I am quite new to pinball, bought my first pinball machine (TOM) for little over a year ago.
For a few months ago a member of the local pinball club asked me if i could help him with his Doctor Who MPF elevator, I am working as a mechanic and like to solve problems so of course I was interested.

Looking at the construction of the elevator and knowing they usually solve all problems by themselves made me want to do some minor changes that would make it work properly and be a reliable piece that hopefully don´t need any adjustments in the future.

An industrial piece that has to raise and lower something normally uses linear guiding and a mechanism that centers the force. But changing this elevator to something like that would take much more time and modifications than I have done on this one, and also because it is not my elevator I just tried to make it work as it is constructed to begin with.

I also got a documentation that was very helpful to have when working on the elevator, my hat´s off for that documentation made by FAZ on this forum.

The changes I did were:
• Install ball bearings instead of the non-rolling “rollers” that just slides up and down.
• Decrease friction, metal to metal that causes friction and wear is not very good.
• Align and make the bracket stiffer so it would not bend or change shape.

The work is finished and just installed in the pinball machine, I recently signed up here to present the work I have done.
I will try to show pictures and update this thread as often as I can.

At first I made a playfield and mpf dummy, I also bought a PWM controller with reverse ability. This to test and see what goes wrong when raising and lowering the elevator.

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More will be presented, it just takes some time to translate to some kind of understandable English
Unfortunately I think it will be hard to make an easy bolt on kit, some machining has to be made and the alignment is very important.
When set up with original parts and no weight it actually worked but when loading the approximately 2 kg (4.4 lb.) as the mpf weight is, the bracket started to bend when reaching the top position and finally got stuck.
With some alignment and the FAZ documentation I would probably have made it working, but there was some wear at the inside bracket and the goal was to make a better piece.
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The metal roller did not slide smooth when just moving it back and forth by hand.
The wear of the inside bracket on one side was 0.2 mm (0.007874 inch), this is probably caused by the cam shaft when rotating to the outer position of the sliding gap and then puts more pressure on one side of the bracket.

My idea of how to reduce friction was to use ball bearings and washers in another material, at first I thought of using brass as material for the washers but there was a chance that they would create filings and I was going to use ball bearings so I had to make one for each side of them to replace the rollers.
Although the bearings are sealed it might create a problem in the future.

I tried with a variant of nylon plastic which has very good resistance against wear, creates much less friction than brass and is sometimes used to replace metal. Time will tell if that was a good choice.

I have done the washer as big as possible so the abutment surface against the bracket would be as big as possible, this to help prevent the bracket from wedging.

First test in this video with only two washers on the inside worked very good, no bending and no problem with load on top.
But it didn’t felt like a long term solution, this might be the quick and easy solution for someone with elevator problem.

That is correct, just the first test with two washers and standard rollers.
The washers i might be able to provide, though i dont think it is the best solution.

I wanted more support for the plastic washers so I had to get rid of the E-clips and replace them by making M4 threads in the shafts (I know, shame on me mixing imperial and metric standard ).
The plastic washer is made in two pieces, the inner part is made of steel with a small flange for the inner part of the ball bearing to ensure that the bearing would rotate.
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Then I could fit another washer in metal above the plastic washer on each side.
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The shaft is riveted/punshed in the bracket and started to rotate while mounting a screw so I did some TIG-welding on the outside, not the job I am proudest of but the surface has some kind of treatment that made it worse.
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The toughest part was to finding out the right distance between the inner and outer bracket so that they would be parallel to each other in top and bottom position and also run smooth all the way up and down.
I made some different sizes of washers in steel and a bracket with the same distance as the mpf between the mounting hole on the inside bracket to secure that distance.
The outer bracket was also slightly bent in the bottom where the gearbox bracket is mounted so to make that straight I mounted a stiffer piece of metal in the bottom.
If it worked smooth with steel washers then it would work fine for sure with the plastic washers.
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Screws, ball bearings and some metal washers is off shelf, the rest have i done by my self.
You will at least need a lathe and a milling machine to do this for accuracy.

Centrering the force would be a big improvement, a new piece for the positions to the optosensor also has to be made

The shaft on the cam is also equiped with a ball bearing, the shaft had some minor wear from the roller.
I am not sure but i belive the shaft diameter is supposed to be 9.5mm (3/8" or 0.375"), the diameter was from 9.0mm (0.354") to 9.3mm (0.366").
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This was not a problem since it had to be machined to 9.0mm (0.354") to fit the bearing.
I made a fixture for my lathe so i could mount the cam and machine it.
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The ball bearing for the cam was made first so this video is with standard rollers and four nylon washers on the bracket.

I had to make a new bracket for the gear box so I could place the gear box a bit further away from the cam because of the washer that is behind the ball bearing.
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The new bracket is also mounted to the new brace on the bracket, this to make everything stiffer.
I made the bracket so I could fit shims between both the bracket underneath and the brace on top, the shim underneath is good to have when adjusting the height of the mpf against the playfield, I milled grooves in the three top mounting holes where the brace is mounted for the adjustment.
The shim between the gear box and the brace is for adjusting the lean angle for the cam so the distance between the cam shaft and inside bracket always stays the same in top and bottom position when the cam is rotated.
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I made a new test jig that is more accurate and easier to access when testing than the old on, the real mpf can also be tested in this jig.
The brace on top has no adjustment in sideway like the original so this jig was also needed when attaching the brace to its right position.
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Not much sideways, I'll post a video later.
It wiggled a little back and forth at top position, i made a support on each shaft for the inside bracket that slides against the inside of the outer bracket to minimize that.
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It just occured to me that the shaft diameter probably is 9.3mm (0.366") since the roller is on the other side of the E-clips and never wears out

I might be able to make some in the future, there is still some questions that needs answers from testing

How durable are the washers?
How durable are the ball bearing on the shaft of the cam?

Initially testing will be made on the one I’ve already done, I need to see for myself what to do if something goes wrong, the guys at the club are no newbies so they have full control.

It’s too much time for me at the moment in this for a beta, development time of this elevator mod with everything, fixtures etc. is somewhere near 100 hours of fun , a second piece would take about 30 hours to finish and maybe a little less after that, I have to know it’s working as I want for a beta.
And if I ever get my hands on a Doctor Who I would start developing the center force solution.

The alignment is a big issue as well when fastening the upper brace to the bracket, the washers have to slide easy and not be too loose or tight.

Not that i can think of right now, ill keep it in the back of my head

This is close, it’s really tight between the new brace and the coil. I made the brace a little thicker than the old one so I could make threads in it.
It worked fine in the test jig but could maybe cause a problem in the machine, the coil might have to be moved a bit in that case or the brace have to be made in a thinner sheet metal with a nut instead.
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Final video before installation.

That could also work, this will be a small issue to fix if there's a problem, one of those questions that needs answer from testing.

This is what I have to present at the moment of the modifications I have done, with the summer and holidays coming up it may take while until I have something more to present but I hope you enjoyed it so far. I’ll try to make a video of the elevator after installation when I get the opportunity.

Great, share your work, It would be interesting for me and others to see what solution you will come up with.

I saw that too about the same time when i signed up here
https://pinside.com/pinball/forum/topic/dr-who-mini-playfield-motor

I have been quite busy with other things and have not visited them yet so I do not know the status of the elevator, i will try to go there when i get a chance.
But i have at least been thinking of the acutator solution and im afraid it will probably not work because when the elevator is at top position it either rotates cw or ccw depending on whether it moves directly to bottom position or to the middle position.
This is just my conclusion, maybe someone who own a DW can confirm or dismiss my theory?

And im still looking to buy a DW so i might be able to come up with an bolt on solution.

Finally I went there to see how it worked, but it was broken due to opto problems and has been so for a while.
So sadly I have not much feedback to share except that the elevator worked when it was installed, they are really nice and decent guys there and i do not want to push them to fix it either.
Since im not sure about when it will be repaired it seems for the moment that i will have to wait until i get my own DW or make a second piece to someone else.