The Smell of Molten Projects in the Morning

Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.

Category: Machine Shop

Mechanical widgetry

Toyota Sienna Hood Rod Pivot

We don’t drive the van nearly often enough (*) to keep the battery charged in cold weather, so I use a trickle charger to keep it alive between jaunts. While opening the hood one evening, I managed to twist the plastic fitting that anchors the hood prop rod beyond its limits and snapped the poor thing off, which left me holding the hood in one hand and the rod in the other.

After extricating most of the fragments from under the van, I found that the OEM part had a hollow post that snapped into a square hole in the front bulkhead under the hood. The post had two keys and a pair of snap latches that held it in place, a design that seemed optimized for rapid assembly with no fiddly parts, but which depended on a few millimeters of plastic to restrain a meter of steel rod.

I made up a simple replacement with a solid square post and a square cap to clamp it against the bulkhead:

Toyota Sienna hood rod pivot – first version

The general idea is that the screw puts the entire post under compression, giving it less temptation to shear at the deck line when I twist the rod a bit too far out of line. That 8-32 screw seemed entirely adequate to the task; a 10-32 screw would take up too much of the post for my liking.

Alas, it turns out that underneath the bulkhead’s top flange lies a metal plate surrounding the headlight that’s so close to the hole that the big blocky cap wouldn’t fit. So I slimmed the cap down to three thread widths and tried again, only to discover that the plate came that close to the edge of square hole.

However, there was a gap between the bottom of the bulkhead and the top of the plate, so I introduced pivot and cap to Mr Belt Sander, removed enough plastic to let the cap slide into the gap, then discovered the 8-32 screw head was just slightly too large to let the screw align with the post.

Another tweak to the model, based on actual measurements on the abused parts, produced the final version:

Toyota Sienna Hood Rod Pivot – solid model

The rod hole has a nice bevel, there’s no fragile neck between the rod hole and the base flange, the solid post lies flat on the platform for EZ building, and there’s a slight offset between the post and the flange that eliminates the need for support material. Printing it lying down orients the filament paths around the hole and base, making the part stronger in the direction it needs the most strength.

I think the cap walls could be slightly thicker, but we’ll see how long the thing lasts…

A group photo of all the versions, lined up from left to right, shows the broken OEM part, the first blocky attempt, the slimmed-down and too-long version to the rear, the shorter version that actually fit, and a backup part for when that one breaks:

Toyota Sienna hood rod pivot versions

The sanded-down part held the hood open while I took that group picture. Here’s what it looks like under load:

Toyota Sienna hood rod pivot – in place

The scrawls on the bulkhead just in front of the pivot remind me of fluid levels, torques, and suchlike. The stud sticking out to the rear is a headlight aiming screw mounted in the plate that caused so much hassle; you’d think I’d have noticed it before starting this adventure, but noooo…

For what it’s worth, that’s rapid prototyping in action: three (and a half) iterations in quick succession, each getting closer to a goal that you (well, I) can’t quite define, but will recognize when it appears. Took about three hours over the course of two days.

I loves me my M2 3D printer…

(*) Indeed, the tires often take three miles to warm up their flat spots due to sitting in the garage for a week…

2013-12-06
Browning Hi-Power Magazine: Floor Plate Modification
The Browning Hi-Power magazine has two floor plates:
- the interior plate captures the spring and locates it properly inside the magazine case
- the exterior plate provides reaction force against the spring and locates the interior plate’s boss
Browning Hi-Power magazine – base plates

The interior plate has two critical features:
- the ramp on the front (to the right) that guides it over the edge of the exterior plate
- the boss that latches the exterior plate in place
If you remove the interior plate, you must somehow hold the spring in place while sliding the exterior plate in place, after which the spring is free to thrash around inside the magazine under recoil forces.

An important point: you can buy exterior floor plates from all the usual sources, but, as nearly as I can tell, nobody sells replacement interior floor plates and they’re not included in kits of replacement springs. If you don’t have an interior floor plate, you must fabricate one from scratch before you can use the magazine.

So one thought is to drill a hole in the middle of the boss:

Browning Hi-Power magazine – drilled floor plate

OK, that’s not quite centered, but it’ll suffice.

Wire-brush the coating around the inside of the boss to prepare it for brazing, then braze a nut onto the inside of the floor plate (which I haven’t done yet), and run a socket-head setscrew through it:

Browning Hi-Power magazine – drilled floor plate

If that threaded into a block loaded with steel-filled epoxy, it’d never come back out again. You could machine the head down to a flat disk that would fit through the existing hole in the exterior floor plate and not provide any gripping surface:

BHP floor plate screw – disk head

To be absolutely certain, you could file the entire socket head off flush with the boss, leaving no way to grip the screw.

If the block surrounds the nut on the floor plate with a generous helping of steel-filled epoxy, then there’s no way to twist the block off the plate.

If the block also captures the spring, then you can’t heat the plate enough to un-braze the nut without also de-tempering and wrecking the spring.

I can think of a few other ways to attack it, but none seem like a project that would readily convert the magazine into one holding a few more rounds. Opinions may differ, of course, but …
2013-12-05

HP Scope Probe Flange Repair: Improved Spares

While reducing the clutter atop the Electronics Workbench, I ran off four more probe flange reinforcements, just so I’m ready for the next crunch:

They’re almost identical to the previous version, although I tweaked the taper to end slightly inside the cylindrical cup, thereby eliminating the coincident faces and leaving a minute rim that doesn’t matter:

HP Scope Probe Flange Repair - bottom — HP Scope Probe Flange Repair – bottom

Given that I’ve had the ‘scope for nigh onto two decades and have only broken one probe flange, I think four reinforcements will be a lifetime supply: with any luck, the scope will blow a capacitor before I do.

The OpenSCAD source code:

// Tek Scope Probe Flange
// Ed Nisley KE4ZNU November 2013

//- Extrusion parameters must match reality!
//  Print with 2 shells and 3 solid layers

ThreadThick = 0.20;
ThreadWidth = 0.40;

HoleWindage = 0.2;

Protrusion = 0.1;            // make holes end cleanly

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

//----------------------
// Dimensions

FlangeOD = 16.0;
FlangeID = 8.75;
FlangeThick = IntegerMultiple(1.25,ThreadThick);

DiskOD = FlangeOD + 4*ThreadWidth;
DiskThick = FlangeThick + 4*ThreadThick;

NumSides = 8*4;

//----------------------
// Useful routines

module PolyCyl(Dia,Height,ForceSides=0) {            // based on nophead's polyholes

Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

FixDia = Dia / cos(180/Sides);

cylinder(r=(FixDia + HoleWindage)/2,
h=Height,
$fn=Sides);
}

module ShowPegGrid(Space = 10.0,Size = 1.0) {

Range = floor(50 / Space);

for (x=[-Range:Range])
for (y=[-Range:Range])
translate([x*Space,y*Space,Size/2])
%cube(Size,center=true);

}

//----------------------
// Build it

ShowPegGrid();

difference() {
union() {
translate([0,0,2*ThreadThick])
cylinder(r=DiskOD/2,h=DiskThick,$fn=NumSides);    // cylinder around flange

cylinder(r1=(DiskOD - 2*ThreadWidth)/2,                // flange reinforcing plate
r2=DiskOD/2,
h=(2*ThreadThick + Protrusion),
$fn=NumSides);
}
translate([0,0,(DiskThick - FlangeThick)])                // flange clearance
PolyCyl(FlangeOD,2*FlangeThick,NumSides);

translate([0,0,-DiskThick/2])                            // probe nose clearance
PolyCyl(FlangeID,2*DiskThick,NumSides);
}

2013-12-03

Marmorated Stink Bug Sighting

Late in the fall, Brown Marmorated Stink Bugs move indoors to spend the winter; they can infiltrate through the smallest of cracks and seem to show up unannounced in the strangest locations. This one magically appeared on my M2 printer while I was starting it up:

Brown Marmorated Stink Bug on M2 Printer

I unceremoniously flushed its contribution to the gene pool…

2013-11-30
Browning Hi-Power Magazine: Trigonometry
The Browning Hi-Power magazine case has a 12.5° forward angle with respect to the floor plates:

Browning Hi-Power magazine – components

The natural axes lie parallel and perpendicular to the case axis, which means dimensions parallel and perpendicular to the floor plates (horizontal & vertical, respectively) require a bit of trigonometry. This doodle sketches some of the key values, not all of which are hereby asserted to be correct:

Magazine angle doodles

Name the variables:
- Slant angle α
- Height H along magazine axis
- Length L perpendicular to H
Components of H:
- vertical = H cos α
- horizontal = H sin α
Components of L:
- vertical = L sin α
- horizontal = L cos α
Extreme point of the tilt at the edge, relative to center point on axis:
- vertical = (L/2) sin α
- horizontal= (L/2) cos α
Projection of top parallel to axis onto horizontal:
- L / cos α
I suppose one could set up functions for all that, but I tend to just hammer out the trig where it’s needed.
2013-11-29
Browning Hi-Power Magazine Dimensions
This is a standard 13 round magazine from a Browning Hi-Power 9 mm pistol:

Browning Hi-Power magazine – assembled

Disassembled to show its five components:

Browning Hi-Power magazine – components

The follower has 15.3 mm long pegs that taper from 8.75 mm to 7 mm, on 14.5 mm centers. The spring compresses down to a little longer than that with 13 rounds atop the follower:

Browning Hi-Power magazine – follower

The top of the follower has a rather complex shape (yes, that’s a crunch toward the front of the ridge):

Browning Hi-Power magazine – follower top

The front view shows more curves:

Browning Hi-Power magazine – follower front

Judging from the online pictures, BHP followers have taken on a wide variety of shapes over the decades, so I’d expect almost anything would work more-or-less well.

The inner floor plate attaches to the spring and has a 5 mm dia x 1 mm tall boss that matches the hole in the outer floor plate:

Browning Hi-Power magazine – base plates

The hole in the outer floor plate is a scant 5.4 mm, just slightly under the head size of a 3.0×0.5 mm socket head cap screw. The OEM Browning magazines have a centered boss, but some aftermarket magazines move it a millimeter or so to the front or rear. The outer plate seems hard enough to be just about spring steel.

A tab on the front of the inner floor plate (to the left in this picture captures the spring:

Browning Hi-Power magazine – spring inside base plate

The inner plate is 0.75 mm mild steel and may be removable, depending on how tightly the tab got crunched during manufacturing. The tab extends a millimeter or so beyond the spring on the inside of the curve and is about 2 mm tall at that point.

The boss on the inner plate and the hole on the outer plate locate the spring at the proper position and also ensure the outer plate doesn’t accidentally slide off; you must push the boss inward to release the outer plate before sliding it forward. Using a rounded rod lets you push the inner plate far enough inward to release the spring pressure on the outer plate, making it much easier to slide; in fact, for my fingers, I can’t move the outer plate without inserting a rod in the hole.

The case is a seamless 0.7 mm thick high-carbon-steel tube with complex curves:

Browning Hi-Power magazine – case on grid paper

The “high carbon” part means that it’s not in the least bendy; a few operations on large presses mashed it into that shape and it’s not going to take on anything else by accident. The feed lips on the top can get bent if you abuse the thing, but that’s about it.

The case is 20.5 x 31.7 mm from the base to the latch hole, 99 mm long in front and 109 mm long in the back. The latch hole is 4.2 x 7.3 mm with a 2.7 mm notch in the front side, 67.2 mm from the base and 27.7 mm from the top. The angle of the case axis with respect to the bottom (on the right) is 12.5°.

Inside measurements at the base: 30.5 x 18.7 mm. The rear corners are essentially right angles and the front curves fit 1/4 inch = 6.3 mm or 9/32 inch = 7.1 mm drills.

The lower flutes are 26 x 6.5 mm, centered on the side (even though it doesn’t look that way), and compress the outside of the case to 16.2 mm and the inside to 14.7 mm. The tabs engaging the outer floor plate are 23 mm edge-to-edge, 10.5 mm and 6.0 mm long, and protrude 1.5 mm from the outside of the case:

Browning Hi-Power magazine – bottom

The top of the case is 10.5 mm wide at the rear of the feed lips, with the sharp bend 17.0 mm from the outside of the rear face:

Browning Hi-Power magazine – top

The spring is 1.25 mm = 49 mil wire, 143 mm flat-to-flat high, about 15.1 mm turn-to-turn, 13/32 inch = 10.3 mm ID at the ends, 13.2 mm outside width, 25 mm inside length, and 27 mm outside length. Those don’t quite add up, but the whole thing is, well, springy.

The spring exerts these crudely measured forces:
- 1 round = 1.1 kg
- 10 rounds = 2.5 kg
The follower moves 5.3 mm, so the spring constant is very roughly 0.26 kg/mm = 14.8 pound/inch. Aftermarket springs tout their stiffness and come in 5% increments of additional force, so that’s probably not a critical number.

Limiting the capacity of a magazine so that it cannot be “readily” converted back to a higher capacity seems difficult, particularly if you allow disassembling the magazine for proper cleaning and maintenance. If operator safety and proper function isn’t a concern, then many things become possible.
2013-11-28
PVC Cement Can Lid Griptivity Improvement

I’ve been doing a lot of fiddly gluing lately and, despite my best efforts, some adhesive collects in the lid’s screw threads. The gummy residue makes it really hard to unscrew the lid without a strap wrench after a few days.

Wrapping two turns of silicone tape around the cap helps tremendously:

Silicone tape on PVC cement can lid

It’s obvious in retrospect, is all I can say…

2013-11-27