pf steering

[dingosrun]

hi can anyone help me out as im trying to build a steering function but every time i put a pf motor on it the motor or the gear pulls the model apart if anyone has a plan they can share that would be great

[Ralph_S]

hi can anyone help me out as im trying to build a steering function but every time i put a pf motor on it the motor or the gear pulls the model apart if anyone has a plan they can share that would be great

I don't have instructions for any of my PF remote controlled trucks, but there are two lines of thought on PF steering.

The part that prevents your steering system from pulling itself to bits is this one

The gear starts to slip relative to the axle if more than a particular amount of torque is generated. That means that if you incorporate it into your steering system and the steering hits its stop, the gear starts slipping. Doublebricks, a Russian LEGO users group organise a competition called the Hard Truck Contest, which involves racing PF trucks and they've got instructions for the chassis on their website.

However, I have experimented with a similar system several years ago and found it awkward. The fire engine I built was fine for driving around in circles, but was terrible at driving in a straight line. Lowering the speed at which the steering moved from full lock in one direction to the other made driving in a straight line a bit easier, but made it awkward in corners. It was just no good. A friend of mine (Mark Bellis) gave me a tip on how to build on self-centering steering mechanism. I've explained it (including a link to instructions on brickshelf that somebody else made) on EB before.

I've since built several vehicles with this mechanism and modified my fire engine with it as well. You can see the latest truck I built with it in action on flickr.

Cheers,

Ralph

[Jurgen Krooshoop]

On my website Jurgens Technic Corner there are instructions for a number remote controlled PF-vehicules.

One thing is important: allways secure all the gears and axles you use for PF-drivetrains.

Edited December 27, 2010 by Jurgen Krooshoop

[dingosrun]

The part that prevents your steering system from pulling itself to bits is this one

The gear starts to slip relative to the axle if more than a particular amount of torque is generated. That means that if you incorporate it into your steering system and the steering hits its stop, the gear starts slipping. Doublebricks, a Russian LEGO users group organise a competition called the Hard Truck Contest, which involves racing PF trucks and they've got instructions for the chassis on their website.

ralph the gear you are talking about can you tell me the name or part number to look for so i can get one cheers paul

[Ralph_S]

ralph the gear you are talking about can you tell me the name or part number to look for so i can get one cheers paul

No problem. The image in my first post is clickable and brings to you straight to the matching bricklink page.

Cheers,

Ralph

[DLuders]

Besides the 60c01 "Technic, Gear 24 Tooth Clutch" mentioned before, one could consider using one "Return-to-Center Steering" solution presented on this Eurobricks post.

[Ralph_S]

Besides the 60c01 "Technic, Gear 24 Tooth Clutch" mentioned before, one could consider using one "Return-to-Center Steering" solution presented on this Eurobricks post.

Indeed. There are more ways to make self centring steering than with the hockey spring I mentioned in the discussion I linked to as well as at the start of the discussion you linked to. The topic has come up several times more in other threads as well.

I prefer the self-centring set-up with the hockey spring. I've never tried using technic 'shock absorbers' before, but looking at it I'd say it takes up rather a lot of space -which I normally don't have on the vehicles I build. It requires a special part, obviously, but it is also very compact.

Cheers,

Ralph

[Jurgen Krooshoop]

Indeed. There are more ways to make self centring steering than with the hockey spring I mentioned in the discussion I linked to as well as at the start of the discussion you linked to. The topic has come up several times more in other threads as well.

I prefer the self-centring set-up with the hockey spring. I've never tried using technic 'shock absorbers' before, but looking at it I'd say it takes up rather a lot of space -which I normally don't have on the vehicles I build. It requires a special part, obviously, but it is also very compact.

Cheers,

Ralph

I agree with Ralph that return-to-centre-steering works very comfortably and gives good controll in combination with the joystick-remote. I did notice 2 disadvantages though: every R-T-C-system I know involves a stalled motor to keep the wheels in steered-position. This will cause the motor to overheat. And it doesn't work well with the speed-controll-remote.

The return-to-centre-steering with "shock-absorbers"doesn't nessecarily take up more space. In my

I used this system, cause I couldn't fit in the hockey-spring.

[Ralph_S]

I agree with Ralph that return-to-centre-steering works very comfortably and gives good controll in combination with the joystick-remote. I did notice 2 disadvantages though: every R-T-C-system I know involves a stalled motor to keep the wheels in steered-position. This will cause the motor to overheat. And it doesn't work well with the speed-controll-remote.

The return-to-centre-steering with "shock-absorbers"doesn't nessecarily take up more space. In my

I used this system, cause I couldn't fit in the hockey-spring.

I don't actually have the speed-control remote. On my trucks it is all or nothing!

Whether you have enough space or not obviously depends on the configuration. I tend to build model team vehicles rather than technic-style. This means I tend to hide the technical bits and I can't imagine being able to do that with 'shock absorbers'. Here's a picture of my FDNY fire truck showing how compact the steering mechanism is. It's fairly long, obviously, but it's mostly hidden inside the chassis -with the motor sitting pretty much where the gearbox would on the real truck. Since the truck has a working tilt cab, I felt this was important.

FDNY Fire engine rebuilt by Mad physicist, on Flickr

I have heard people complain of motors overheating, but haven't noticed any such problems myself, probably because I don't drive the vehicles for very long. It obviously does drain the batteries. It may be possible to prevent this by combining the hockey-spring and the white torque gear, but setting it up such that the hockey spring doesn't make the gear slip might be tricky. I had a little go at trying to get this to work when I built LURCH (a PF RC neo-classic space vehicle) almost two years ago, but I felt it caused me more trouble than it was worth.

By the way, the reason why I put parentheses around shock absorbers is because the part in question might be called a shock absorber, but actually isn't.

Cheers,

Ralph

[Jurgen Krooshoop]

And again, I agree with you, Ralph. The choice between a hockey-spring and shock-absorbers depend on the shape of the rest of the vehicule. I think the hockey-spring setup will allow a better steering-lock though. And where your building style is mainly Model-team, my style is mainly studless Technic. I don't mind if some of the technic-stuff is a bit visible.

About the overheating: I did notice that the steering motor gets quite hot, but I haven't had any problems with malfunctioning motors. I guess PF-motors can take a bit of abuse. I didn't experiment with a combination of the 24z clutch gear and R-T-C-steering yet. I'm afraid that with that combination, the centering won't work well, but I'll have to try it sometime.