Attaching a motor directly to a Linear Actuator

[Moz]

For my current project it's be handy to have a motor attached to a linear actuator but next to it rather than hanging off the end. I'm trying to get two LA's operating in close proximity with only a fairly compact and highly loaded pivot axle to work with. The LA on the moving side of the joint is not heavily loaded but it would be nice if it moved fairly slowly so gearing down a bit would be nice, but extreme strength isn't required. Making it narrow would be good - it's for the powered tailgate of a dump truck so it gets attached to the side of the dump bin.

My first attempt is 3 studs wide (same as the M motor) and same length as the LA. It looks like this:

I'd really like feedback and further suggestions. It would be ok another stud wide, but not more, and lower gearing would be nice - the 8/24 gears will work but ideally lower than that if it doesn't make the thing too large. And stronger also - currently if I let the motor run at the end of the LA travel it quickly falls apart. Adding the two extra 3 axles in the 5 long half width liftarms doesn't change that.

Thanks

moz

(more photos including parts photo)

Edited October 22, 2011 by Moz

[DLuders]

@ Moz: I like your compact design! The hyperlink above to your photos was not typed correctly (i.e., it had two http's in a row and there were colons missing). Here is the correct link.

Edited October 21, 2011 by DLuders

[doug72]

Use 8/24 as final reduction but use a 24T clutch gear (white) instead of a plain 24T gear - that way it will slip before actuatotr internal clutch kicks in.

Edited October 21, 2011 by Doug72

[Erik Leppen]

If you have the room, maybe you can replace the 8/8 and 12/20 gears by a pair of 12/36. This way you need less gears and you can also get away with the 8/8 combination. Alternatively you can use a 24/24 combination or even a 8/40 combination.

[Moz]

DLuders: thanks. Fixed.

Doug72: yes, I need to buy more clutch gears and they're expensive. But necessary, I fear. At the moment it's quite practical for me to use the speed controller I have, one channel for steering and the other for this (set of) LA's. I'm hoping for some design ideas from the forum that will shake up my current setup because I can't see a better way but I'm sure there is one :)

Erik Leppen: the 36T and 40T gears are wider than the 3 stud design can accommodate, I'd need to make it 5 studs wide and I'm very reluctant to do that.

This is one place where I think a smaller, slower motor would be ideal :) In fact, TLG might even design the motor and a new LA bracket to work together, it's something that I can imagine working with their "smaller models, fewer parts" philosophy quite well. And it wouldn't be too hard, if there was a ~2mm groove in the motor it would fit one stud closer to the LA making the whole thing much easier (ie, a 12/20 or 8/24 would bridge the gap perfectly), and the squarish LA bracket is almost the right shape to do the task already. But a bracket that

The attachment point for me is the axle hole bottom right of the top picture. Having it slightly offset doesn't affect my project. Or I could use 3/4 pins and attach to the black 3 long liftarms that have a round hole colinear with the LA.

[Alasdair Ryan]

I was bored so i made you another way of mounting a motor onto a LA,it is the same size as yours but mayby a bit stronger?

Sorry for those who are now color blind.

Edited October 25, 2011 by Alasdair Ryan

[Moz]

I was bored so i made you another way of mounting a motor onto a LA,it is the same size as yours but maybe a bit stronger?

Looks interesting. I think I need to get some of those LA mounting blocks and have a play. It looks stronger, as well as simpler, albeit it'll move a lot faster. I wonder if it might be worth using two 8T cogs instead of the 24T on the motor. I'll have a play.

thanks for the idea.

Moz

[Moz]

Looks interesting. I think I need to get some of those LA mounting blocks and have a play.

OK, just looking on BrickLink and those mounts are $8 each. And there's a total of 7 for sale. Since I need 12 or 14 of whatever I use, that's not going to work. The cost also rules it out. I'll just have to eat 8T gears instead.

[Alasdair Ryan]

I have built another idea which you can see below:

I have added a lxf file below so you can build it yourself.

compact linear actuator design 1.lxf

[timslegos]

I have built another idea which you can see below:

I have added a lxf file below so you can build it yourself.

compact linear actuator design 1.lxf

Nice Design! Very compact and sturdy.

tim

[Alasdair Ryan]

I am glad you like it.

Edited November 6, 2011 by Alasdair Ryan

[Stephen Provoost]

I have built another idea which you can see below:

I have added a lxf file below so you can build it yourself.

compact linear actuator design 1.lxf

I was also searching for this.

Thank you :)

[Alasdair Ryan]

Your welcome.

[Moz]

I have added a lxf file below so you can build it yourself.

compact linear actuator design 1.lxf

Interesting. Going with your idea of making it a stud wider I've used 5x3 L liftarms on my design above with the 3x3 half width liftarms outside them so give a stronger structure and let me use the 8:24 gears for slower movement. It uses more pieces than your design and still has the 8:8 gears in the middle, but it uses cheaper pieces and moves more slowly which is useful. Now I have to decide whether it's worth the extra width in my project. My problem is that it's hard to support the unit on both sides, and they look bulky already.

[Alasdair Ryan]

Can you post a picture.

[Moz]

I really have to get a camera with a smaller sensor, this thing where I have to use a giant tripod and 10s exposure to get more than 2-3cm DoF is starting to annoy me. A cheap second hand compact camera is overdue.

Anyway, pics:

and the older version in situ:

The narrow version seems to be strong enough. Motor power is not the limit, it's the gearing. So 8:24 rather than 12:20 does help. But you can see in that last pic that this assembly already overhangs the LA underneath and looks a bit bulky. Making it wider will only make that worse.

I'm updating my road train page now, so check here for more details.

[Sokratesz]

Edited November 11, 2011 by Sokratesz