MOTOR AND GEARBOX SETUP.

Overview.

To get simple motion, really boils down to finding something that will move something about 9” (230mm) … this might not sound much but if its half way between the pivot point and the back of the sim, it means the back or front of the sim has 18” (450mm) of travel… That’s heaps with a sim my length.

Of course the closer to the pivot, the more force is required but the sidekick of that is you get more speed and more travel.

The options on the super cheap / junk list was boiled down to car windscreen wiper motor with a car steering box, some types of garage door openers, some types of car jacks (both mechanical and hydraulic), el cheapo car winch’s to name a few that I looked at.

I chose the car windscreen wiper motor direct coupled to a car steering box.

The motor….

The advantages of this type of 12 volt motor were… Cheap / free, most come out with dual speed, powerful for their size, have a worm drive in them, are easily reversed, will operate on a wide range of voltages (In my case 9 to 24 volt) the more volts you shove in, the higher the revs.

Its important for the electrics that the frame of the motor is not in the electrical circuit… the negative or positive are not common electrically to the body of the motor.

The motors are driven by a soft start / variable speed unit… See separate page on this.

The car steering box.

To get the right type took a bit more of an effort… it had to have about 8 to 10 inches of travel, and have a high input rev count to do it. I found the old large car ones were about right.. Holden / Ford / Falcon etc.

The turns ratio appears to be 24:1 as the arm travels about 90 degrees and it takes 6 turns of the steering wheel to do that.

I checked out “rack and pinion” type units but their travel was not enough and there was little back force resistance.

Coupling the two together….

At first I used a coupling out of the old type washing machines (basically a short bit of steam hose)… my reasoning was the hose gave flexibility on the alignment of the 2 and it would also give a crude sort of “soft start”… Well this was a total disaster… too spungy.. so I went for direct coupling the motor to the steering box.

I have used on one unit, a flexible coupling from a steering column and on the other, I welded a large nut to the Steering box input and a matching socket to the wiper motor output…. This worked great.

The motors need to be mounted with a flexible mount to allow for movement between the 2…. You WONT get them perfectly aligned.

A word on welding around these things… The Steering box has seals that you will bugger if it gets too hot, and the wiper motors generally have plastic cogs and bush’s inside so be warned.

Position sensing…

On this sort of simulator, there is no need to have exacting position sensing. All you need is feed back to the computer if its “center”, to the down from center or to the up from center. You also need a cutout if the movement is at its extreme ends…. This does not need to go to the control computer.

The basic philosophy behind ‘no real position sensing’ is really you don’t need it… after a movement and without you knowing it, the sim will return to the center position unless the control computer overrides it for some reason. This is explained on the control computer page.

I used an end cap from plastic pipes for the cam and cut out a section for the micro switch’s to determine if it was down or up from center… on center, both micro switch’s were active as the one that was normally riding the cam, fell into a groove.

There is a screw for each extreme position of the cam which activates a micro switch to stop the motor turning that way any further.

So, in short there are 4 micro switch’s… 2 to stop the motor going if the gearbox is at its extreme ends of travel and 2 to sense if its center, up from center or down from center…. Pictures tell a million words…. See the pictures.

P.S. Some pictures show the old “steam hose” couplings.

The above left picture clearly shows the groove for the centering position micro switch and the section cut out for sensing the up or down from center. There is no cutout below further to the right of the groove….

In the center position (shown) both micro switchs are not activated. (Off)

If the cam turned clockwise, only one micro switch would be activated.

If the cam moves anti-clockwise, both micro switch are activated.

The above right picture shows an experimental twin motor setup that had bike chain linking them, they were coupled to the gearbox via the “nut and socket” method.

SOME PICTURES I TOOK WHILE WRECKING IT. (June 06)

UPDATE ON THE DRIVES. (June 06)

The two motors driving a steering box worked really well and this principal is what I’m building into the new sim. Whether they actually stay there or not, time will tell.

I am allowing, during its construction, to drive the sim by “other” means if I have to … no decision as yet.

The twin drive units. (June 06)

Two wiper motors were bracketed together and joined by bike chain. (Off old bikes) and some hex tubing (machine grade) was welded to one of the sprockets.

On the steering box input shaft, I welded a suitable nut, that matched the hex tubing.

CONCLUSION.

Well it worked really well after I direct coupled the motors to the gearbox and added a soft start / variable speed unit.

The motors are on the boarder line of being too small if you want fast “fighter type” movement.

I experimented with a dual motor drive where 2 wiper motors were coupled together with bike chain…. It worked fine and I could move the drive unit up nearer the pivot and get some faster type motion.

IF I WERE TO BUILD THIS AGAIN ?

I would definitely use power assisted steering box’s as it meant I wouldn’t have to design the motion / speed around limited horse power or depending on the size /weight I would be tempted to use the existing steering boxes, each with 2 wiper motors driving them.

If I were to use power assisted steering boxes, this can easily be done by getting the whole assisted unit out of the car and running the pump with an electric motor. The oil is in a closed loop system so there is no pressure accumulator etc….. It would be very tidy.

Time will tell ????

MOTOR SPEED CORRECTIONS. (Where the motor goes one way, faster than the other way) (Added 4-02-08)

One of the things about using wiper motors, is some of them travel at a different speed going in the opposite direction. This is not a problem if you are using my FSX program as it allows for different speeds forward or backwards. There are however other software packages out there that don’t have this feature and simmers are stuck with the sim going faster on one direction than the other. This is easily fixed.

The speed DIFFERENCE is the result of the orientation of the brushes to the magnets within the outer body (stator). All you need to do is rotate slightly the outer body (that has the pole magnets glued to it on the inside) in relation to the brushes that are (normally) on the plate that stays with the gearbox.

Taking a wiper motor to bits can be a can of worms for the unprepared but if you are careful and take the motor to pieces very carefully, you should have no trouble actually doing this. The main trick is to NOT allow the rotor (the bit with all the windings on it) to actually come out of the gearbox end of the unit. If you NEED to totally remove the outer body to modify the screw holes ,,, try to make sure the rotor stays in place and it is not pulled out with the “draw” of the magnets.

Most of the common ones, you don’t have to remove the motor body. You can just turn the body further around to get a hacksaw, small grinder or file onto it.

NOTE: Make sure you don’t get iron filings etc inside the motor. Any metal “dust” or filings will be drawn into the motor by the magnets.

A normal Jap wiper motor looks like this …. The arrows indicate the locating screws holding the motor body (stator) to the gearbox, on which the brushes are located.

Some have 3 screws holding them together.

Some even have a wee dowel for locating the correct position ,,, you need to file or grind this away.

You need to undo the screws and slightly rotate the body, so you end up with this ….

NOTE …. Do NOT try to take the body off the gearbox unit unless you really have to !

I have actually moved this too far ,, although this will depend on what motor you have ,,, its just to show you what I mean.

Now holding it together by some means ,, start the motor running and have it hooked up to a switch that can easily change it from forward to backward rotation.

After a while you will find the “sweet spot” where it goes the same speed forward and backwards ,,, it maybe to the left of the hole or to the right.

Mark that position.

Generally the difference is small and just cutting a slot from the hole or filing out the hole in the cover is enough to do what you want. (Depends on the motor)

The above you can do without actually taking the cover off the motor which is a real plus.

Because you found the “sweet spot” while there is no load and you were holding it together somehow ,,, you may have to do another adjustment when it is in place and there is load, so remember this when you do the bench test. (Don’t make it too final until a “in service” test.)

Here is the mod. Done ….. (all without removing the body)

There are some wiper motors that are held together another way ,,, by a sort of hockey stick bolt arrangement ,, these also can be fixed using a different method, but you need to remove the motor to do it. ….

You cut slots in the motor body so you can move it where you want. The picture says it all.

This actual unit is the original from the FS9 unit and was modified like this prior to getting the electronic speed control.

A FINAL NOTE : THE BOLTS THAT HOLD THE BODY TO THE GEARBOX NEED TO BE TIGHT OR THE BODY WILL ROTATE WHILE IN USE.

ANOTHER NOTE: THE MEANS OF ATTATCHMENT NEED TO BE RELATELY STRONG BECAUSE IN CERTAIN SITUATIONS THE WORM GEAR CAN ACT LIKE A RACK AND PINION AND IT TRIES TO FORCE THE BODY (STATOR) AWAY FROM THE GEARBOX.

Added 13-Feb 08

I have had a couple of people having trouble with the above mod so today I went out and found 3 units in my shed that had uneven speeds ,,, 2 similar to the black one (above) and a newer type with a longer narrower body.

The 2 older ones would have been fixed very easily and just slotting the body hole would have been enough to finish the job.

The change when you twisted the motor was very marked and easy to set.

The newer one was a different beast ,,,, Not a marked difference when you turned the body and it needed a swing of well over an inch to have the motor go from faster going forward to faster going backwards. It was very “soft” in its change. Very different to the older ones.

It was tested in high speed and also the low speed ,,, both showed the same effect.

This newer one had a smaller (in diameter) motor and the gearbox wasn’t “one big worm gear” … It had a series of smaller gears in it.

It appears the smaller, narrower motors are not made electrically “square” (my term) and to get a balance speed out of them, on some, you may loose too much of the original speed.

If this speed loss (and probably, torque) is a worry, then get an older one with the fatter motor. (Bigger diameter)

If some-one wants to set a speed that is beyond just slotting the holes then something like the following should suit. Every motor will be different so you will have to use your own method to suit. (I just made this as a demo and its way too long)

The arrows indicate an edge that is formed to neatly fit around the motor body and it clamps the motor, via its wee flange, to the gearbox when the screws are done up.

An important point ,,, There are heaps of different types of wiper motors ,,, BUT one thing needs to be remembered ,,,

Most wiper motors are built to travel in one direction only.

Most haven’t got a proper thrust bearing (or pad) at one end of the motor shaft.

Plus you are now turning the mechanism backwards and working the other side of the gears ,,, so it may need time to “bed in”.

So in effect,, to start with,, there is extra friction going backwards, compared to going forward.

All this fiddling should be done with the motor hooked up to an amp meter so you can watch what is happening.

While playing around ,, I was reminded of a couple of things ,,, A lot of newer wiper motors have a “thermal overload cut-out” in them ,, so if your motor stops after some heavy use and then starts again after a while ,, you will need to bridge this out. The overload here is at the end of the red wire and the brush lead (the black thing with 2 lugs on it) ,,, just join them together or bridge them out.

Another thing ,, a lot of the newer ones have filtering systems in them (to stop radio noise etc) and it would depend on how you were driving the motor and what sort of filter is fitted, whether this should be removed or not. (In this one there are 2 electrolytic capacitors) Sometimes this filtering is from brush to brush ,, other times it is brush to earth (the case).

Of course, the wiper you have could be a different animal all together ,, but ,,, the above is basic electro-mechanical principals so it should ?? work on all of them.

If you turned the body around a complete 180 degree’s then the forward is reverse and the reverse is forward, so somewhere in there is a balanced speed.

With the different ways they configure the low speed in them ,,, there is a possibility that the “center” of the high speed is different to the “center” of the low speed ,, so do all your fiddling on the speed you want to use.

The above was the method I used to “balance” my pitch motor on the original motion platform that I built around 2001 … this method was used prior to putting in electronic speed control and it worked very well. You can still see the actual motor (the one with the slot in it) in the very first picture on this page. The motor had white tape around it to stop the dust getting in the slots. (You can just see the white tape)

Added to on 13 FEB 08