(Topic ID: 146388)

Dr. Who MPF "Slop"


By wxforecaster

3 years ago



Topic Stats

  • 12 posts
  • 6 Pinsiders participating
  • Latest reply 3 years ago by dsuperbee
  • Topic is favorited by 3 Pinsiders

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#1 3 years ago

There simply isn't a lot of room (maybe 1/8" at MOST) for slop allowance for the DW mini playfield to clear the front of the playfield -- even less with Cliffy's attached.

I've attached the video above to show the amount of back-to-front, and side-to-side play that I'm seeing. Is this normal? Is there anyway to resolve it? They really should have used linear actuators rather than the bizarre way the engineers converted rotational energy into the up/down motion of the MPF. Anyways, is there a way to "fix" this so I don't do any further damage? (Cliffy set #2).

#2 3 years ago

Seems pretty normal. I slotted where mine attached to the playfield so I could move it further back as I had a CPR repro with both Cliffys.

#3 3 years ago

If it doesn't hit when it goes down you are good I think...just be thankful it works!

#4 3 years ago

The play is front to back, not so much side to side (even though you are able to move it that way with your fingers).

What about a sliver of UHMW plastic tape on the inside of the bracket. This would take up the slop and it would glide straight up and down.... maybe??

Is that a repro mini-playfield? I've seen many offset 1/8" forward. People go through all kinds of gyrations to get it to fit well.

faz

#5 3 years ago

Yeah, those CPR playfields are a PITA.

#6 3 years ago

Faz,

It's original (new motor). It's actually not the top level that's the problem, it's the bottom level with the 3 entry doors. If the MPF "slops" forward while raising, one of the three posts with the mini white rubbers sometimes hits the front lips and hangs -- I imagine this is what stripped the original motor before I acquired it.

Off all the amazing engineering feats by Bally employees, this MPF is a disaster. I would reason to believe that linear actuators would have not only been cheaper w/ optos to determine position (you wouldn't have needed the specialty cut frame and gear), but this game would not have been the routing failure it was.

It really is an amazing game.

Like I said, the top level sits well and level with the playfield, so I really don't want to fill the mounting holes and re-drill. There's got to be a way to reduce the front-to-back slop -- even a fraction of an inch would solve the problem entirely.

#7 3 years ago
Quoted from wxforecaster:

Like I said, the top level sits well and level with the playfield, so I really don't want to fill the mounting holes and re-drill. There's got to be a way to reduce the front-to-back slop -- even a fraction of an inch would solve the problem entirely.

Right... that's why I'm suggesting the UHMW Plastic Strips. There's tons of applications for it. I found this one after a quick search... I don't recommend the brand/place... just the 'product description'

http://www.findtape.com/JVCC-UHMW-PE-15-UHMW-Polyethylene-Film-Tape/p749/?vid=8227&bc=F&gclid=CIbznvDh1MkCFQ2UaQodJC0ODg

Put a strip on the inside of each outer bracket. This takes up the 'slop' and it's super slippery and tough as nails.

As for Zofia Bil's design. I'm betting it was done to make it BETTER for routes; the whole thing is a tank... solid to handle a hundred years of up/down. The only reason the design falls down is an edge condition that now seems obvious. A ball getting caught on the way down warps the frame and / or strips the gear box. The only signal to stop this high-torque tank is an opto that will never hit engage if the ball is stuck.

A slip clutch on the gear box (like on your power drill) would have saved 100's of gear box failures.

faz

#8 3 years ago

It's normal to have a little play. If the clearance is tight with the cliffy a then you are going to have to sand around the opening in the playfield to create clearance.

#9 3 years ago
Quoted from pinball_faz:

Right... that's why I'm suggesting the UHMW Plastic Strips. There's tons of applications for it. I found this one after a quick search... I don't recommend the brand/place... just the 'product description'
http://www.findtape.com/JVCC-UHMW-PE-15-UHMW-Polyethylene-Film-Tape/p749/?vid=8227&bc=F&gclid=CIbznvDh1MkCFQ2UaQodJC0ODg
Put a strip on the inside of each outer bracket. This takes up the 'slop' and it's super slippery and tough as nails.
As for Zofia Bil's design. I'm betting it was done to make it BETTER for routes; the whole thing is a tank... solid to handle a hundred years of up/down. The only reason the design falls down is an edge condition that now seems obvious. A ball getting caught on the way down warps the frame and / or strips the gear box. The only signal to stop this high-torque tank is an opto that will never hit engage if the ball is stuck.
A slip clutch on the gear box (like on your power drill) would have saved 100's of gear box failures.
faz

I'm going to try this stuff!! I think this definitely could work.

Agreed on the slip clutch idea, but hey it's a 23 year old pinball machine What's done is done. I just want to get back to playing and not destroy any more Cliffy's. The only thing that should wobble in this game is the Dalek topper!

Will let you know how this turns out when I get the tape.

1 week later
#10 3 years ago

So, I bought a roll of 1/2" slick tape (UHMW) on Ebay for $5. Totally did the trick. I applied two strips on the inside front of each bracket side, which achieved the desired thickness (three strips was too thick and didn't allow for proper glide). Taking the MPF apart allowed me to troubleshoot one of the target optos that has been acting flaky as well.

Anyways, great news. The MPF raises and lowers with no slop. I don't even have side to side slop anymore. It's really dialed in and with new Cliffy's (thanks Cliff!) it looks great.

I'm not sure it's a keeper as this game is kicking my ass repeatedly, but it's finally nice to play it working.

Evan

#11 3 years ago

Evan,

That's great! Glad it worked. I don't expect this is a uniform solution, but in your video, it seemed plausible.

DW is a deceptive game. It looks so simple, but there is SO much to do and So many ways to get your butt kicked

faz

#12 3 years ago
Quoted from wxforecaster:

So, I bought a roll of 1/2" slick tape (UHMW) on Ebay for $5. Totally did the trick. I applied two strips on the inside front of each bracket side, which achieved the desired thickness (three strips was too thick and didn't allow for proper glide). Taking the MPF apart allowed me to troubleshoot one of the target optos that has been acting flaky as well.
Anyways, great news. The MPF raises and lowers with no slop. I don't even have side to side slop anymore. It's really dialed in and with new Cliffy's (thanks Cliff!) it looks great.
I'm not sure it's a keeper as this game is kicking my ass repeatedly, but it's finally nice to play it working.
Evan

That is what makes it a keeper for me

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