Power functions M motor for steering -will I burn it up?

[jimmythefly]

I just got a bunch of power functions stuff!

Before I go and use the M motor (with remote control) for steering my car, I want to make sure I'm not going to overly stress the motor. My concern is what happens at full steering lock.

So, if I create steering in the normal way, rack&pinion style, and hook the M motor to the pinion(through a reduction geartrain), how will that work? Should I use a clutch gear in there somewhere, or should I use a rubber band as a drive belt so it has some slippage? Or can I connect the motor directly to the pinion (through a recuction), with no clutch mechanism and just let the motor stop when it hits full lock and I release the remote lever?

Jimmy

[Zerobricks]

I suggest you to use a clucth gear, because a stalled motor can get warm quite fast.

[Darth Legolas]

I suggest you to use a clucth gear, because a stalled motor can get warm quite fast.

Oh my God! That's what they're used for? Well, that's genius.

I use an M-motor for everything. Besides NXT motors, that's all I have, and I have about 8, maybe more. I used an M-motor for steering on my most recent creation, and it does get very warm. There's almost no way around that on mine though, because the motor's connected to an axle that goes right through a spring box and into the steering. I'm on my way though.

[DLuders]

One could also use a Linear Actuator ( http://www.bricklink.com/catalogItem.asp?P=61927c01 ) , connected to the Power Functions Medium motor, to move the steering left and right. This setup results in slower steering movements (with no sudden lurching left and right). There's an internal clutch inside the Linear Actuator. I must admit, though, that the simple Clutch Gear ( http://www.bricklink.com/catalogItem.asp?P=60c01 or http://www.bricklink.com/catalogItem.asp?P=6542 ) is much simpler and less expensive.

[Ralph_S]

The only difficulty with a set-up as described here (incl a clutch gear) is that it'll lead to a vehicle that is pretty hard to control. It'll be fine in corners, but getting it to go in a straight line or any fast manoeuvres will be difficult.

I described an alternative system in another thread a while ago

http://www.eurobricks.com/forum/index.php?...c=36045&hl=

It uses a spring to self-center the steering. The mechanism that wasn't my idea, but I have applied it successfully to two models (a six-wheeled space vehicle and a model team fire engine). The motor simply stops when it can't go further, but since it is only in that condition for a very small amount of time I haven't experienced any problems so far.

Cheers,

Ralph

[backbone]

Best for steering is Worm Gear + Clutch.

[Ralph_S]

I disagree. IMO what you need for a properly controllable vehicle is a self-centring steering mechanism. When I first built my FDNY fire engine, it had a combination of a worm gear and a clutch. It worked, but it was a complete bastard to drive. I fiddled with it for quite a while, but was never happy because it is very hard to find a compromise between the vehicle being able to change direction fairly quickly and it being able to drive in a straight line properly. I have since updated it with self centring steering, as explained in my previous post, and it's made a massive difference. The thing turns left if I push the controller to one side and right if I push it to the other. If I let go of the controller, the vehicle moves in a straight line.

I realise that Darth Legolass mentions that in this sort of set-up the motor does get warm. I haven't noticed this issue myself, probably also because the motors are hidden deep inside the structure and because I don't drive the things around for very long. I suppose that in theory there's nothing stopping you from combining a clutch gear and a spring. I tried that when building the space tractor and ran into the problem that the torque exerted by the spring was enough to make the clutch gear slip.

Cheers,

Ralph

[Darth Legolas]

The only difficulty with a set-up as described here (incl a clutch gear) is that it'll lead to a vehicle that is pretty hard to control. It'll be fine in corners, but getting it to go in a straight line or any fast manoeuvres will be difficult.

I described an alternative system in another thread a while ago

http://www.eurobricks.com/forum/index.php?...c=36045&hl=

It uses a spring to self-center the steering. The mechanism that wasn't my idea, but I have applied it successfully to two models (a six-wheeled space vehicle and a model team fire engine). The motor simply stops when it can't go further, but since it is only in that condition for a very small amount of time I haven't experienced any problems so far.

Cheers,

Ralph

You know, I never got back to you on that. I have another question.

So I motorized the alternate model for the Ralley Truck, using the mechanism you showed me, but I have no room for the motor box, and the M-motor really does overheat.

It works well, but it has a few kinks here and there. I have trouble gearing it, as with the spring box, the gear attatched to the steering must be lined up with the axle, but so should the axle attatched to the motor and spring box. I don't really have enough room to go through the gears to do that. I also do note that it overheats a lot.

How can I fix that?

[jimmythefly]

Thanks for all the replies, guys (girls?).

I had seen some stuff on return-to-center steering using rubber bands, (on Technicbricks maybe). Ralph, thanks for the link to that previous thread, I'm off to bricklink for some hockey spring units.

I though about trying to achieve return-to-center through playing with caster angle and trail, but even if that worked I'd still have the question about if the motor would get hot at full steering lock.

Thanks again for the answers, at this point I just need to build and see where it takes me.

[Burf2000]

If it is a fast moving vechicle I would use self centering because your not going to be having it on full lock for long unless your doing donuts. If its a slow moving vechicle then use a actuato r/ worm gear or some other system that does not use the motor to keep it at a certain angle.

Only my view :)

[Ralph_S]

You know, I never got back to you on that. I have another question.

So I motorized the alternate model for the Ralley Truck, using the mechanism you showed me, but I have no room for the motor box, and the M-motor really does overheat.

It works well, but it has a few kinks here and there. I have trouble gearing it, as with the spring box, the gear attatched to the steering must be lined up with the axle, but so should the axle attatched to the motor and spring box. I don't really have enough room to go through the gears to do that. I also do note that it overheats a lot.

How can I fix that?

I haven't noticed any problems with the motor overheating. I remember driving the space vehicle around for about half an hour at an event about a year ago without any problems.

For the self centering steering you indeed need to line up everything nicely, otherwise the central position won't be a straight line, but if you've done it once is should stay in place. The motor and spring box is a far more compact set-up than one involving gears, but whether or not you can apply it obviously depends on the overall geometry. I've only applied power functions to fairly large vehicles and in both I had space to connect the motor and the spring box directly to the steering, without any gearing.

The gearing on the first version took up a lot of space, which meant that there was a massive box inside the truck's cab to cover it all.

One the new one, I was able to lower the steering set-up, as you can see in this picture by comparing how high the chassis is behind the wheels in comparison to the battery box (which stayed in the same place in the rebuild).

This allowed me to fit a flat floor in the aft of the cab.

Thanks for all the replies, guys (girls?).

I had seen some stuff on return-to-center steering using rubber bands, (on Technicbricks maybe). Ralph, thanks for the link to that previous thread, I'm off to bricklink for some hockey spring units.

I though about trying to achieve return-to-center through playing with caster angle and trail, but even if that worked I'd still have the question about if the motor would get hot at full steering lock.

Thanks again for the answers, at this point I just need to build and see where it takes me.

You're welcome. Ultimately you'll have to experiment yourself. What works for my vehicle may not work for yours.

If it is a fast moving vechicle I would use self centering because your not going to be having it on full lock for long unless your doing donuts. If its a slow moving vechicle then use a actuator/ worm gear or some other system that does not use the motor to keep it at a certain angle.

Only my view :)

I suppose that for something slow a worm gear works fine. I don't like slow though .

Cheers,

Ralph

[Jurgen Krooshoop]

I made a steering-system with an M-motor and a clutch gear, which works quite nice. You can download instructions in my Brickshelf-folder. You can see it drive & steer over

.