Fuel Vapor Separator - Design Opinions Wanted (1 Viewer)

[procomsignathid]

for the OEM part, the top fitting has an OD of 6.3mm and the bottom three fittings have an OD of 8mm. This works out to about 1/4" and 5/16" hose ID's respectively.

Both of these sizes can be had with 1/8" NPT or 1/4" male threads in terms of adapters.

EDIT, here's a comparison of thread size:

 

[procomsignathid]

Making some progress, wanted to share as I think this is pretty sweet: You can directly import part #s from the McMaster Carr catalogue in Fusion 360

 

[ducktapeguy]

That all makes sense. I could see this as "buy your own fittings" vs "include brass or SS fittings for $X or $Y". Thoughts on 1/8" NPT vs 1/4"?

1/8"NPT would be my recommendation. The smaller diameter leaves room for more material in the plastic body which is going to be weaker than either the brass or stainless. Plus if the threads ever get stripped in the nylon they can be tapped to 1/4"NPT.

 

[zerotreedelta]

+1 to the fittings vs molded barbs - I started to model one up as well, but pivoted and basically fixed my factory one with some nylon plugs and threaded barbs instead.

 

[65swb45]

I agree with @ducttapeguy about not worrying about brass. The replacement fittings that I and several other vendors have been offering for decades for the early fuel lines are brass. No one has ever reported an issue.

And if you think about it for another second, percent of the fuel passes through a slo jet, a primary main jet, power valve and secondary main jet in the carburetor itself, ALL OF WHICH ARE MADE OF BRASS.

 

[procomsignathid]

Was taking some measurements to understand how tight clearances were between the separator and the shield and lo and behold, my epoxy repair failed (not totally surprised).

So a couple things learned: JB weld is a temporary (at best) repair to fuel-related stuff and the weak spot seems to be as reported, where the hose barbs meet the body.

Definitely going with threaded holes for fittings!

I will have to lower the height of the top port by about 4mm to ensure at least 10mm of “meat” all around a hole for a 1/8” NPT fitting. I was thinking about lowering the entire body, but there’s just not that much clearance in there without doing stuff like angling the lower inserts to reduce hose tension.

 

[charliemeyer007]

Thermo-Plastics and glue must be matched correctly. https://www.amazon.com/J-B-Weld-50139-Plastic-Adhesive/dp/B01IBOK7FE has worked the best for me on slick plastic. Hot rodding the plastic with a red hot small wire and then stitching the repair in place with glue - thread can be wire/fabric/plastic - followed by a nice thick layer of glue over top, maybe reinforced with some fabric, metal mesh.

 

[procomsignathid]

OK, after wrestling with the design a bit (mostly getting comfy using Fusion 360), I have a prototype design that uses 1/8" NPT brass fittings and brass M6 heat inserts. Ordering some parts / taps and will be printing out the first prototypes soon (will be doing PLA for the first few go-arounds until I have the slicer / supports set up properly).

All the fittings have around 10mm of meat all around, and it stays within the footprint of the original. I made sure to position the mounting points for the host adapters such that the end of the metal barbs is exactly where the end of the plastic barbs are on the OEM part, with the exception of the top barb which is 4mm lower (again to give more meat to the adapter threads).

Here's some renders for those curious:

 

[charliemeyer007]

Awesome. I just ordered a 4 pack of 304 1/4x1/4 @$8 of stainless ones from amoron.

Have you worked out the price yet?

 

[procomsignathid]

Not yet, here's all the steps I have left to do:

• Test prints (PLA) to ensure I have a good slicer setup / supports in the right spot, also to verify fitment
• Print in HDPE and/or Nylon, pressure-test before/after a week-long soak in some gas. Thoughts on target PSI?

Once I have those steps down I'll figure out price. Without the brass hardware, I want it to be well-below the going rate for an OEM replacement. It depends on how much filament these things consume really.

 

[charliemeyer007]

I don't know aren't they sort of vacuum to 1 atm systems - I know some tank/systems will burp when you open the cap indicating pos pressure build up and other will suck in air indicating a vacuum or the check engine light comes on for a vacuum leak. I would think 30 PSIG would amount to 100% safety pressure.

I'd make use test gasoline had ethanol and some (methanol gas dryer) plus some common fuel system treatment stuff in the correct dose rate. Last thing you want is to have some trace chemical dissolve/embrittle you plastic. UV and ozone are known to hard on plastic.

You should look into being a LLC - a corporate veil to hide behind could be useful in litigious times
Not sure if it could be patented or if its worth the money/effort to do but copywrite/trademark are cheap enough - or was - who know these days.

 

[procomsignathid]

I don't know aren't they sort of vacuum to 1 atm systems - I know some tank/systems will burp when you open the cap indicating pos pressure build up and other will suck in air indicating a vacuum or the check engine light comes on for a vacuum leak. I would think 30 PSIG would amount to 100% safety pressure.

I'd make use test gasoline had ethanol and some (methanol gas dryer) plus some common fuel system treatment stuff in the correct dose rate. Last thing you want is to have some trace chemical dissolve/embrittle you plastic. UV and ozone are known to hard on plastic.

You should look into being a LLC - a corporate veil to hide behind could be useful in litigious times
Not sure if it could be patented or if its worth the money/effort to do but copywrite/trademark are cheap enough - or was - who know these days.

All good suggestions, thank you! I'll definitely be setting up a few tests, and love the idea of additives / gas dryer.

 

[ducktapeguy]

There's very little pressure in these things, <1psi if the EVAP system is working. Any more than that and it'll feel like your gas tank is gonna explode.

Material cost is probably pretty minimal, print time/labor cost is what's gonna drive the price. The good thing is the size/shape/geometry for this part isn't critical, as long as there's 4 ports it'll probably work. You might be able to minimize the time by redesigning certain features. For example, the OEM part has baffles that don't connect all the way to the top. You don't have to follow that exactly, it might be better to just make the baffles full length and add in some holes between the chambers. You might even need to add in more baffles to support the hollow geometry. Even the protrusion for the top port can be eliminated, the whole thing can be a giant rectangle and just use a 90 degree fitting on top. It just depends on how original you want it to look or if you just want something functional.

 

[procomsignathid]

There's very little pressure in these things, <1psi if the EVAP system is working. Any more than that and it'll feel like your gas tank is gonna explode.

Material cost is probably pretty minimal, print time/labor cost is what's gonna drive the price. The good thing is the size/shape/geometry for this part isn't critical, as long as there's 4 ports it'll probably work. You might be able to minimize the time by redesigning certain features. For example, the OEM part has baffles that don't connect all the way to the top. You don't have to follow that exactly, it might be better to just make the baffles full length and add in some holes between the chambers. You might even need to add in more baffles to support the hollow geometry. Even the protrusion for the top port can be eliminated, the whole thing can be a giant rectangle and just use a 90 degree fitting on top. It just depends on how original you want it to look or if you just want something functional.

I followed the same basic recipe as the OEM in terms of shape, partly out of nostalgia (if Im to be honest) but also to keep the positions of the hose barbs in the same positions. My thought process is that would be more of a plug-and-play thing, especially if folks were re-using their hoses, or cutting new hoses based on the old lengths.

I do agree that a redesign would certainly work, especially at the top end of it- I think all three chambers could be extended with a connecting chamber at the top, and the top port effectively coming out the side of it. it might need to be angled slightly for hose routing to the check valve, but there's more possibilities there.

RE: Cost, I think you're right... It's going to come down time to print, assemble and ship these things. If I'm a smart man, I would add in some extra to account for the time it took me to design, prototype and test iterations, plus any tooling I purchase. It's still TBD if I'm a smart man though

 

[procomsignathid]

First PLA prototype printing as I type this!

This one will be used to check dimensions, design, etc.

 

[procomsignathid]

First print in FDM came out great, so far dimensions look good. My heat-set inserts and brass adapters are arriving over the next few days, and I will check clearances as soon as I can assemble the whole unit.

Here’s a side by side with my busted separator:

 

[Augustiron]

Cool

 

[procomsignathid]

Small update, waiting for tools... Brass heat-set inserts worked well! Drill and tap for 1/8" NPT doesn't get here till Monday, so I'll need to be patient, but I have the hose barbs.

I also found a source for bolts to include. They are JIS Class-4 M6-1.0x16 SEMS bolts with upset heads and integrated lock washer / fender washer in a trivalent chromium finish (it's a mouthful, but damn I went down a rabbithole to find those). I figure if I'm going to be selling these things I would offer up the proper hardware as it's the one part that actually shows in the truck. That, and I’ve been looking for a better source for hardware than Ace.

In other news, I have a 3d printer on its way. I was encouraged by the result of the 3d print (even though its just in FDM), but given my desire to iterate I didn't want to lean to heavy on my buddy with his printer. Also, in addition to my desire to make parts / prototypes for the truck (and potentially to sell), I also have other habits, like D&D. Kids wanted one too, so it was time. Got a nice enclosed printer with a heated bed / chamber and a hardened steel nozzle, so it will be ideal for printing engineering-grade filaments like nylon, glass-fiber-reinforced-nylon, ABS, etc. Should get setup in a few days!

 

[procomsignathid]

Drill / tap arrived, even with thin-wall PLA I was able to tighten the brass adapters without cracking the print. I’m happy with how it looks! I received all my 3d printing gear and the nylon filament as well, in the process of getting set up, so did a test-fit in the mean time.

Fit works great, and it’s apparent that I was too concerned with clearance at the top so I won’t have any issue with moving it 4mm higher to get OEM positioning. I am also going to make a few tweaks to the fins so they can be printed without supports.

Anyone have a recommended tap setup? Im doing it by hand and am not 100% pleased with consistency. Its functional, but I want ‘em all straight.

 

[charliemeyer007]

You can make a small work holding jig for a vice in a bench top drill press. Wrap in plastic film than use spray foam to make the mold. Slice carefully to make two halfs or have a 3/4 thickness mold you just hold your part in. Clay will work. I made a jig for a friend to drill out AR gas ports. Clay in a box - press in AR, fill with plaster, let dry turn over pour in molten lead. He also used it to press the pin out of the front sight.

I think it looks great. I have always just free tapped holes and never had an issue in over 50 years. I like a drill press to get straight holes when its important. Drilling and tapping guns for sights and scope mounts is wonderful training. Making and installing bushing for striped out holes in things like carbs is very handy for repair of NLA stuff.

I got the Amoron stainless steel nipples the other day - they look nice for $2/each - threw them in the fitting's box