New Purchase: 1986 350x!

**newby200x** · 03-02-2021, 08:40 AM

The difference on the rear fender w/ that magic eraser is remarkable. It seems like it would be ready for some 2000 grit sandpaper and then some nice polishing to bring the shine out. I've been working on and off on trying to reproduce the rear mudflap. I took the original and modeled it up on my 3D CAD software. I had it quoted through a couple different polyurethane casting companies....some were way off from my budget, but one was w/in reason. His only drawback is the shrinkage/tolerance rate. He claimed that the length of the part would be subjected to a tolerance of +/- .3" which is astronomical. He claims there are ways to tighten this up, but I haven't had time to call him and discuss these alternative ways. My next step is to 3D print my model to make sure it matches up to the original and then work on casting them in polyurethane.

**Arky-X** · 03-02-2021, 09:44 AM

That cleaned up nice!
If you are looking for a cheap alternative to painting the tank, you can get a tank cover instead. Either Ceet or Hi- flite has different colors to choose.

**wonderboy** · 03-02-2021, 10:46 AM

Hey newby200x

I know that there a lot of guys here that do the resin casting. John Swineheart did a ton of it and made some really nice parts. He used the resins from Alumilite. I looked on their site and most of their resins had a shrinkage rate of just a fraction of a percent. But the length of the mudflap is 30". When you multiply that dimension by even a fraction of a percent, you get exactly what those guys told you: +/- 0.3 inches. I agree that there is no way that would work here. Maybe an 1/8" max would be acceptable.

Alumilite does make resins that offer an order of magnitude lower shrinkage (forget what line it was) but then I think the viscosity went up. When thinking about a mold design, finding a way to get good bubble free coverage of the surface of the mudflap while still filling each of the mounting tabs seemed like a pretty tough problem to tackle.

This is what got me to thinking about make a fiberglass copy.

Keep in mind I really have minimal to no experience with either resin casting of fiberglass mold making, but hey, that's what the internet is for right? LOL!

...and yes, I'm really thinking about polishing up these things. They are honestly in nicer shape than my 85 machines (which have a lot of deep scratches).

**wonderboy** · 03-02-2021, 11:23 AM

Most of the Alumilite line shows shrinkage numbers of between 0.0041"/inch to 0.01"/inch. On a 30" long part, this means shrinkage of between 0.123" and 0.3". Too much.

They do have a line of lower shrinkage resins. The "Vac Master 50" and "Replicator 532". These have shrinkage of 0.0006" per inch. Over the 30" long mudflap, this would give 0.018" shrinkage, which would be acceptable. Problem is these seem to be VERY viscous. I think (as the name implies) these would need to use pressure (vaccuum or positive pressure) to give proper results.

**wonderboy** · 03-02-2021, 11:41 AM

Originally Posted by Arky-X

That cleaned up nice!
If you are looking for a cheap alternative to painting the tank, you can get a tank cover instead. Either Ceet or Hi- flite has different colors to choose.

I'll probably just live with it as is until I've got the money to get it painted. I've actually got an 86 250SX tank that needs paint too, so I figure I'll have them both done at the same time (with the same color white).

**newby200x** · 03-02-2021, 01:06 PM

I really don't want to try to mold the part myself as I don't have the room or time at the moment to tackle a project like that. I'd like to hear some of the suggestions that the molding company has that I have been speaking to, but I just haven't got to that point yet. Once I verify my 3D model w/ a 3D printed part, then we can have that conversation. He did state that they typically just compensate the shrink rate by "oversizing" the 3D printed version. With the pricing he gave me, if he could produce the part w/ in a reasonable tolerance and consistently, I'd be ready to pull the trigger. He believes he could produce 1000+ parts of the same tool.

**wonderboy** · 03-02-2021, 01:26 PM

If you could produce that, I think you'd be printing money.

I think the target cost would be important too. Anything over 300-400 dollars probably wouldn't work (just in my opinion). If you came in under $200, I think you'd sell as many as you could make (again, just based on my opinion). At least this are my thoughts on it. Of course, the more you can make, the less the overhead costs influence the per part price. A 1000 would really make it affordable, but I don't know if the market demands 1000 parts. I've never done anything like this either, so I don't have a frame of reference for how much demand there is for replacement parts like this. Is it a 100? 10,000? I'm guessing between 100 and 1000. Probably closer to the 100 mark.

Super fun to think about. Just know this: If you make it, I will buy it!

If you don't make it... well then I'll have to think about doing it. But I really don't think I'd be able to pull it off.

**wonderboy** · 03-02-2021, 01:29 PM

So re-reading your post a bit: you'd produce molds then from a pristine 3d printed part then, rather than an original part? I see that huge advantage in that you can oversize the 3d print by exactly the expected shrinkage rate. The only downside I see if the finishing work required to get the same surface texture as the OEM part. It is a grained finish. I think you'd want to at least get rid of the lines you get from a 3D printed part, maybe make it smooth. Lots of fun to think about!

**newby200x** · 03-02-2021, 02:18 PM

The company I have been in talks w/ can create a mold of an OEM part, or a 3D printed part. I'd rather not take the chance at possibly damaging a good original, so the next best thing would be a 3D printed part. With that said, the 3D CAD model I have is made just from me using a digital caliper and angle finder. I wouldn't consider it a 100% copy to the OEM, but it should be close enough to call it a nice reproduction. And now that I have CAD data on it, I can 3D print a few, or modify any features that might need changed. As far as surface finish, they would make the mold off of a SLA 3D printed part. This is a much nicer, smoother finish than what you typically see on less expensive, home 3D printers. These less expensive 3D printers create FDM parts, which means it's just layering lines of plastic over and over to create the part. Based on my prior experience on polyurethane casting in the office furniture industry, you should be able to spray a textured paint on the 3D printed part, or at least sand/finish how you see fit. If I do pull the trigger on this, I would likely do a pre-order, or do their MOQ first. Based on the quote I have, I would ballpark that I could sell this for around $150 shipped. That price could go down depending on how many I order and amortize the tooling costs into. I have access to a FDM printer at my work, so I can fine tune the 3D CAD file until it's near perfect. What I don't have is access to a SLA printer, so that is where my costs would start incurring.

**wonderboy** · 03-02-2021, 02:28 PM

Darn, you've got this figured out! I get it, the devil is in the details, but it sounds like you're in a really good position to pull this off. This is awesome. @ $150, I don't think you'd have any trouble selling these. I know I'll buy multiple if you bring them in at that price. Post up from time to time if you want more encouragement or unsolicited advice (LOL!).

**newby200x** · 03-02-2021, 02:50 PM

Well you gave me some motivation at the least. I'm importing the model into our printer software right now and can hopefully print one off soon.

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