Fuel Vapor Separator - Design Opinions Wanted (1 Viewer)

[Andrew S]

Very cool, I should buy one for the inevitable failure of my own vapor separator.

Easy option for tapping straight is to print a quick guide block with a clearance hole for the tap. Since you've already modeled your part-to-be-tapped, you can make the guide block fit snugly to the part body wherever you need it to be.

Another option is to model the threads and let them be printed. Then just run the tap through to clear out any flashing.

 

[procomsignathid]

Update:

3D printer is set up. Have a dedicated space now, plus a filament drier (the large dehydrator), a dry box for a 5KG roll of Nylon, and we're off to the races. Kids are enthralled:

Working on dialing in print settings for nylon... Aborted the first print after 15 or so layers as the edges were curling. Here's what that was looking like:

Knocked down the fan speed to keep temps up and the current print is looking much better thus far, but I can tell I'll need to be dialing in surface finish. Here's the current prototype:

They said Nylon is a PITA, and it seems to be living up to the reputation, but I think it will be manageable.

 

[charliemeyer007]

I have read that you need to dry the nylon filament to get better results.

 

[procomsignathid]

That's right, I dried it for around 6 hours at 70C / 160F, but after this print I may do a full 24h and see how that goes.

 

[procomsignathid]

The 3D-printing saga continues, but is starting to bear fruit:

In short, nylon is annoying to print, but I'm figuring it out. It wants to print super hot, and super slow compared to PLA, but I'm now starting to get surface quality I'm happy with. That said, the prints are taking awhile, the current one is about 4 hours into a 16 hour print. The wall thickness of the chamber is way too much material, so I'm going to thin it down from about 5mm to 2.5-3mm. That should hopefully speed up print time and use less material.

For those who want to delve into the madness of 3D printing, here are my attempts up to now:

1. Stopped this print after seeing poor surface quality and lots of curling. This was due to poor bed adhesion (didn't properly clean the bed first) and too much cooling in the print chamber.
2. This print failed around 90% through, likely also due to poor bed adhesion (still hadn't properly cleaned the print bed). Quality is pretty rough on the sides, only recently learned this was mostly due to under-extrusion (print speed too fast)
3. This print completed successfully, but still terrible surface quality, and some pitting/holes due to under-extrusion. I hadn't started slowing things down yet. There also may have been too much moisture in the nylon. I did use supports for this print, although they did not break away cleanly and left a terrible surface finish on the bottom. Thanks to a properly-cleaned print bed, it took real effort to remove it.
4. Turned off all cooling for this print, played around with support settings. Surface quality was not looking great still, and I noticed on the infill sections it was god-awful. This was the ah-ha moment, as the infill sections print much faster than the walls. Still can not remove the damn supports, leaves a lot of artifacts.
5. Slowed things down from ~200mm/s print speed to ~100mm/s. Quality notably improved, but not there yet. Played with support settings again, but still too much adhesion.
6. Slowed down to ~60mm/s, and now seeing much better quality. I had resolved to let this print continue, but there was a filament tangle in the dry box and it failed. I am still seeing minor curling on the overhangs, so I will play with even slower speeds or perhaps some cooling for those parts. Ditched the supports, but added a brim (much easier to remove)
7. In progres... Added some cooling to the overhangs, looks good so far. Wall quality is great. We'll see tomorrow how it looks, hoping to have the first nylon print I can pressure-test.

Circles in red: curling on 1, stuck supports on 4 and 5. Also note how thick the walls are on print 6. Aside from meat where brass threads are going, I think the walls can be half that thickness and still be plenty strong. The next photo shows more detail on the surface quality for overhangs. Left to right: first print, curling. 4th and 5th prints, stuck supports. 6th print, getting there but not there yet (no supports).

Under-extrusion (looks like scratches) due to print speed too fast:

Here's print #7 in-progress, so far so good. We're in "functional but not pretty" territory now, I still want those overhangs looking nicer. You can see the brim printed around the first layer to reduce curling/warping:

 

[procomsignathid]

Print #7 is a success! Seems to hold air pressure (very un-scientific "plug holes and blow into it" method), but good enough to test drill/tap etc. I'm still not satisfied with the overhang surface quality and the top of it is a bit rough too, but this is leagues better than prior prints, and without supports as well (which is how I designed the part). I'm doing more iterations to test overhang surface quality next, and I'm going to make some design tweaks to slim down the ridiculous wall thickness.

Lastly, I have a new build plate on order which will provide a smooth finish to the bottom of the separator. This may require PVA glue for bed adhesion, we'll see.

 

[procomsignathid]

Think I've got things nearly dialed-in. Working on the latest prototype now, about 7hrs left in that print.
The prior prototype had too many overhangs in the design, which is fine on the outside if you have supports, but not fine on the inside. I found that it was leading to a pretty raw interior surface finish, and would often lead to total print failures (the print head catching on a blob of nylon and knocking the print over), or poor air sealing. On the last run, I paused the print 3 different times to remove any nylon blobs, and the print finished successfully.

Even though it took some babysitting, it holds pressure! This is a huge milestone as 3D prints are not known for air-sealing. I've gotten here because of the filament type and the small layer-height / line widths, as well as how dense Im making it.

Been at 14.5 PSI all day today, still holding. Had one issue w/ the top port because I went too far w/ the tap, but that's an easy-to-fix skill issue in the future, for now teflon is holding it fine.

The next iteration has teardrop-shaped interior overhangs, which will remove the need to babysit the print and ensure solid layer adhesion.

I'm pretty excited! On the home stretch with these things now, soon I'll have a price cooked up.

Right now, its solid nylon-- I'm not doing any sparse infill, and I'm it's incredibly sturdy... I can probably skinny it down a bit and keep it bomb-proof while reducing the print time by a few hours.

 

[charliemeyer007]

Looking nice.

 

[ducktapeguy]

I had the privilege of trying out the new vapor separator from procomsignathid and it's a huge improvement over the hacked repair job of the old one I had. Dropped right in place of the old one without any issues and definitely feel a lot more robust that the OEM version. No more worrying about gas smell in the cab anymore.

 

[procomsignathid]

Glad to hear that @ducktapeguy! Funny thing is my old fuel vapor separator broke in the exact same spot.

Question for the masses... I now have models for early and late versions of this, the main difference being 2 mounting points versus 3 (see pics):

But I don't have good visual references for the fuel separator that was installed in the middle bench seat for some trucks, only the one that is mounted on the passenger side of the cabin behind the seat (next to to the fuel neck).

Does anyone have a reference for what the in-seat separator looks like? I'd like to model that one as well, and I plan to model the '80+ separators too.

I'm also planning on changing the hose barb style to match the OEM version more. The barbs are slightly shorter, but only have a single nipple and seal just fine / hold pressure with my testing. I decided to make the change after noticing that the more aggressive barb style was tearing up the test hoses I was using because it was so dififcult to remove. I have serviceability in-mind, and this part is in an awkward spot anyway.

I think the shorter barbs will reduce strain on the whole unit, especially considering one of the lower hoses curves to the side (and this is why I think that barb is typically the one that fails). Let me know what y'all think:

 

[CruiserTrash]

Glad to hear that @ducktapeguy! Funny thing is my old fuel vapor separator broke in the exact same spot.

Question for the masses... I now have models for early and late versions of this, the main difference being 2 mounting points versus 3 (see pics):
View attachment 4007680 View attachment 4007681

But I don't have good visual references for the fuel separator that was installed in the middle bench seat for some trucks, only the one that is mounted on the passenger side of the cabin behind the seat (next to to the fuel neck).

Does anyone have a reference for what the in-seat separator looks like? I'd like to model that one as well, and I plan to model the '80+ separators too.

I'm also planning on changing the hose barb style to match the OEM version more. The barbs are slightly shorter, but only have a single nipple and seal just fine / hold pressure with my testing. I decided to make the change after noticing that the more aggressive barb style was tearing up the test hoses I was using because it was so dififcult to remove. I have serviceability in-mind, and this part is in an awkward spot anyway.

I think the shorter barbs will reduce strain on the whole unit, especially considering one of the lower hoses curves to the side (and this is why I think that barb is typically the one that fails). Let me know what y'all think:

View attachment 4007695

Suggestion: Make the mounting holes universal. That might look like slotted holes. These may also be useful for 60 Series trucks, and if so you could make incorporate all the mounting options into a universal solution.

Easier manufacturing, wider reach. Just sayin'...

I'll be interested in seeing how these do long term. Every single 3D printed product I've bought has failed by cracking along layer lines - all kinds of different print materials, layer fineness, heat settings, etc. If they hold up, I might be in. I think the way forward long term is sending this to an injection or roto molding shop though. I'd keep the separate barbs though, it probably reduces failure rates versus the originals.

 

[procomsignathid]

With regards to universal fit, currently the 2-hole and 3-hole versions are compatible with each other. You could mount up a 2-hole version to a 3-hole setup and nobody would be the wiser unless you removed the cover. Similarly, you could mount up the 3-hole to a setup which uses a narrower cover, and either deal w. the fin sticking out or cut it off. The 80+ models appear to use the same bolt pattern as well, its just the internals are shifted. Again, if anyone has pics / reference for the in-seat vapor separator, I'd love to see some pics.

As for 3D-printing viability... So far so good, but it's hard to say what will happen in 40+ years with these things. I will say that I am doing everything I can front the CAD, to filament, to print settings to ensure its as reliable as I can make it. Thus far, they hold pressure, and I mean around 15 PSI for days on end (until I remove the setup and test the next one). The filament Im using is 100% PA12 nylon, no carbon fiber or glass fiber reinforcement. If you have a suggestion on a test rig to punish these things, I might consider it if its within my means.

 

[CruiserTrash]

With regards to universal fit, currently the 2-hole and 3-hole versions are compatible with each other. You could mount up a 2-hole version to a 3-hole setup and nobody would be the wiser unless you removed the cover. Similarly, you could mount up the 3-hole to a setup which uses a narrower cover, and either deal w. the fin sticking out or cut it off. The 80+ models appear to use the same bolt pattern as well, its just the internals are shifted. Again, if anyone has pics / reference for the in-seat vapor separator, I'd love to see some pics.

As for 3D-printing viability... So far so good, but it's hard to say what will happen in 40+ years with these things. I will say that I am doing everything I can front the CAD, to filament, to print settings to ensure its as reliable as I can make it. Thus far, they hold pressure, and I mean around 15 PSI for days on end (until I remove the setup and test the next one). The filament Im using is 100% PA12 nylon, no carbon fiber or glass fiber reinforcement. If you have a suggestion on a test rig to punish these things, I might consider it if its within my means.

I’m just thinking about my daily driver/wheeler/kids sports practice 60. It gets rode hard. Stuff breaks. I wonder if there’s some time of coating that could help bond or reinforce 3D printed parts. Seriously every single 3D piece I’ve tried breaks in 1-6 months.

I don’t think my 69 40 has a his piece … things were pretty basic back then.

 

[charliemeyer007]

No real experience with 3D printing. Nylon 12 is listed good for alcohol and gasoline. I'd bet a thin overwrap of fiberglass would prevent delamination from happening.

 

[Andrew S]

Two thumbs up for the single barb upgrade.

 

[ducktapeguy]

It's nice to know it can handle 15psi, but that's probably overkill. I did a test one time and I don't think these vapor separators ever see more than 0.2-0.3 psi, because the tank itself would probably blow up at 1psi.

The smooth hose fittings would be a nice upgrade, I had forgotten how hard it is to remove those hoses once they've been clamped for a while.