Advice please

[Lakop]

Hi Guys,

As part of my new awakening I've been refreshing my brain with pneumatics. I did not realise I had seven pneumatic cylinders, sadly though I only had three valves. Anyway, a quick look at the new lego website and new valves, pumps and tubing had arrived. I remembered how to build the compressor (all these parts by the way are when pneumatics were fairly new) and set about building a boom arm. Brilliant! Then I added it to a turntable. Fantastic! Now wouldn't it be nice if I could use the motor that controls the compressor to turn the turntable by clever use of a lever and some gears. Wonderful! Now all I need to do is ask my fellow technic legoers if they can direct me to such a technique.

I can't seem to get my head around the new motor changeover techniques. I'm sure I will but thought you guys could help.

H

[allanp]

Take a look at this page found on Blakbirds technicopedia:

http://technicopedia.com/8880.html

About half way down you can see how the synchromesh gears work to drive two selectable functions (selected via a lever) from one axle or motor.

Hope this helps.

Edited December 18, 2012 by allanp

[Alasdair Ryan]

I have made a quick device below with what I think is what you want?

Edited December 19, 2012 by Alasdair Ryan

[dhc6twinotter]

Here is something I whipped up just before the website went down. Same idea as Alasdair Ryan's, except this design places the compressor and motor in the superstructure:

[Alasdair Ryan]

Your design is better that mine...

I was just going to upload the picture when the site went down.

[Lakop]

Hi Guys and Gals,

Thanks for the images. I'll use them as my guide.

H

[Alasdair Ryan]

I am glad that we could be of assistance .

Hi Guys and Gals,

H

Who's the girl?.......must be Daniel.

Edited December 19, 2012 by Alasdair Ryan

[Lakop]

Hi,

Now then. The only problem I have now is that the two dark grey gears, not sure of the correct name, that should engage when you move the lever spin all the time. This results in everything working at once. Which we don't want. How can I stop it? They are not supposed to engage (spin) until I switch them over.

H

[legomuppet9]

Is there a two stud gap between the dark grey gears with the red piece in between them?

[Lakop]

Is there a two stud gap between the dark grey gears with the red piece in between them?

Yep. I use a axle joiner (not sure what the correct name is), then the red switchover part sits on top. I understand that the red piece should spin and engage the dark grey gears, which are non spinning, thus resulting in movement and so on.

I've just found a element list. Axle joiner, with a transmission ring on top, two 16 tooth gears (non clutch) at either side of the ring. As i understand it, the transmission ring should spin whilst the two gears remain static and only spin once engaged by the transmission ring. Problem I have is the gears are spinning once the motor is switched on.

H

[Splat]

Now then. The only problem I have now is that the two dark grey gears, not sure of the correct name, that should engage when you move the lever spin all the time. This results in everything working at once. Which we don't want. How can I stop it? They are not supposed to engage (spin) until I switch them over.

The two dark grey gears have a round hole in the middle, so they spin freely on the axle. The red 'Technic Driving Ring' slides from side to side, and engages one (and only one) of the dark grey gears at a time.

or (there are two similar versions of this piece, and it is called a 'Technic, Gear 16 Tooth with Clutch')

So in dhc6twinotter's image above, the motor is either driving the pneumatic pump, in between the two gears (neutral), or driving the worm gear which rotates the turntable.

Is there a two stud gap between the dark grey gears with the red piece in between them?

Yes, the red 'Technic Driving Ring' is two studs wide. The two dark grey gears and the red 'Technic Driving Ring' in the middle is a total of four studs wide.

In most (all?) official Lego sets, the 'Technic Driving Ring' fits over a 'Technic, Axle Connector (Ridged with x Hole x Orientation)' which then forces the Driving Ring to spin at the same speed as the axle/s going through it. The ridges on the Axle Connector help to keep the Driving Ring in place (keep it in 'gear' as it were). Therefore, when the Driving Ring engages one of the dark grey 16 Tooth Gear with Clutch, it also spins at the same speed as the axle.

You can also see how these pieces work in this video:

I've just found a element list. Axle joiner, with a transmission ring on top, two 16 tooth gears (non clutch) at either side of the ring. As i understand it, the transmission ring should spin whilst the two gears remain static and only spin once engaged by the transmission ring. Problem I have is the gears are spinning once the motor is switched on.

To use the Driving Ring, you need to use the 'Technic, Gear 16 Tooth with Clutch'. You cannot use the non-clutch version.

Alternatively, the older Differential can also be used with the Driving Ring.

[Lakop]

Hi,

I've just watched that video myself on youtube. If you look closely at about 20sec in you'll see that the right axle gear turns when the ring is in neutral position. That's my problem but more extreme as it spins at full speed. I will try that set up tomorrow and see.

Thanks

H

[Alasdair Ryan]

That is caused by friction if you are able to gear it down a bit it should go away.

[Splat]

Also make sure that you aren't making the drive-train too tight.

[Lakop]

Hi,

I'm back. Almost there. I made the moc up in the video (above) and got a result in that one gear, the left as you look at it, remained still as required but the right hand gear rotated when not engaged. I noticed though that the drive train, once joined by axle joiners, is slightly mis aligned. The second axle turns and I can imagine that it will be hitting the gear whilst turning inside it. if that makes sense. Basically I think the problem is one of friction from the axle through the gear. There's more testing to be done I think.

H

[Lakop]

Hello again at this late hour (00.50am, UK time)

A bit of a breakthrough. I've used wedge belt wheels (LDraw no 4185) to mount my drive train for the gears and transmission drive section and it's almost perfect. Less friction between the parts. Very interesting.

H