then i couldn't brace the XL motor in any way. 

6 minutes ago, amorti said:

Face one motor direct into the back of a U joint housing (I hope you have metal U joints).

Stack the other on top facing the other way direct into the fake motor, and 16t all the way down to the other U joint as you have it.

Ooh you mean both XL motors stacked on top of eachother. Bottom one driving rear axle and top one driving the fake engine and front axle? 

'

Thank you so much guys! Now i have one extra motor to use as a winch! 

[amorti]

Yep, just like that.

Easy to brace, no bevels, no 8t, perfect :)

[Mechbuilds]

Just now, amorti said:

Yep, just like that.

Easy to brace, no bevels, no 8t, perfect :)

Very solid too. Sure there is a tiny bit of slack on the front axle due to so many gears but i can live with that. 

[amorti]

Can it be done with 3* 24t gears instead? 

Edited November 11, 2020 by amorti

[Mechbuilds]

16 minutes ago, amorti said:

Can it be done with 3* 24t gears instead? 

It can but i don't have any more 24t gears. So this will do.