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I don't know if this has been shared before, but in cases where max precision is more important than min friction, it may help to route gears double (with equal ratios of course) and have the closed circuit skip one or more teeth somewhere in the circuit. That way you can have the slack in one route compensate for the slack in the other route.

When you route gears double, the gear meshes together make a closed circle. Before installing the last gear in the circle, you can sort of wind up the adjacent gears against each other to eliminate slack in the rest of the circle. Now when you install the last gear while the adjacent gears are wound up, you get a closed circle with only very little slack in it.

With the number of 'skipped' teeth I refer to the number of teeth by which the adjacent gears have been wound up, compared to their positions without wind-up.

In this simple circuit I skipped 1 tooth to obtain a transmission with practically zero slack:

Edited by Didumos69

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14 minutes ago, Technonsense said:

I use something quite similar to prevent bevel gears from slipping.

It is a good practice too and minimizes chances of slipping, but I hope it's clear that what I'm doing is different. I'm reducing rotational slack in the gear mesh, not the chances of slipping.

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Have replicated your idea and whilst it does reduced slackness, it introduces increased resistance & friction to the axle rotation by forcing the gear teeth together.
OK for slow rotation speeds but not for fast speeds.

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1 hour ago, Technonsense said:

I use something quite similar to prevent bevel gears from slipping.

 

 

It is very good idea:thumbup:

Welcome to Eurobricks

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I was originally using an extremely similar technique in my supercar chassis, but it didn't work out. Rather than steering, the u-joints leading up to the rear wheels would pop out. Maybe I used it wrong, but I don't know

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2 hours ago, Doug72 said:

Have replicated your idea and whilst it does reduced slackness, it introduces increased resistance & friction to the axle rotation by forcing the gear teeth together.
OK for slow rotation speeds but not for fast speeds.

You are right, in the example I showed, it does. This is what I tried to express by speaking of "cases where max precision is more important than min friction". However, as long as the skipped teeth don't overcompensate the slack - in the simple example I gave there is a little overcompensation - this approach will reduce slack without introducing extra friction. In the following example I have twice as many meshes and I'm also skipping a single tooth:

 

1 hour ago, I_Igor said:

Welcome to Eurobricks

Thanks :tongue:!

1 hour ago, BrickbyBrickTechnic said:

I was originally using an extremely similar technique in my supercar chassis, but it didn't work out. Rather than steering, the u-joints leading up to the rear wheels would pop out. Maybe I used it wrong, but I don't know

I have been thinking of doing something like this by duplicating the 2 u-joints in the steering setup of my rugged supercar on the right side and connecting the left and right steering wheel axles by routing a transversal axle through the dashboard. I'm not sure whether it would work out fine though.

Edited by Didumos69

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4 minutes ago, Didumos69 said:

I have been thinking of doing something like this by duplicating the 2 u-joints in the steering setup of my rugged supercar on the right side and connecting the left and right steering wheel axles by routing a transversal axle through the dashboard. I'm not sure whether it would work out fine though.

For steering wheels, I would say it could work. With the chassis, u-joints would pop out due to the resistance in the system, because all 4 wheels were steering (friction) and about 10 gears were involved.

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4 hours ago, Didumos69 said:

I'm also skipping a single tooth

I see you mention this a couple of times, but what does this actually mean? It feels like I am missing something crucial or is it exactly like @Technonsense method, but just used for a different goal? 

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45 minutes ago, Appie said:

I see you mention this a couple of times, but what does this actually mean? It feels like I am missing something crucial or is it exactly like @Technonsense method, but just used for a different goal? 

I can imagine the phrase is not completely clear. What I mean is this: When you route gears double, the gear meshes together make a closed circle. Before installing the last gear in the circle, you can sort of wind up the adjacent gears against each other to eliminate friction slack in the rest of the circle. Now when you install the last gear while the adjacent gears are wound up, you get a closed circle with only very little slack in it.

With the number of 'skipped' teeth I refer to the number of teeth by which the adjacent gears have been wound up, compared to their neutral positions. In @Technonsense's example the gears sit in their neutral positions. In my examples the gears are wound up by 1 tooth.

Edited by Didumos69

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At some point I tried to avoid “brushing teeth” by using a similar setup in a heavy duty drivetrain where 2  XL motors are powering the driveshaft from both sides. It resulted in a huge performance loss caused by the friction.

Proper bracings are important for slack reduction. The more pinholes one axle goes through, the better alignment it gets and the less slack is given at the particular gear.

To synchronize gears one should rather connect them by bypassing. In such case a better balance between slack and friction can be achieved.

640x327.jpg

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You can also do this with a single drive-train, by using two large (36- or 40-tooth gears) on a long (10+L) axle. You offset the big gears by one tooth, and the torsion in the axle keeps the tension on the drive-train.

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11 hours ago, brunojj1 said:

Proper bracings are important for slack reduction. The more pinholes one axle goes through, the better alignment it gets and the less slack is given at the particular gear.

This probably is a much more valuable best practice. In many cases it will avoid having to take odd measures as using wind-up in double routed gears. I would like to add that the farther apart the pinholes are, the better the axle is aligned.

8 hours ago, Captainowie said:

You can also do this with a single drive-train, by using two large (36- or 40-tooth gears) on a long (10+L) axle. You offset the big gears by one tooth, and the torsion in the axle keeps the tension on the drive-train.

Are you sure? What would keep the axle from loosing its torsion / wind-up?

Edited by Didumos69

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22 hours ago, Didumos69 said:

Are you sure? What would keep the axle from loosing its torsion / wind-up?

Hmm, you have me doubting myself now. Perhaps the setup I saw had some other element to it - maybe a second axle connecting both gears to the same non-torsioned shaft via two other smaller gears - I honestly can't remember.

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