how the hell do I fix a bowed play field?

(Topic ID: 190809)

how the hell do I fix a bowed play field?


By cottonm4

1 year ago



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  • 37 posts
  • 22 Pinsiders participating
  • Latest reply 10 months ago by DNO
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#1 1 year ago

I stripped my Big Game play field last year and sent it out for art work repair and clear coat. The other day put my rails on and noticed a big bow in the middle of the play field. I have been using an aluminum to clamp it flat but as soon as the release the clamp the bow returns.

This is a big play field. How do I get this bow to go away?

Note: I have the rails attached to the lower side but it makes no difference with regards to the bowing issue.

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#2 1 year ago

That's a bad one. Was it that bad before you sent it out?
You will need to mount L or T channel to the bottom, as long as possible, that do not interfere. Lay pf upsidedown in the sun for a bit beforehand.

#3 1 year ago
Quoted from Jjsmooth:

That's a bad one. Was it that bad before you sent it out?
You will need to mount L or T channel to the bottom, as long as possible, that do not interfere. Lay pf upsidedown in the sun for a bit beforehand.

I don't know if it was bowed like this, or not, before I disassembled it last year. I just discovered this by accident two days ago.

The problem with mounting a straight piece of L or T angle to the bottom is every direction I look there is interference. It is almost as if I will need to hire a TIG welder to build me a rigid piece of lattice to clear everything.

Do you know if applying a heat lamp to the lower side for a few days, or a few hours, would help? Would that risk destroying the play field?

If it was a plain piece of plywood, I could work with that. But this has me scratching my head.

#4 1 year ago

Try bolting on the assemblies with solenoids ... The bowing should go away once the playfield is populated. Those drop target banks, flipper assemblies, and other heavier stuff should help it flatten out.

#5 1 year ago

Paging Vid.

#6 1 year ago
Quoted from megadeth2600:

Try bolting on the assemblies with solenoids ... The bowing should go away once the playfield is populated. Those drop target banks, flipper assemblies, and other heavier stuff should help it flatten out.

It seems to me like the heavy assemblies would make it sag even more, but then it was designed for all that weight. THanks for the suggestion. It will be a couple of days before I can get try this out.

In the meantime, I am all ears to anyone who wants to throw down ideas.

#7 1 year ago

To un-bow wood you can wet the backside then weight it down for several days with it bowed slightly in the opposite direction. I've gotten out some pretty bad bows that way.

#8 1 year ago

I've disassembled some Bally and Stern playfields that used staples to mount the rails. The playfield was still drilled for screws but none were populated. Maybe they'd staple the perfectly flat ones and screw the curvy ones ? I know I would :-p .

Sorry ... I forgot to add that you might want to see if you missed a screw or two for the rails. If it used staples, maybe switch to screws.

#9 1 year ago

When I swapped my Firepower after a lengthy time out of the cabinet, it was bowed similarly, I put weight on it trying to bow it back the right way. Didn't notice much change. In the end, I put all the mechs on and put it in the cabinet where it is supported by the sides...now I can't notice or measure any bow. If it was bowed the other way I would be much more concerned. I'm thinking after 30+ years, these games want to be in their "natural" state...

#10 1 year ago
Quoted from hailrazer:

To un-bow wood you can wet the backside then weight it down for several days with it bowed slightly in the opposite direction. I've gotten out some pretty bad bows that way.

I agree. I picked up a Global Warfare that had a very nasty bow in the playfield (to the point where the plunger was smacking into the wood). I made a frame out of 1x3 poplar standing on ita side. I then clamped the playfield upside down to it and used shims in the spots that were the worst (bending in the opposite direction of the warp ). Then used one of those handheld household steamers and went over the back of the playfield. I let it stay in the crazy contraption for about 2 weeks, and then checked how level it was. It was extremely close. I put it back on the frame without shims for another 2 weeks and it was perfect. Being a rare game it was a little nerve racking. If I find pics I will post them.

#11 1 year ago
Quoted from pinballj:

I agree. I picked up a Global Warfare that had a very nasty bow in the playfield (to the point where the plunger was smacking into the wood). I made a frame out of 1x3 poplar standing on ita side. I then clamped the playfield upside down to it and used shims in the spots that were the worst (bending in the opposite direction of the warp ). Then used one of those handheld household steamers and went over the back of the playfield. I let it stay in the crazy contraption for about 2 weeks, and then checked how level it was. It was extremely close. I put it back on the frame without shims for another 2 weeks and it was perfect. Being a rare game it was a little nerve racking. If I find pics I will post them.

I would really like to see the pics of your poplar frame. I have a steamer but I'm getting cold chills thinking about adding moisture to my newly clear-caoted play field.

#12 1 year ago
Quoted from hailrazer:

To un-bow wood you can wet the backside then weight it down for several days with it bowed slightly in the opposite direction. I've gotten out some pretty bad bows that way.

If you were nearby, I'd let you borrow my veneer press (basically, I big, extremely strong plastic bag with a vacuum pump attached to it). Maybe you know some woodworkers locally and can ask about borrowing one? It is much more effective and efficient than using weights. Rather than water, I think I would use this product http://www.veneersupplies.com/products/Super-Soft-2-Veneer-Softener-Conditioner.html (this place also sells vacuum veneer presses). I've only used it on veneer, which is a fraction of the thickness of playfields but it is a much better product for wood than water.

#13 1 year ago
Quoted from pinballj:

I agree. I picked up a Global Warfare that had a very nasty bow in the playfield (to the point where the plunger was smacking into the wood). I made a frame out of 1x3 poplar standing on ita side. I then clamped the playfield upside down to it and used shims in the spots that were the worst (bending in the opposite direction of the warp ). Then used one of those handheld household steamers and went over the back of the playfield. I let it stay in the crazy contraption for about 2 weeks, and then checked how level it was. It was extremely close. I put it back on the frame without shims for another 2 weeks and it was perfect. Being a rare game it was a little nerve racking. If I find pics I will post them.

One item I did last year when I broke my play field down was to paint the lower side with some gray lucite paint. I was not even thinking about Is there possibility the moisture in the paint and wonder if this could have been the start to the bowing issue.

Anyway, if I were to steam the underside of the play field or use that veneer softener, would I need to sand all of this paint I applied to the lower side of the play field?

#14 1 year ago
Quoted from cottonm4:

Anyway, if I were to steam the underside of the play field or use that veneer softener, would I need to sand all of this paint I applied to the lower side of the play field?

Regardless of whether you are using water or a softener, the answer depends on how permeable the paint is. It could vary quite a bit based on the type of paint and how many coats (and how thick).

#15 1 year ago
Quoted from Oldgoat:

If you were nearby, I'd let you borrow my veneer press (basically, I big, extremely strong plastic bag with a vacuum pump attached to it). Maybe you know some woodworkers locally and can ask about borrowing one? It is much more effective and efficient than using weights. Rather than water, I think I would use this product http://www.veneersupplies.com/products/Super-Soft-2-Veneer-Softener-Conditioner.html (this place also sells vacuum veneer presses). I've only used it on veneer, which is a fraction of the thickness of playfields but it is a much better product for wood than water.

A vacuum press is for applying even pressure on something you are veneering that is large or oddly shaped - it won't help with a bowed playfield.
Veneer softener is wonderful stuff for making thin material pliable, but it won't work on anything thicker than 1/8" in thickness.

A bit of moisture on the back, clamping and some heat to dry will snap the warp out of something like that - if not, then nothing will.

#16 1 year ago
Quoted from Deadpin:

A vacuum press is for applying even pressure on something you are veneering that is large or oddly shaped - it won't help with a bowed playfield.
Veneer softener is wonderful stuff for making thin material pliable, but it won't work on anything thicker than 1/8" in thickness.
A bit of moisture on the back, clamping and some heat to dry will snap the warp out of something like that - if not, then nothing will.

Thank you for this info. Summer has arrived. Looks like I will be sanding some paint from the lower side, wetting up and clamping and placing in the sun to dry. And then cross my fingers. This will be a weekend project.

#17 1 year ago

Just keep in mind that the playfield WILL bow without being populated. Not saying THAT much, but the playfield is meant to be flat with all of the assemblies attached

#18 1 year ago

I bet if you put it all together and put it in the game it would flatten out, it might take a few days of being installed. The top and bottom will come down and by that action the center will rise up to meet it flat. Or you could populate it and then hang it upside down suspended at each end of the playfield or in a rotisserie, and the weight would pull it back closer. Then installed it might flatten better.

#19 1 year ago

I know that I have read that at least one restorer will flip the playfield upside down and screw it into the machine and just let it sit like that for a good while. If you have the time- this is likely the do no harm and wait it out approach. Water and wood is a little scary to me but apparently has been done with success-

#20 1 year ago
Quoted from Deadpin:

A vacuum press is for applying even pressure on something you are veneering that is large or oddly shaped - it won't help with a bowed playfield.

While I've never flattened a playfield, I have a good bit of experience with a veneer press. One sandwiches the playfield between two cauls (in this case, pieces of flat furniture grade plywood) and places the entire sandwich in the veneer press. The issue is one of cost. The cost of the veneer press, furniture grade plywood and softener is not insignificant. Hence my suggestion if you could find someone local that already had the materials you needed. Barring that, water and weights (or clamps) is essentially the same principle.

While I would be confident this could be addressed if it were solid wood, my concern is that a playfield is plywood. Where is the source of the pressure causing the bow? If it's in the bottom layer, the liquid will penetrate it. If a middle layer, liquid won't penetrate and to your point, it will snap back quickly. Wood can be a crazy thing.

#21 1 year ago

If you google up other threads the bowing will go away after playfield has been populated and installed. Even severely bowed playfield will self correct

#22 1 year ago
Quoted from seshpilot:

Just keep in mind that the playfield WILL bow without being populated. Not saying THAT much, but the playfield is meant to be flat with all of the assemblies attached

I need some clarification: If the play field was bowed with the convex surface being the top side of the play field I can see where adding the assemblies would add weight and draw the play field down to level. However, mine is bowed with top side being concave and the bottom side being convex. With that situation, it seems to me that the added weight of the assemblies could cause the play field to sag even more.
*********************************

Here is what I have decided to do: I'm going shipping for three pieces of aluminum I-beam from our surplus store. Then I will clamp these I-beams to the lower side of the play field using 6 clamps. It is supposed to be hot this weekend so I will put it in the sun---bottom side up--- and let it bake. I'll check it every hour and hope to see improvement. And then I will install all the assemblies and see where I am at.

I'll post my results in a couple of days and let you all know how it is going.

Thanks to everybody who offered input. It really helps when thinking things through.

#23 1 year ago

I have a playfield with a serious bow (sag). It has not "self corrected". I ended up screwing angle iron to the bottom in a couple places. One piece I raised up about 2 inches with nylon spacers for clearance. So it's attached at each side with a screw in tension and one in the center in compression if that makes sense.

#24 1 year ago

My new playfield had some bow to it but after installing all the side rails it flattened out . you can try that

#25 1 year ago

I had to make a bridge to fix a dished/bowing problem. Kind of extreme but I couldn't get a clear path across the playfield to fasten a metal support.
In your case if your cabinet has full length side rail supports that the playfield rests on (cabinet support rails, not playfield rails) then you can add screws along the playfield side rails when it is installed that will attach to the cabinet support rail underneath. This may flatten it out and over time may settle in better.

Alan

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#26 1 year ago

Where's @Vid1900? He's the resident expert.

#27 1 year ago
Quoted from trimoto:

My new playfield had some bow to it but after installing all the side rails it flattened out . you can try that

I have installed all siderails. But it is such a large play field that the rails are of no help

Quoted from P2K:

I had to make a bridge to fix a dished/bowing problem. Kind of extreme but I couldn't get a clear path across the playfield to fasten a metal support.
In your case if your cabinet has full length side rail supports that the playfield rests on (cabinet support rails, not playfield rails) then you can add screws along the playfield side rails when it is installed that will attach to the cabinet support rail underneath. This may flatten it out and over time may settle in better.
Alan

THAT might be something I could use if nothing else works. The cab does not have full length cab support rails but I could add some easy enough. And then add a crosstie with an adjustment bar/block that could rest on the cab side rail redistribute the weight.

#28 1 year ago

Kruzman made a post about playfield warping yesterday in another thread:

https://pinside.com/pinball/forum/topic/nosnew-playfields-available-as-of-june-5#post-3808671

#29 1 year ago
Quoted from P2K:

I had to make a bridge to fix a dished/bowing problem. Kind of extreme but I couldn't get a clear path across the playfield to fasten a metal support.

This is pretty much exactly what I did on mine.

#30 1 year ago

My progress so far was to obtain 4 sticks of aluminum square tubing and clamp the play field down tight. I set it out in the sun for 2 hours with lower side facing the sun. It got rather hot I and decided 2 hours of sunshine was enough. I'm going to leave it clamped for a week and cross my fingers the sun bake helped some.

I'm thinking I might set it out in the garage where it will be out of the sun and at same time get some of the heat from elevated garage temps.

Y'all pray for me, now, as I hope I even have a prayer

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1 week later
#31 1 year ago

Did you get good results?

#32 1 year ago
Quoted from KornFreak28:

Did you get good results?

Thanks for asking.

The heat helped a little bit but it also caused a couple of my inserts to raise. But also I forgot that I had bought a populated Stern play field with metal supports that screw to the rails and play field. Those supports have help some. I am keeping it clamped up as in the picture and yesterday I unclamp to check progress. If is getting flatter but I'll keep it clamped for a couple of weeks longer.

I think I will be OK but it sure was scary.

#33 1 year ago

Looking good. You could place another clamp perpendicular to those to keep things straight. I believe you are trying to soften the glue between layers, and letting it cure (cool) again while in position. the layers of wood in plywood are too thin to have much bearing on your problem.
Good luck

#34 1 year ago

For added best results, use the same methods used by bowyers in reverse.

Wet the backside (non-playfield surface) with a sponge brush, let the wood absorb the water, and use a wood scrap frame to incrementally increase pressure with thumbscrews while keeping the edges braced across the playfield. You want a "frame" not single pieces of beams. With a frame you can also add small amounts of weights (equally) to speed up the process.

Do not oversaturate the wood, you do not want it wet completely soaked, as this weakens wood fibers excessively. Gradual heat is applied in drying room. You may need to repeat the wetting process several times before the playfield is properly flat. Gauge with a level via frame release once a week.

Severity of warping determines length of bracing and time in the frame.
Minor warping will correct itself in time without intervention or requiring this technique.

Putting the the playfield in the sun is not recommended for extended periods will cause cracks and wood planking.
You cannot properly control temperature changes through the day and evening, or humidity.

#35 1 year ago

almost every playfield I get for restoration starts bowing right away. Don't worry about it. once you get everything back on it, and it's laying on the wood rails, it will flatten out.

2 months later
#36 10 months ago

For anyone who is interested, have resolved my issues with my bowed play field and I thought I should post the resolution, and what I have learned.

1st, what did NOT work was just installing the rails. All installing the rails did was straighten out the sides of the play field while leaving the center area of the play field bowed. Even after I left the play field clamped flat to some support bars for a few weeks, it would still bow up as soon as I removed the clamps.

2nd, with the play field supported above my work table on some blocks, I observed that I could press on both the top and bottom of the play field and my weight would force the play field to straighten out.

3rd, part of the solution is already built into the cabinet by the manufacturers, so when the professional play field restorers say they don't worry about warped play fields, it goes to the way cab is built. As I explain what I did, I hope it also explains how the cabinet is designed to compensate for bowed play fields.

I'll try to explain..............

With these old Sterns that I have, the play field is supported inside the cab by two "Z" brackets on each side of the cab. There are also two "H" brackets that lock the play field to the lock down bar receiver. At the top end of the cab there is a strip of wood that goes all the way across and on the lower side of this wood strip are two rubber bumpers that apply force to the play field rail at the top of the play field. These two rubber bumpers, the two "H" brackets at the lockdown bar and the "Z" brackets all apply pressure to the play field and hold it in place and keep it from rattling around when you are shipping a pin all the place.

In theory, I think these two bumpers, the "H" brackets, the "Z" brackets---and the side rails are all supposed to apply pressure to keep a play field from going into a bowed position inside the cab.

****************

I installed the two "H" brackets to my naked (side rails not installed) play field then set play field in the cab on the "Z" brackets. To the naked eye, it all looked fine but when I laid my straight edge to the play field, the bow in the field stood out like a sore thumb.

My first move in correcting the bow was to screw a 15" long piece of wood to each side of the cab to add more support to the play field than what was being offered by the "Z" brackets. This is the way the old Bally's are set up for play field side support inside the cab.

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With these two new pieces of wood installed for side support, I laid the play field back into the cab. With these new supports, the play field rocked back and forth like a rocking chair. Plus, the "H" brackets were up in the air and not resting on the lock down bar receiver as they should have been.

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These "H" brackets will be forced down to the receiver when the lockdown bar is positioned, but this lets you see the bowing problem.
**********************

The second move I made was to add a length of aluminum "L" angle to the top end of the play field. This "L" angle is measured to contact that strip of wood that goes across the top of the cab and force the top of the play field into flat position all the way across. With my "L" angle installed, the two factory rubber bumpers were no longer needed and they were removed.

(NOTE: This "L" angle offers another side benefit, too: It protects the two arch plastics from dragging and possibly breaking when you move to lift your play field).

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This shows the "L" angle sort of lurking in the back behind the top rail.

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With the top of the play field being held down with the "L" angle, I can apply pressure to the bottom end and force the "H" brackets to the lock down receiver. This forces the play field flat and it loses the bow. Now, when I install the lockdown bar, the play field is forced into flat position and my bowed play field problem disappears.

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I suppose it could be argued that I was tilting at windmills and making mountains of molehills and that the problem would have corrected itself. But what I have here is a sure thing and now I can rest easy as I start putting this pin back together.

I want to thank everybody who offered ideas and thoughts on this issue.

#37 10 months ago

A good follow-up post is always appreciated.
Glad you will have a nice Big Game!

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