Tag: Repairs

If it used to work, it can work again

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

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

Recoil Starter Lube

This being leaf season, I just discovered that the recoil starter on the hulking 8 HP tangential leaf blower retracts very, very slowly. Having already started the engine, I did one pass around the yard with the pull cord dangling over the handlebar, but that’s not to be tolerated.

The starter mounts on the back of the motor with five screws, so removing it posed no problem at all. Removing the central screw released the friction clutch that helps extend the pawls, exposing the central boss that’s the combination hold-it-all-together point and gritty bearing for the rope spool:

Leaf blower recoil starter

Pulling the rope turns the spool and extends the pawls that engage the crankshaft. After the motor starts, the pawls retract and none of that stuff moves, so there are no high-speed bearings and not much need for strength.

I brushed off some of the larger chunks, worked machine oil around the central post, wiped off & lubed the pawls, took the friction clutch apart & lightly lubed it, put everything back together, and the starter now works fine again; there may be too little friction in the clutch, but that’s in the nature of fine tuning.

The leaf blower Came With The House™ and dates back to the era when Kohler made cast-iron engine blocks. It runs lean on the oxygenated fuel that’s mandated for Dutchess County these days, so it now runs lightly choked.

Tip: before you yank the rope on a small engine, pull it slowly until the crankshaft stops turning freely, then let the rope retract. That positions the piston at the start of the compression stroke with the valves closed, so your next full-strength yank will do the most good.

2013-11-16

HP Scope Probe Flange Repair

Quite some time ago I manage to break the finger flange on one of my scope probes and, what with it being made of an un-glueable engineering plastic, a simple repair job failed quickly. It’s entirely round and a perfect lathe project, but … this is easier:

You can see remnants of that failed repair just below the fracture:

HP scope probe flanges - repair disk — HP scope probe flanges – repair disk

Some epoxy around the rim of the flange, plus filling the missing sector, looks about as grubby as you’d expect:

HP Scope Probes - rear — HP Scope Probes – rear

That’s a tiny zit at about 1 o’clock which came off with fingernail pressure.

From the business end, it actually looks pretty snappy:

HP Scope Probes - front — HP Scope Probes – front

I’m mildly tempted to preemptively reinforce the other probes…

The OpenSCAD source code joins two parts with coincident faces, but it worked out OK for once:

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

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

ThreadThick = 0.25;
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,$fn=NumSides);			// main repair part
			cylinder(r1=(DiskOD - 2*ThreadWidth)/2,r2=DiskOD/2,h=2*ThreadThick,$fn=NumSides);
		}
		translate([0,0,(DiskThick - FlangeThick)])				// flange clearance
			PolyCyl(FlangeOD,2*FlangeThick,NumSides);
		translate([0,0,-DiskThick/2])
			PolyCyl(FlangeID,2*DiskThick,NumSides);
	}

2013-11-13

Arduino Pro Mini Knockoff: Solder FAIL
Although it’s not obvious, the two blue 2431 Ω resistors just above the toroid are a divider that scales the switched battery voltage (from the p-MOSFET on their left) by 50% and sends it to input A0 on the Arduino Pro Mini board:

Hall effect sensor – toroid CCW field

The firmware can use that input to dim the LEDs when the voltage drops below some preset threshold and, eventually, turn them off completely.

Figuring the actual battery voltage is straightforward:
- get 10 bit ADC value with analogRead()
- multiply by actual V_CC (measured at 4.96 V for this board)
- divide by actual voltage divider ratio (measured at 3.78/7.57)
Which, of course, reported the battery voltage was 4.116 V. Huh?

After spending far too much time poking the code with a sharp stick, I wired the divider to the (previously unused) A6 and A7 inputs and dumped the raw ADC counts for all three. The answer should be somewhere near 763, but the three values came out around 215, 667, and 750. Huh?

The A0 value is totally bogus, so I finally looked at the Arduino Pro Mini board:

Arduino Pro Mini clone – chip overview

Hmmm. It turns out A0 is the second pin back on the left side:

Arduino Pro Mini clone – unsoldered leads

Double hmmm. An even closer look:

Arduino Pro Mini clone – unsoldered A0 lead

Well, that was obvious after I figured out where to look…

I slathered flux on all the pins, touched each one with a soldering iron, and it’s all good.

This is a knockoff Arduino Pro Mini board from eBay, of course, and the rest of the boards in that lot were OK. Their QC inspection almost certainly boils down to running the Blink sketch: if the LED blinks after the power goes on, ship it!

Blink doesn’t verify the analog inputs, which turn out to be wrapped around that corner of the package.
2013-11-11
Kitchen Spatula Handle Anchoring

Shortly after we bought this kitchen scraper spatula (or whatever it’s called), the handle pulled out of the blade and left it sitting in a bowl of batter. That turned out to be unsurprising, given that neither side of the interface has any mechanical locking features. I rinsed the batter off, stuck some urethane glue inside, rammed the handle in place, and hoped for the best. Lacking any mechanical interlock and not bonding to either surface, the adhesive didn’t improve the situation.

So I recently added a pair of stainless 4-40 setscrews standing just proud of the handle’s surface that should dig into the blade and hold it in place:

Spatula handle enhancement

Another item for the shopping list…

2013-11-10
Samsung Quiet Jet Vacuum: Floor Brush Wheels

After rebuilding the front end of the Samsung vacuum’s floor brush, I’d hoped that was the end of it; other than replacing the brush strips every now and again, it’s been cooperative. Recently, however, one of the wheels popped off, which revealed the minimal mechanism holding them in place:

Samsung Quiet Jet – floor brush wheel interior

Those four delicate latches have worn themselves and the hub to the point where they ride over the edge at the slightest provocation. I pulled both wheels off and packed three turns of insulated wire (one turn is visible in the photo, as it was an iterative process) around the outside of the clips, with the intent of restoring enough force to hold the wheels in place until we exhaust the lifetime supply of bags I bought for the thing…

2013-11-09