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Post by goandy on Sept 18, 2012 2:33:49 GMT -5
Job now finished. I've put a couple of photos on this first post to show what is possible- this is the ideal solution if your screen/lens is crazed or cracked. Before: New lens glued in: Finished: Back on bike: Here's how I did it. I want to replace the instrument screens in both my M models as the plastic has crazed and gone yellow. The problem is that is has a compound curve on it, which is what I want to replicate instead of just chucking a bit of flat glass or plexiglass in it. What I'm doing is taking a mold of both sides of one of my screens and then I'll heat some acrylic sheet and form it between the molds. Yes, I know acrylic will scratch but it will also polish out as well. I tried making molds out of car filler (epoxy "bog" or "bondo" to the statesiders) but the surface isn't smooth enough- the heated and pressed acrylic shows up any surface blemishes. Next up I polished the outside of the screen and used a mix of plaster of paris and cement- gives a lovely smooth, shiny surface. I've only done it today so I'll give the molds a few days to cure and then try making a screen. The inside mold was particularly difficult to extract but nothing a bit of perseverance didn't fix! **EDIT** Don't use any form of reinforcing in the mold as it will crack around them! Also, for the inside mold (male), whilst it's setting, carefully scrape the plaster away from the sides of the housing- it'll make it much easier to remove when set. Here's some photos of the progress so far:
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ap951
2nd Gear
Posts: 280
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Post by ap951 on Sept 18, 2012 21:03:15 GMT -5
I admire your attention to detail Andy, I'll be watching this to see how it turns out. I was able to polish the lens to my gauges to a fair standard however I did wonder what would I do if the lens was cracked or completely gone
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Post by goandy on Sept 18, 2012 22:40:31 GMT -5
Ha- wait till we see the finished product, then I'll see what my attention to detail is like!
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ap951
2nd Gear
Posts: 280
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Post by ap951 on Sept 18, 2012 23:13:02 GMT -5
you're way to hard on yourself Andy
I respect anyone that attempts to make a die to match the curvature of the original lens......regardless of the end result
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Post by goandy on Sept 19, 2012 5:15:58 GMT -5
Just trying to decide whether to press the hot acrylic between the two dies or use a frame and stretch it over the inside (convex) die. Anyone have any experience with this? Obviously vacuum forming it would be better but somewhat more complicated than I'd like at this stage.
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Post by goandy on Sept 25, 2012 0:26:52 GMT -5
Getting pretty close now. A few inclusions on one face for this molding but with better dust control (the acrylic is super static and attracts dust like nothing else!) it should get better. At the end of the day I can also polish any slight imperfections out. What I do is heat the acrylic sheet in the oven (DON'T TELL THE WIFE!!) for 5-10 mins at 210 celcius, but checking regularly. As soon as it's floppy, I take it out, drop it onto the female mold, line the male mold up on top and clamp them together. a few minutes later it's done. The shape is excellent so once I've got them without any surface imperfections I can start milling out the aperture in the original lens housings, cut these new screen to shape and glue them in! Exciting!
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Post by mike500 on Sept 25, 2012 7:46:18 GMT -5
looking good andy
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ap951
2nd Gear
Posts: 280
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Post by ap951 on Sept 25, 2012 19:38:08 GMT -5
I think it looks great!
I've done some vacuum forming but never with a clear acrylic, only with black ABS. Any imperfections on the mold are imprinted on the plastic so I think the way you are doing it is good. I'm just curious, what thickness of acrylic are you using?
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Post by goandy on Sept 25, 2012 23:18:26 GMT -5
I'm using 3mm acrylic sheet (that's what the local plastics business had). The factory screen is about 2.5-2.6mm. I've sanded and polished one of the molded sheets- they come up beautifully- so next step is mill the old screen out, trim new one to shape and away we go. The photos below don't really show how bad the old one is- totally crazed as well, and the other one is the same but also with a big dip in the middle (it gets quite hot down here). I used a palm sander with 400 grit to do the bulk sanding, finished off with 1200 wet and dry paper then polished with plastic compound on my polisher. I've never polished acrylic before and I'm amazed it turned out so well!
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Post by goandy on Sept 26, 2012 2:04:38 GMT -5
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Post by wayne on Sept 26, 2012 5:27:47 GMT -5
Brilliant Andy, I'll follow this with great interest. Had my instrument guy express a desire to restore RE5 gauges and nothing came of it. Even gave him old cans, lenses and an original "glass". Have a fully restored bike with crap instrument glass at the moment and am tossing around solutions.
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Post by goandy on Oct 1, 2012 6:41:16 GMT -5
Bit more progress- managed to sneak in a couple of minutes on my friend's mill and then a couple more back at home (supposed to be finishing a few jobs on the house that are 4 years old...) Milling the old screens out wasn't too bad, but hard to get a nice round corner- close enough though. I couldn't get up to the edge on either end of the screen due to the milling bit not being quite long enough so obviously this screen will lose a few points at the concours! Same for finishing the new screen to fit- all done by eye. I'll fix the screen with epoxy then after it's all set will mask it off and paint the housing in satin black to make it look pretty. Oh and before anyone asks, no, I won't be doing this for anyone else! It probably takes around 5-6 hours to do one screen spread over a few days plus all the stuffing around trying to get half decent molds made.... I'd suggest you see what Jess has in stock ;D Wayne, I'll chuck that item in the post to you in the next couple of days... Screen has a bit of a bow in it but that will be straightened when glued in place... Little bit of an improvement!
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Post by Jess on Oct 1, 2012 21:22:19 GMT -5
Andy,
Lovely work. While I appreciate the plug... That is one of the few parts I cannot supply.
Sam had a jig to replace them with Flat glass. I have not found the jig.
I appreciate clever and innovative fellows, you are apparently one.
Cheers!
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Post by wayne on Oct 2, 2012 1:12:51 GMT -5
Thanks Andy, much appreciated.
Am in the middle of a motorcycle heaven holiday, currently in Freycinet, Tasmania.
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Post by goandy on Oct 2, 2012 4:58:33 GMT -5
Thanks for the kind words Jess. When I referred people to you for a new screen (should I be asking for commission ? ), what I meant was to get a good second hand screen/instrument set..... I'm aware of the jig but seeing the amount of stuff you got from Sam I'm not surprised it's MIA. Wayne- I've heard Tassie is lovely- enjoy!
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