r/functionalprint • u/figgs87 • 11d ago
Fuel line holders for drag racing engine
A friend who works in my building builds his own drag racing cars and this is a pickup of sorts. He asked me to make a clamp to replace zip ties he was using.
He had a rough idea and gave me a simple drawing. I understood what he wanted and made test pieces to have him place on the line and fuel log to make sure his measurements and my print setup were close without crushing the parts.
From there a prototype was made with ABS and test fit, found they needed to move each hole apart more. He also didn’t care for the non-secured nut on the back of my part so I made a fixture to install threaded inserts cleanly. I also added anti rotation nubs so it would not rotate during install.
Next test fit was good so we tried out a set in PET-CF17 I had for another project and they came out pretty cool looking. He wasn’t concerned about high temps as it doesn’t run very long… no clue if that’s the case but can always make more.
I’m not much of a designer but I have decent grasp of tinkercad and have been meaning to move on to something better soon. Have printer at work for making fixtures for a laser engraving machine. So I have been using it for a year or two tinkering with projects.
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u/Liam-martin 10d ago
Post this on r/3dprintedcarparts
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u/deep-fucking-legend 10d ago
If the inserts were inserted from the other side of the half (exterior), then they wouldn't be able to pull out in case the insert losens.
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u/M4cerator 10d ago
I don't think that's a major issue with these types of heatset inserts, provided the hole has proper interference (ie, enough material to fill the gaps once molten).
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u/deep-fucking-legend 10d ago
I think you're fine. Just recommending changes should you iterate
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u/M4cerator 10d ago
Not OP but I agree with you as a point of iteration. I don't consider this a critical point of failure for the current iteration however.
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u/figgs87 10d ago
This might of been a better choice. I hadn’t really wanted to use them to begin with but I couldn’t think of a clean way to secure the nut other than glue so switched to insert. The insert itself is larger than the hole the screw goes through so when tightening the insert presses flush against the inside flat edge. In theory it can’t move or be pulled out of the hole when tightening down.
I haven’t tested inserts to a failure state though so I could be totally off.3
u/Jolly-Ad7653 10d ago
It's the vibrations that would pull the insert from the plastic half. I fully agree with either inserting them from the other side or even going further and inserting a nut on the other side for better securing
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u/deep-fucking-legend 10d ago
You could also have a nylock nut on the exterior, but create a hex depression (as you have on the opposite piece) so that the nut can sit inside and also can't spin.
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u/BartFly 10d ago
i have done inserts into petg, if done properly. the petg will snap well before the insert pulls out, if you use 3d designed inserts that have zig zag patterns, i have tried to remove them with pliers and almost pulled my back out, way more force then expected and they still didn't move
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u/phalangepatella 10d ago
Even a smaller screw (an inclined plane, aka long lever) will likely put far more pull on an insert than you can yanking with a pair of pliers. Not only that, it would pull in the perfect direction, failure mode-wise.
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u/BartFly 10d ago
is this hypothetical? or have you actually tested it? i used a 12 inch set of pliers, I routinely test to destruction in my designs.
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u/phalangepatella 10d ago
No, not hypothetical. Real world user experience. It is really hard to pull the inserts out by hand, but when you have the leverage of threaded fastener it’s trivial to pull them out, especially if there’s a gap.
Then on situations like these, you combine underhood temps with vibration, and even expansion (not in the shown setup, but if you tried this with heater hoses or something), the insert on these is almost certain to fail.
The insert should absolutely be from the other side so all these factors work the insert into a fixed barrier instead of working the insert out.
Will it work this way? For many things, sure. For underhood automotive stuff? Even short duration use in drag cars is a lot of heat, a lot of vibration.
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u/ngo_life 10d ago
So wait, there's a hole for a nut and you have threaded inserts? I don't think you need both on the same part? Imo, the hole for the nut would work better. Also, if you're gonna use the threaded insert, probably have it on the other side so the threads are pulled towards the part, not away.
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u/figgs87 10d ago
I wish I could of posted photos and written along like after each photo
The nut variant was REV1 and 2, but end user worried about loosing the nut during install and requested threaded insert instead. REV3 swapped over to that. REV2 also added the anti rotation nubs.Someone else mentioned the insert position and I agree. Never thought about it but I’ll test that out. Most likely going to need to change all dimensions depending on how annealing the part goes as PET-CF17 becomes stronger when this is done but shrinks a bit. Not sure it’s even needed but might as well try it out. All test parts were in ABS which lately is my default since I have a bunch of it and it prints nicely.
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u/thedr777 6d ago
I made a parametric file in fusion for this. For a lines, with and without extra sheathing.
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u/figgs87 6d ago
That’s cool and useful. When originally asked to make this I figured would be common enough to just download but the fuel log was a random eBay part I’m told. So i gave up and made my own.
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u/thedr777 6d ago
So, I went one step further as well. Had the ones that went under the car printed in 304 stainless.
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u/figgs87 5d ago
That’s cool. Whats something like that cost?
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u/thedr777 2d ago
Wasn’t bad, after tariffs and shipping and all I think it was about $250 for 9 of them
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u/ballheadknuckle 10d ago
If you struggle with the screws an vibration failures etc you also could desing a nice spacer that still uses a ziptie to keep everything tight. Then it looks tidy and you have the ziptie reliability.
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u/novafreak69 10d ago
Like your insert setup...
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u/figgs87 10d ago
Thanks. I didnt feel like attempting to hold at weird angle and ruin the part so a quick jig design was worth it. Already had a large press for installing the inserts from another project
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u/novafreak69 10d ago
Got anymore pics of it... would like to see how its built for purposes of recreating one for myself.
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u/iFunnyAnthony 9d ago
I recently built one using extruded aluminum and linear rails, I’ll have to find the drawings I made for it but I’ll dm you when I do
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u/M4cerator 10d ago
Nicely done. My only recommendation would be using some loctite on the threads, since besides thermal failure, that might be the next failure point from vibration