(Topic ID: 129917)

Modified Doctor Who mpf elevator


By darkpinball

4 years ago



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  • 53 posts
  • 10 Pinsiders participating
  • Latest reply 3 years ago by darkpinball
  • Topic is favorited by 18 Pinsiders

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There are 53 posts in this topic. You are on page 1 of 2.
11
#1 4 years ago

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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#2 4 years ago

More pictures!
More pictures!
More Pictures!
More Pictures!
More Pictures!
faz

#3 4 years ago

Yes! More pics! Very interested in the bearings concept!

#4 4 years ago

SWEET! This is so sorely needed for this title! You will sell a boatload of kits I guarantee! I will take one asap!

#5 4 years ago

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.

#6 4 years ago

Sweet! I think every DW owner would be interested in this.

#7 4 years ago

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.

#8 4 years ago

I see the washers, but not the bearings. It looks like the standard rollers. Is this something different?

Someone a few years ago made rollers out of UHMW Plastic. I tried to get a set but the guy went dark on the forum.

If you end up creating some, I'm in! I should try doing this myself. I have a lathe and plastic cutting boards that can be sacrificed. However, there's that 'skill' thing I don't have for turning small parts.

More pics and vids!

btw... that's the coolest freaking test jig!!! An over-engineered wonder (like the MPF in the first place). Zofia Bil would be proud. I LOVE IT!!
faz

#9 4 years ago

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.

#10 4 years ago

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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#11 4 years ago

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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#12 4 years ago

My Doctor Who bracket assembly is very worn and has a lot of slop. I bought a new bracket assembly and rollers and I plan on swapping everything out. But something like you've done would make things more durable than just putting back the original rollers that are known to wear.

My question is, did you use any off the shelf parts for this? I assume the bearings are a part you purchased. You mentioned making washers and the brace for the bottom so I'm guessing you have access to a machine shop. Doesn't look like this is something I'm going to be able to tackle.

#13 4 years ago

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.

#14 4 years ago

Maybe the key is to change the entire motor unit to something like a linear actuator. Eliminating the side to side force. Hmmm

#15 4 years ago
Quoted from Hawk007:

Maybe the key is to change the entire motor unit to something like a linear actuator. Eliminating the side to side force. Hmmm

I think the linear actuator idea could work great however it would have to be somewhat fast! That playfield moves a little swift and the faster the ratio the less lifting force an actuator has. I used an actuator on my earth shaker to recreate the "sinking institute" and it works well but I am going to change it out for a faster one. If someone could make a successful bolt in mod for a reasonable price it might be a decent seller

#16 4 years ago

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

#17 4 years ago
Quoted from darkpinball:

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

Yea I thought about the challenge of using the opto with an actuator...you would have to relocate it & have some type of vertical arm that could trigger it with the MPF movement.

#18 4 years ago

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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#19 4 years ago

wow!

#20 4 years ago

The ball bearing for the cam was made first so this video is with standard rollers and four nylon washers on the bracket.

#21 4 years ago

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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#22 4 years ago

That is SO sweet! Nice work.

Having tools AND skills.... what a combo! I have lots of tools....but alas, a fool with a tool is still a fool

What's the top of the MPF look like at the top of the stroke? Any wobble or did that new AWESOME bearing/washer combo fix that.

Thanks,
faz

#23 4 years ago
Quoted from pinball_faz:

What's the top of the MPF look like

WITH WEIGHT

#24 4 years ago

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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#25 4 years ago

Will you be selling these once they are perfected? I want one!

#26 4 years ago
Quoted from darkpinball:

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").

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

#27 4 years ago
Quoted from QuarterGrabber:

Will you be selling these once they are perfected?

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?

#28 4 years ago
Quoted from darkpinball:

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

Consider that mostly collectors / DW worshipers are going to be applying this fix.... it probably won't be seen on route. If it does find its way on route, the operator is a class act that want's the best for his machine. If it fails, he'll kick in a few dollars for a replacement for a great machine.

Make a call for "beta" users. We'll test it out and tell you what works / what does not work.

faz

#29 4 years ago

I will gladly test anything made. This looks to hopefully solve the only problem with this game.

#30 4 years ago
Quoted from pinball_faz:

Make a call for "beta" users. We'll test it out and tell you what works / what does not work.

faz

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.

#31 4 years ago

I think the bigger issue might be the modifications that you are making to the fasteners. I can't drill/thread the posts. This could be done as a service, but the shipping would probably make it an issue.

Is there anything you can do to make the e-clips survive? Super thin / high density washers, sheet material to coat the bracket... or a sleeve that goes over the existing posts that extends the reach.

faz

#32 4 years ago
Quoted from pinball_faz:

I think the bigger issue might be the modifications that you are making to the fasteners. I can't drill/thread the posts. This could be done as a service, but the shipping would probably make it an issue.

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.

Quoted from pinball_faz:

Is there anything you can do to make the e-clips survive? Super thin / high density washers, sheet material to coat the bracket... or a sleeve that goes over the existing posts that extends the reach.

faz

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

#33 4 years ago

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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#34 4 years ago

Final video before installation.

#35 4 years ago

Maybe use a thinner gauge metal for the brace and temper it. It is now thin and indestructible.

#36 4 years ago
Quoted from Hawk007:

Maybe use a thinner gauge metal for the brace and temper it. It is now thin and indestructible.

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.

#37 4 years ago

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.

#38 4 years ago

I am at the point I need to get creative with the one I have too. The original brackets have been reworked so many times they are soft and twist very easily. I am going to borrow some of the ideas here and see if I can come up with something that works but is not as difficult for the average person to do.

#39 4 years ago
Quoted from WonkoTSane:

I am going to borrow some of the ideas here and see if I can come up with something that works but is not as difficult for the average person to do.

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

#40 4 years ago

There was a post a few (5-6) weeks ago of a unique design. I can't find the post.

The side brackets were replaced two rods about 1/2" diameter. Pully rollers (or something like that) traveled the length of the rod.

faz

#41 4 years ago

I want to put my Doctor Who back on route but the Time Expander seems to get stuck on the front/left corner at times when raising. I am defiantly looks forward to this mod since I don't think the game would be route ready again without it.

#42 4 years ago

Loosen the screws holding the bracket on the main playfield and the MPF. Then push away from that corner; retighten. If that does not do it, the frame is bent and will need to be tweaked. A bar clamp is good for tweaking.

You can also elongate the holes. Is that an original MPF surface or the CPR repro?

faz

#43 4 years ago

Thanks for the reply! I will check it out, this is the orginal MPF.

#44 4 years ago
Quoted from pinball_faz:

There was a post a few (5-6) weeks ago of a unique design. I can't find the post.
The side brackets were replaced two rods about 1/2" diameter. Pully rollers (or something like that) traveled the length of the rod.
faz

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

#45 4 years ago
Quoted from mikedetroit:

I want to put my Doctor Who back on route but the Time Expander seems to get stuck on the front/left corner at times when raising.

That is the issue I am having. When it binds the motor will quickly bend the frame of the mechanism enough to throw the entire thing out of alignment. I think that what is happening is that the metal has become so distorted over time that it does not want to hold shape any more. It is soft and pliable. Over the course of a couple of months normal movement bends it enough to bind again. I think that the life of these machines on route my be coming to an end without a new design or a full new set of brackets from somewhere.

#46 4 years ago

Maybe the trick is having the brackets remade and then tempered. They would then be almost bullet proof!

6 months later
#47 4 years ago

I pulled my Doctor Who from route last night. It upset the location but I couldn't keep buying the motors anymore. I actually think I went through at least four of them. I tried different things, read online, but after like a month of operation, the motor gears break and I have to order a replacement. The game earned enough to pay for it, but I am going to move it to a slower location and put a more reliable game in there. There really needs to be a different solution.

#48 4 years ago

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.

#49 4 years ago
Quoted from darkpinball:

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.

You the man!

1 month later
#50 4 years ago

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.

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