Mossys 3D Models

Paul

Your baton is safe, I've still got L plates on in comparison. I love the idea of measuring the parts, but sadly I don't have a set to measure. I did an initial print run this morning using craftsman and standard settings mistakenly I let Chitu auto support so there were a number of failures. A second properly supported run is scheduled for this evening when our Grand-daughter goes home, all of these are just proof of concept runs, the actual prints will use ABS like resin, of which I got 3 litres from the fat man in the sky!

I'm still struggling to see how the con rod doesn't hit the axle once each rotation, but I'm sure it will become obvious at some time.

 

Brian,

I realised that about 10 mins after the previous posting, but thanks for point out the obvious. Mossy what a dummy you can be.

 

Yesterday I fired up the first test print of the Joy's gear but 30 minutes from finishing I had a conversation with Rob about a technical bit I didn't understand, when he said "the LG components are for a J21". Silently I thought oh &^%$ and yep when I checked the GA oh vkguhjyt it was. The Class A's Joy gear is very different. This morning I decided to scrap everything and start again, actually the radius block was salvaged, it was drawn from the GA, everything else hit the bin. Erindoors spent the morning in bed after a bad night with a heavy cold, so I redrew everything else. It's much easier and quicker second time around, I have even got a first test print done with mixed results.

The offset cams are a disaster, the con rod doesn't fit between the cheeks - my failure to check the measurements.
Both the Correcting Link and the Pendulum Links have very thin legs (.5mm), these distorted very easily when removing them from the supports pre-curing.
Plan 1 print as is but cure before supports removed, see how it goes.
Plan 2 legs thickened to .75mm, print 2 sets, remove supports before cure for one, after for the other.

On the happy side, radius link, connecting links, con rods and big ends all printed correctly.

So hopefully a reprint of the changed part plus the other parts not yet printed to be done later today, Classic one step forward, two steps backwards, but such is life.

 

Andy,

First up I generally don't leave resin sat more than a day it goes in a bottle labelled used resin. In cold weather like now I almost always decant any left over resin in the used bottle. Before using it I thoroughly shake the resin and allow to settle for 5 mins or so. If extra resin is needed, it's added in and shaken before immersing in boiling water. Then boil a full kettle of water and immerse both the resin bottle and the build plate for at least 10 mins, often a bit longer, but 15 mins max. Logic being if one or the other is cold it will steal heat from the other increasing the chance of failures, better safe than sorry. Almost always if it's going to fail it does do laying down the skate, why, who knows.

All of which makes me sound like a saint, which I'm not, short cuts often occur and normally fail. All the failures from the first test were cause by human error and since I'm the human enough said.

 

Start of the experimental build.

I have printed 2 of each part of the Joys motion with a couple of obvious exceptions. All printed using Craftsman resin, the actual build, assuming everything works, will be done using the more resilient ABS resin.

Almost all the linkages etc are either .75mm or 1mm thick with the exception of the conrod and big end which are 1.5mm thick. Using LG logic, the male part of each linkage will be slimed down slightly and the .9mm hole broached out to be nominally over size, such that it moves freely on .9mm wire. The female legs open out sufficiently to take the .9mm wire push fitted. Rob and Paul have suggested using raw resin as the glue, cooked in my wash and cure machine or by a UV light pen. The build of the first set of motion I plan gluing using thick superglue and a paper gasket in the joint. The resin theory will be tested on the second set of motion.

Initial test will be concentrating on linking the correction link, connecting link, pendulum link and conrod, which should be enough for one day for my poor eyesight. Will it work, my thinking there’s a 40% chance of getting the first set working first go, but I am expecting some resin failures along the way, so a spare set will be printed alongside the build.

Success or failure more late.

 

Less than an hour in, all I have done is get everything organised that I might need and done a simple wire test. Not surprisingly a .9mm hole doesn't print at .9mm, .7mm fits easily with a bit of slop and I don't have any .8mm. I have decided to go with .7 for this set of motion and broached out ,9mm for the second. Going on do I try to locate some ,8mm wire or broach out the real set? Without Eileen's, I supposed a trip to the squires website might source .8mm if I go that way,

 

I've got more than fingers crossed Paul. Already busted one of the pendulum link legs, so the spares will come in handy when they finish printing. On the positive side correcting link, connecting link and con rod prep'd, now for the glue bit,

 

Cheers Rob. Two joints successfully made, now for the most difficult of the three. If that works then I need a next plan!

 

Next plan is to work out why the Pendulum Link doesn't fit over the Correcting link - they are both the size? Confused, very. I also had a play with the conrod fitting over the crank shaft - it doesn't. More investigations needed and just when everything was working out just fine and dandy.

The two successful joints were both prep'd the same way, the first was glued together using super glue and a paper gasket, the second using my UV light activated glue pen and a gasket. It seems to have worked but I'm still not convinced by it. So all in all two steps forward one backward, or some such.

 

Resolving the pendulum link problem was easy - print the right one - idiot! But fitting it to the correction link as the third hinge, what a proverbial %$£^%^, but it's done, which proves I can assemble the 3 links and conrod, some progress. As a work colleague once said to me "my learning curve is vertical" I've learned so much just doing a few simple joints. I have also test fitted the piston rod assembly and the valve rod assembly, both proved much easier than the pendulum link, phew.

As an experiment this morning I did the pendulum- correcting link first on some spare components - much easier and it didn't compromise fitting the the other two particularly.
With two of the joints I used a taper broach to ease out the holes to fit .9mm rod, but there is precious little resin left, so I am not happy with that solution. An obvious alternative is to buy some .8mm rod and use that, or reduce the holes to .8mm and use .7 instead. The second would produce significantly more resin around the hinges. Finally I bought some fine dress making pins which have a .55mm diameter, why not reduce the holes to say .6 and use them. I would welcome thoughts and recommendations from the platform one sages.

I'm out of spare bits so experiments have ceased for now, the next batch of bits will be printed used ASB resin after a decision is finalised on the hole size and therefore the rod diameter.

Mossy

 

In the dark hours this morning I imported my chassis to see how the motion fits relative to it and was worried as the screen grabs below show. As an antidote I drew a new chassis frame using the GA, again everything towers above the chassis, and it looks like my chassis is a bit to low. That all needs checking out but checking the GA yes it does extend above the frames. Also assuming the motion is in the correct place, it will significantly compromise the rear of my smokebox, so another thing to resolve, but if things were simple life would be boring.

My Chassis:


Redrawn using the GA:

 

As suggested by Rob I change the hole sizes on the three main links and the conrod to .65mm with the plan to used the .55mm pins.
Its the first time I have used the ABS like resin that I got for Christmas and having read a posting from Paul used the same Chitu settings as Craftsman with no failures. I suggested to Sarah to get a different colour to grey, oh what a mistake, she found a 3 for 2 offer and bought beige. Out of the bottle it's sort of pale orange, cooked, washed and cured it's an semi translucent off white colour, I suppose a bit like bleached bones. Since I have 3 litres of the stuff I am going to have to live with it.

Anyway more to the point a .65mm hole (which I knew would come out under sized) wouldn't take a .55mm pin. First test a .65mm drill, ok but there is side play which may or may not matter. Second test a .6mm drill which doesn't fit my pin drill so had to be used manually, much better, probably good enough. Final test a taper broach used carefully on both sides, possibly as good as the .6mm, but I would favour the .6mm drill.

Too late now to do more now, family due pretty soon, so the first assembly with pins will be tomorrow morning. All up an interesting excersie.