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  #1111  
Old 01-25-2019, 09:22 AM
Jon Thompson Jon Thompson is offline
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Default Light Housings

Jack love the concept of those light housings. Great job great posts.
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  #1112  
Old 01-25-2019, 09:45 AM
cliffrod cliffrod is offline
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I like what you're doing Jack but agree with the earlier comment about doing a rubber (actually silicone) mold of your casting ready wax positive. I was trained using waste molds- different than lost wax method but the same in the "only one chance to do it right" perspective- and have transitioned to producing a reusable mold nearly every time just to minimize the failure issue. I consider it a worthwhile effort and expense vs starting over from scratch after a minor failure. There's Lots of different products and options, from cheap and simple to $$.

I also wonder about compensation for shrinkage in the final medium. Do you know the shrink rate for the aluminum or alloy you will be using? I would expect it could be a concern for both fit into the fender (making it loose) and for fit of parts into the bezel where things will get even tighter, complicating any current tight squeeze.
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  #1113  
Old 01-25-2019, 10:42 AM
billfunk29 billfunk29 is offline
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Default Casting shrink

Thin sheet wax is available and easy to add a uniform thickness to compensate for shrinkage.
https://www.riogrande.com/product/Mo...E&gclsrc=aw.ds
I would be inclined to just add small patches where the fender interfaces. That would be easy to trim to perfection after casting.
Impressive project. Can't wait to see it finished.
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  #1114  
Old 01-25-2019, 01:44 PM
kcoffield kcoffield is offline
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Quote:
Originally Posted by Jack 1957 View Post
Still plugging away. I finished the right side housing without too much trouble. A lot of test fitting along the way. I have to fit these housings into the openings and still be large enough inside to stuff the guts into them. This side wasn't too bad.

Attachment 51150

Attachment 51151

Attachment 51152
Jack, those look to be fit up pretty close. Aluminum will shrink about .013"/1". So if they were 10" long about an 1/8" of shrink. Maybe the gasket thickness at the base may help compensate for that along the length.

What kind of wax is that? Have you previously used it for investment casting?

I have a home foundry. I may have chosen to do those in lost foam as I do a lot of that. Easy to work with and especially for just a couple pieces. Ever tried it?

Nice project and use of many fabrication processes. Looks like you're having a ball.....and will have something really nice to show for it when it's all said and done.

Best,
Kelly
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  #1115  
Old 01-26-2019, 12:43 AM
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Jack 1957 Jack 1957 is offline
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Almost done. There is a feature along the side of this lower portion on the OEM bezel. It's a concave area along the sides with a raised "frame" around the perimeter like the picture below. I'm not sure if I want to simulate that, or possibly two slashes inset in the sides.I'll decide tomorrow.

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I also need to add a boss to mount a fiber optic plastic strip that will run right down the center just inside the lense.

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To answer Kelly's questions, I'm using bees wax. There are a lot of variations with casting wax that I don't understand. Some of them are formable just by hand manipulation then seem to range on up to almost brittle. I've never used it so I stuck to what I am familiar with. I had a friend offer to do the design on a computer then 3D print them in PVA but there are so many test fit areas, plus the two buckets are not the same, so we would have to do two complete programs. There are also a lot of compound shapes that would have to be turned into a computer program. I could hand make all 4 of these housings in less time than it would take to program one. I'm not getting any younger,you know.

There is roughly 2% shrink in aluminum when it cools. I've tried my best to compensate for this with the wax molds. You can see in the picture below that I left the outer flanges about 1/8" larger all around to allow for shrinkage, sanding and polishing, plus a 1/16" gasket. Pictured below.

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As for using lost foam, it is quicker but seems difficult to get a smooth, detailed surface. Also, there are a couple traps in this mold that I don't think foam/green sand method would work well with. (But I could easily get wax to drain from.) You've seen how many different pieces it took to make these housings. I only had to heat the wax to join them. If I had to make these from foam I would have to use a hot glue gun to join the parts. If any of the glue doesn't burn away completely, the debris will be imbedded in the casting.
The frame around where the lense will fit is only 3/16" thick. I won't have enough material to grind away any serious surface defects. That's the area that I'm most concerned with, it's what shows. I couldn't even imagine trying to make that from foam. You can't bend it much and you can't put compound curves in it without carving them in. All I can do is try to anticipate any potential problems and do what I can to avoid them.
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Last edited by Jack 1957; 01-26-2019 at 12:53 AM.
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  #1116  
Old 01-27-2019, 03:58 PM
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I made up a test template to figure out the geometry of the hinges for the tail light housing. It's just a matter of trial and error till you get it to do what you want and not hit anything on the way. The part on the left represents the body and the part on the right is the tail light housing.

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The housing flips down and rearward and clears the lower portion of the body. I'll mount a stop pad on the rear hinge arm that will stop it from going too far.

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Full open from the back side. There will be one arm toward the rear where the body is pointed, and two forward where the housing is wider.

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I can put a light tension spring from the body out to the pivot point indicated below. This is an over center condition. One spring will hold the housing in the closed position, and while opening, the pivot point passes the center (full extension) and begins working to open the housing. That piece of tape in the picture below is where the spring will be.

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Last edited by Jack 1957; 01-27-2019 at 04:04 PM.
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  #1117  
Old 01-27-2019, 07:14 PM
kcoffield kcoffield is offline
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Quote:
Originally Posted by Jack 1957 View Post
To answer Kelly's questions, I'm using bees wax. There are a lot of variations with casting wax that I don't understand. Some of them are formable just by hand manipulation then seem to range on up to almost brittle. ........
You want a rather low expansion wax but if you are fabricating the patterns, there's a tradeoff with how workable it is. Since you are fabricating your wax patterns, there isn't much advantage over them being wax rather than foam.....each pattern needs to be built.....and successfully cast.

Quote:
Originally Posted by Jack 1957 View Post
As for using lost foam, it is quicker but seems difficult to get a smooth, detailed surface. Also, there are a couple traps in this mold that I don't think foam/green sand method would work well with. (But I could easily get wax to drain from.) You've seen how many different pieces it took to make these housings. I only had to heat the wax to join them. If I had to make these from foam I would have to use a hot glue gun to join the parts. If any of the glue doesn't burn away completely, the debris will be imbedded in the casting.
Wrong forum but you may be surprised what can be done in lost foam in regard to shape complexity and surface finish. The hot melt glue burns out very nicely so that is not a problem. Most of my foam patterns have many glue joints. Most any shape that can be investment cast can be done in lost foam. It also comes down to what materials you are most comfortable working with. I don't want to pollute your great build thread but if you have an interest let me know and I'll PM you some links. It's a great process.

Keep up the great work.

Best,
Kelly
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  #1118  
Old 01-31-2019, 03:20 PM
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Time to give these tail light housings a tune up. I made the housings a little deep to make sure I had room to get everything in there, but I have more room than I need and it is more important now to have clearance for the left housing to open, so I trimmed down the depth to a minimum so It would clear the body when it's being opened. I took roughly an inch of depth and rolled the top corner in to make it narrower.

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Next I need to install a small raised perch for an emblem. I'll set it partially into the lense area like the originals were.

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That's done. Next I need to make the swing arms and some mounting tabs. I could make the arms out of aluminum and cast them with the housings but I think I'm just going to make them from steel so I can test them now rather than after everything is cast. I'm experimenting here, I'm far outside my comfort zone. Stay tuned.

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  #1119  
Old 02-01-2019, 08:50 PM
fred26t fred26t is offline
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Default Really looking good

Thank you very much for the posts. Fred26T
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  #1120  
Old 02-08-2019, 07:37 PM
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After some discussion with Kelly (kcoffield. See post 1121 of this thread) he has convinced me that I can get good quality castings using the lost foam method with a much better chance of nailing it in one shot. Another reason is that if, for some reason, we don't get it right the first time, it would be much easier to make another set of molds in foam than in wax. The foam process is less involved than wax.
Sooooo, I have changed coarse and started to make foam molds. I have the tail lights ready, and I'm about half finished with the parking lamps.
I was really hustling so I didn't have time for pictures but I'll keep you posted.

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Last edited by Jack 1957; 02-08-2019 at 11:27 PM.
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