Are existing designs good?

[Tins]

Been looking at the D1/2 headlamp retaining clips. I have printed many of them from a design found on Thingiverse, even posted some out to people. Printed them in PLA, PETG and ABS. They all fail. Driving me up the wall. Anyway, I got a genuine one yesterday. I compared it with one of my prints. The two are quite different. The wall thickness of the actual retaining cup is less, the slots for the expansion don't reach all the way down to the mounting plate. I think that my printing is not the culprit, but the design is. They always fail across the line marked by the bottom of the slots.
The original design from TV:
189119
My clumsy first attempt at a redesign: ( I already see a flaw, no taper to allow the ball to enter and push the prongs open)
189120
I have yet to test fit one, but will.

I know this is primitive stuff for a lot of you. I think though that my point is that just because a design already exists doesn't mean it's good. Doesn't mean mine is either😎. Still, if at first.....

[Tins]

Next try..

189130

[incisor]

does your printer run a heated chamber?

me thinks you would need to be printing abs at the higher end and in a heated chamber 60/80c to get the strength needed and to get decent service life out of them.

i did a few in asa and printed them hot and they seemed to wok okay but what they are like next time round is anyones guess

is an interesting project [thumbsupbig]

[Tins]

does your printer run a heated chamber?

me thinks you would need to be printing abs at the higher end and in a heated chamber 60/80c to get the strength needed and to get decent service life out of them.

i did a few in asa and printed them hot and they seemed to wok okay but what they are like next time round is anyones guess

is an interesting project [thumbsupbig]

Printer has an enclosed chamber. It is alleged that it can create those temps off the heat of the bed. I tend to cover it with a blanket when printing materials that need it. I haven't actually checked the temp inside.

[workingonit]

189120


I know this is primitive stuff for a lot of you.

Not at all primitive...sophisticated, given everything you have had to learn...people that don't appreciate what lies behind, ask 'couldn't it be a different colour?'.

It's hard to tell from the photo but are the vertical slots at 120 degree intervals? And why did you use red[bigrolf]

And I have a bone to pick with you. Why did you post that youtube clip of the 'green tractor' defender? I blame you for me spending many hours til the wee morning watching all the linked videos of that machine in action - 'it's Tin's fault' I tell my wife, not wanting to admit my own weakness. There was a walk around video on the machine showing all the modifications. Do you know if he was an AULRO member? Thanks again for the diversion.

[Tins]

It's hard to tell from the photo but are the vertical slots at 120 degree intervals? And why did you use red[bigrolf]

Yes, 120°. I tried to copy the genuine as best I could. As for red, Tinkercad chose that. I didn't know how to change it. The actual test prints are in a white plastic with a green tinge as they glow in the dark...... Wonder if I need to install the headlights at all.


And I have a bone to pick with you. Why did you post that youtube clip of the 'green tractor' defender? I blame you for me spending many hours til the wee morning watching all the linked videos of that machine in action - 'it's Tin's fault' I tell my wife, not wanting to admit my own weakness. There was a walk around video on the machine showing all the modifications. Do you know if he was an AULRO member? Thanks again for the diversion.

It's awesome, isn't it? I don't think he's AULRO. I actually contacted him re going out with them one day. He loved the idea of taking the OKA out. Course, I wouldn't want to show him up, so I suggested some mild tracks so he could keep up..[bigwhistle]

And, you can blame me, no worries. Everyone else does.

[workingonit]

...Tinkercad...

You must be proud they named the program after your online handle. I use FreeCAD.

How do you think an OKA really would perform in terrain tackled by the green tractor? Wonder why they never made a 'Little OKA'? From memory they're long leaf spring machines? You got any pics of your OKA on aulro? Wonder if anyone has ever put a 4BD1 powered drive train in one? Keeping it relevant to the thread, does the OKA require a lot of printed plastic parts [biggrin]

[Tins]

How do you think an OKA really would perform in terrain tackled by the green tractor? Wonder why they never made a 'Little OKA'? From memory they're long leaf spring machines? You got any pics of your OKA on aulro? Wonder if anyone has ever put a 4BD1 powered drive train in one? Keeping it relevant to the thread, does the OKA require a lot of printed plastic parts [biggrin]

When I had the 38" XVX tyres it would have gone a fair way on those tracks, but would probably have lost it on the articulation, which is nuts on that County. Yes, the springs are long ellipticals. They are amazing, and leave pretty much anything behind over corrugations. LLAMS fitted D3/4s excluded. Most conversions seem to be 6BT Cummins 12 valve. But that's difficult as everything is on the opposite side. Most of those run an Allison behind them. An easier conversion is to simply replace the 4 cyl Perky Phaser with a 6 cyl one. Almost the same power as the Cummins, and apart from engine mounts it's almost a straight bolt in job, except for the bellhousing. And they use a Bosch VE pump, so if you can fix a 300TDi... well..

Back to the topic... The more I go the more things I will find for the printer. It's partly why I'm fooling around with the headlight clips and have made a couple of other bits for my Disco.

Pics? (https://www.aulro.com/app/showgallery.php/cat/1470) If you can be bothered...

[V8Ian]

Would it be possible to print the plastic, gutter cover for D2s? Obviously not as a single piece, but in sections to be joined, in situ.
Incisor already prints the corners, for these cars.

[Tins]

Would it be possible to print the plastic, gutter cover for D2s? Obviously not as a single piece, but in sections to be joined, in situ.
Incisor already prints the corners, for these cars.

I also have the files for the corners, but I reckon Inc is the bloke for those. Thing is, on my current printer the sections would be about 250mm long...... Mike might do better if his grouped therapy commitments permit.

[V8Ian]

I've got Incisor's corners.

[workingonit]

Thought I was being creative referring to 'Little OKA', but seeing 'OKAPotamus' - I'm still laughing minutes later.

Printed plastic windscreen wiper shroud would be good for the D2 when it runs. I did wonder about a wooden form and hammer over thin aluminium or stainless.

My D2 has been parked up for a year while I ponder lifting the head. I walked into that world of pain they talk about if you take the exhaust manifold off to fix the whistle, and the studs break. Should have printed a wedge and pushed it between the head and manifold.

Replacing the exhaust gasket on the D1 was a breeze by comparison.

[Tins]

Thought I was being creative referring to 'Little OKA', but seeing 'OKAPotamus' - I'm still laughing minutes later.

You haven't seen it emerge from a mud wallow....


Printed plastic windscreen wiper shroud would be good for the D2 when it runs. I did wonder about a wooden form and hammer over thin aluminium or stainless.

Too many sections on my printer. I think I can just plastic weld or even JB weld mine. Except it's brittle, of course.


My D2 has been parked up for a year while I ponder lifting the head. I walked into that world of pain they talk about if you take the exhaust manifold off to fix the whistle, and the studs break. Should have printed a wedge and pushed it between the head and manifold.

Replacing the exhaust gasket on the D1 was a breeze by comparison.

Mine now has M10 bolts on the end holes. Head was not removed, but care is needed as you're getting a little close to the water jacket for any hamfistedness.

[cjc_td5]

Been looking at the D1/2 headlamp retaining clips. I have printed many of them from a design found on Thingiverse, even posted some out to people. Printed them in PLA, PETG and ABS. They all fail. Driving me up the wall. Anyway, I got a genuine one yesterday. I compared it with one of my prints. The two are quite different. The wall thickness of the actual retaining cup is less, the slots for the expansion don't reach all the way down to the mounting plate. I think that my printing is not the culprit, but the design is. They always fail across the line marked by the bottom of the slots.
The original design from TV:
189119
My clumsy first attempt at a redesign: ( I already see a flaw, no taper to allow the ball to enter and push the prongs open)
189120
I have yet to test fit one, but will.

I know this is primitive stuff for a lot of you. I think though that my point is that just because a design already exists doesn't mean it's good. Doesn't mean mine is either[emoji41]. Still, if at first.....Try to get some fillet radii on the bottom of the slots and where the tube attaches on to the base plate. Fillets over a few layers are much more stable. The change in shrinkage at hard edges are weak spots for layer failure.

C

[Tins]

Try to get some fillet radii on the bottom of the slots and where the tube attaches on to the base plate. Fillets over a few layers are much more stable. The change in shrinkage at hard edges are weak spots for layer failure.

C

Chris, can you expand a bit on that? I'm feeling my way here.

[cjc_td5]

Chris, can you expand a bit on that? I'm feeling my way here.

Hi Tins.
My apologies for not getting back to you earlier.

My previous post tried to make comment that angular edges can often develop stress concentrations and issues with adhesion of the layers. As the plastic cools after it is printed, often it shrinks, developing weaknesses at stress concentration points, which can become failure points when loaded. One way to avoid this is to design in some radii in to angular edges, so that the form shape transitions over a few layers.

189230

One spot that causes issues is the bottom of slots in the upper tube. You can see that I have placed some small radii fillets to remove the square edges in the bottoms of the slots? The join from the base plate to the cylinder is another obvious stress point, due to the different shrinkage between the two different sized components. I have placed a fillet around this join to transition from one shape to another.

Hope this helps.
Chris

[workingonit]

[QUOTE=cjc_td5;3219035]... design in some radii in to angular edges.../QUOTE]

Really great point...now I'll have to go back review a bit of my work.

[Tins]

Hi Tins.


189230



Hope this helps.
Chris

Yes. I thought you meant something along thise lines, but the pic clears it up beautifully. Thank you. The bottom of the slots is easy. I'll have to put my Tinking cap on for the other bit... Reckon I can see a way.

I'm glad I bought the printer now.