Cat 1

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Looks good Dave - Upgraded model from mine..

Was the dual Z an option or did it come stock with that?

I can see you have the Creaity glass bed I think - That "sticky" side works well for PLA (for a while) but when you get to ABS/ASA temps it will Magically stop working (forever). The cure is to flip it over and print on the glass - Using a "sticky goo" as mentioned. Glue stick works great for PLA.. My goto for ABS is a mix of white glue, icing sugar and water. Odd mix but works well - I will find the data for you.

Cat 1

My Feedback: (1)

50 % white wood glue (UHU original white wood glue - water solvent)
50 % powder sugar (icing sugar)
Add droplets of water until you have a viscosity similiar to thin salad oil.

here is the mix - I apply with a little sponge - can be reactivated for a few prints which another wipe of the goo - it sticks well - let the print cool fully to help the release.

cleanup is by soaking in water for a minute and then scraping with a razor blade - at high ABS temps (90 deg C) it can turn brown which is normal - Washes off print with water though.

Raleighcopter

dual z was an upgrade. i think i paid $25 on amazon for it. i need to level the z and mark the couplers so i can tell if the two lead screws get out of sync (which could happen if the printer is off and someone messes with it). the other upgrades i got are a one piece extruder, filament out switch, upgraded bed springs, and cr touch sensor. i have a beaglebone black around here somewhere i may press into service running octoprint too.

thanks for the tech support so far. looking forward to squeexzing molten pla later today.

John_M_

5/16-32 Die


Wurth - Time serts are the only thread inserts that I have used other than a helicoil / recoil, and I don't like those as much as the threaded inserts... all the other brands only offer 1/4-20, 1/4-28... is it possible someone made their own insert?

Glowgeek

Thanks for the link John, I had no idea 5/16-32 was a standard! That changes everything. Makes it possible to fab my own insert using my wood lathe.

Just got off the phone with Time Fastener Inc. They have never made a 1/4-32 Bigsert. They also have never made an insert from brass either. Both of the ones used in this engine are made from brass. I'm thinking you're correct, someone fashioned the inserts themselves.

I will give it a shot, worth a try.

Raleighcopter

who wants to go boating?

Glowgeek

Cute Dave. Something to keep your rubber duckies company during bath time?

Cat 1

My Feedback: (1)

was that your first print Dave!!!! That’s awesome for this Early in. Wow!

Cat 1

My Feedback: (1)

if I can help in any way let me know. I’m a bit far away and cutting odd ball threads to have a good fit is a bit iffy without the recipient piece on hand - but don’t want to see you stuck with this fix.

Chris

Glowgeek

PM'd you Chris.

John_M_

Thats is interesting, they make a 1/4-32 time-sert in stainless, and in a copper plated alloy... specially for glow engine repairs mine you, and they never considered making one for their big-sert product line... I hope you made them think further about making one.

Brass is more durable than saito's base alloy, it also has very good thermal properties, helps to transfer heat away from these small spark plugs... not that these 1/4-32 plugs have much of a heat range to them... the ground electrode is so small, it will start to glow red hot with sustained rpm running too lean mixture, to the point it will run more like a glow plug rather than a spark plug, and actually continue to run on after you hit the ign kill switch.

Make a replacement in brass, red loc-tite it in place, and you'll have a robust repair, that should last a long time with proper care.

John_M_

That printed fairly fast... I take it, that is not the highest resolution... but its still came out pretty good.

Raleighcopter

i was a virgin up until today. i did spend time making sure the machine was square and the lead screws ran smoothly. aside from the z seam, i'm extremely happy, and i managed that using cura's generic PLA settings. i may need to lower the bed temp a bit too.

Raleighcopter

.2mm layers. Took about 100 minutes

John_M_

Not too shabby, a little too grainy for lost wax stuff, but great for all around project making.

Just think, in the year around 3000 something, you''ll buy something off of amazon, and instead of it being shipped to you, it will be sent to your very own personal "molecular replicator" where the resolution will be at the atomic level... It will happen.

Glowgeek

Thanks John.

I asked Time Fasteners why they didn't make a 1/4-32 Bigsert. They said that the standard Timeserts work so well that there wasn't a high enough demand to justify the tooling cost. They also claim that a properly installed standard insert should outlast the life expectancy of an engine. Makes sense, the torque requirement is very low on glow plugs and they are infrequently removed.

I will be forced to use hi temp/hi strength loctite to capture a custom fabricated brass insert because there will be no locking feature, other than tightening the shouldered insert into place. Will loctite survive the temps experienced at the spark plug? Hmmmm

Raleighcopter

Loctite 2620?

Glowgeek

High dollar stuff, rated 650°F. I've seen JB cold weld (450°f max) used on glow engine exhaust with satisfactory results but the temps with gas are higher.

New question, what temp is estimated at the plug threads? I have no clue, I just know that much of the heat (972°f-1472°f) at the plug tip is removed/sinked away by the surrounding material.

Raleighcopter

Consider that the threads closest to the inside of the cylinder will see temperatures significantly higher than at the outer surface. I suspect anything that holds at 450 f would be sufficient if you get it on a couple of the cooler end threads.

Glowgeek

Thanks. My thinking as well. In fact the insert will be made with a shoulder at the top, that area, and a thread or two down from it, will likely see temps closer to what is being measured by you telemetry guys. I'm guessing here Dave.

There's a darn good reason that Timeserts were made to mechanically lock instead of relying on threadlockers, me thinks.

1967brutus

Normally, just a touch hotter than the rest of the cylinderhead. My cylinder heads show on average some 300F all around, so maybe the threads go to 400F or therabout. Maybe a bit higher, but I would be amazed if it would hit 500F
The plug gets quite a bit hotter, especially at the centerelectrode, isolator nose and the protruding part of the mass electrode, but the threaded part of the plug has only slightly above head temperature.

Please don't take this as being pedantic, it is just to help you understand the matter: "Temperature" is not the same as "heat". The plug tip indeed gets very hot, but it contains very little energy, and the isolator nose quite literally is an isolator, not only for electricity, it also is way less conductive to heat than ordinary metals. That is why you can have a plug tip of around 1500F but 1/8" further down the road a thread temperature of only 400F

Glowgeek

Thanks fellas. I feel a bit more comfortable now.

1967brutus

That probably has more to do with the fact that combustion is an extremely chemically agressive process that has a tendency to creep into crevices. Look for example what happens to headgaskets if that protective metal ring at the hole for the cylinder bore gets damaged. The fibrous gasket material can obviously stand the temperatures, but not the chemical action of "burning".

Combustion under pressure really is a weird and agressive process. On the big marine diesels, that can easily achieve combustion pressures of 2200 psi or higher, and burn temperatures around 2700F, a good cylinder to liner seal can easily be achieved without a gasket. Yet, they all use a soft steel "burn ring" (official name, it is not called a gasket and also does not have sealing as main function) that has as main purpose to get squashed between head and liner and prevent crevices. Without that ring, the head and liner, that remain intact in the burnroom and the liner wall (exposed to the same pressure and temperature) will start to erode away at the landing face. Really weird phenomena.

Glowgeek

Is that what is called erosion corrosion?

1967brutus

In all fairness, I have no idea what that specific thing is called... it is not like the crevice corrosion associated with moisture, I know that much. It might have to do with hot gasses and pressure, but I really do not know the mechanism behind it. I only know that it happens.