Mossys 3D Models

Andy,

You wanted pic's so, not the greatest photos, but I don't have or need a macro to photograph birds, my 500mm works just fine. BTW it's a real 5p not Rob's extra large one just to fools us all.

First test build



Bottom left the connecting link, this normally fastens to the cylinder block and is free to rotate vertically about its right hinge.
It links to the Correcting Link, which itself links to the conrod and the pendulum link.
The pendulum link fits into a slide block and also links to the rod controlling the valve.

Todays task:



Lots of cleaning up to do first. The four components from the first test at the bottom.
In the middle far right the big end, far left the piston rod and part of its gear.
Top row right to left, the slide block which the pendulum link slides up and down in. The radius link, it connects to the top hole in the pendulum link and on its left to the valve control rod.

All these have had the hole size reduced to .65mm and will be fitted together using .55mm pins.

Assuming it all works the next thing to do is to create a test bed and start testing the link between the Joy motion the valve chest and the crankshaft (which will be 3d printed with dismountable axles and a crank handle to give it rotation). One one thing which seems to determine success or failure with Joy motion is where on the frames the slide bock is hinged. This I am really unclear about. Even if I can't get it to work properly it will make a pretty comprehensive dummy motion.

Happy New Year everyone.
Mossy

 

A morning of good and bad, but all up progress. Before Rob rolls his eyes yes I haven't filed off the pin heads this is just a test.
All the links etc assembled and first test fitting to the cylinder back plate.

Good new, pins are much easier to use than rod, the point guides the pin through multiple holes quite nicely. Good News the whole of the motion excluding the slide bar fitted together nicely and moves as per plan.

Bad news, there's still a problem better the crankshaft and con rod which needs investigation, it may well be I haven't printed a corrected part. When the piston and its carrier are mounted on the piston slide, they don't move due to a lack of clearance. Easily fixed and that's what test build are for.

When I next drill a set of links out the plan is to drill the male links .6mm as per this build but drill the female links .55mm to make the fitting tighter. Still to look at are the slide block, and building a test rig, but small steps are better than none.

The photo clearly show how badly a print a cylinder parallel to the build can be, again test mode, the actual piston and valve rods will be printed at 90 degrees to the build plate to ensure a prefect cylinder. The cost a probable 4 hr print run not a 35 minute print. All up a happy man, but no more play as another batch of family due soon.

 

Rob

Pin heads there's only one point where they get in the way that's where the pendulum link slides across the correcting link, that one has to be filed away.
As for the rest a thought I had was to partially file them down which leves a better glue surface, but then arrange then so all the pin heads are between to two sets of motion, i.e. one set being a mirror of the other.

I wasn't looking forward to cutting an axle that's beyond me, so tell me more about your illusionist trick please.

 

Rob,

I found your posting about cranks on your Princess thread posting 144. I almost got to the same place but omitted the obvious, my central space is solid, rather than of a diameter to accept an axle. I will follow your example - its a far better solution all I have to do is find some taper pins. The troops are back from fairy house spotting so I am now on granddaughter duty while the boss finishes off cooking tea. Thanks for point out a simple solution.

 

Morning all.
Rob I have tentatively drafted up what you suggested yesterday, would you just check out my logic please.

On the GA the centre points of the 2 axles of the cranked axle are 7.5mm apart meaning the conrod slides 15mm, all of which sounds a bit long so I opted for a slide of 12mm.
The axle with eccentrics, I calculated a standard Slaters 3/16 axle is 4.76mm, so the centre hole for the axle to slide in I made 5 mm. The eccentric about which the conrod rotates is 12mm. Is it better to link the collar to the axle with a taper pin or would a small nut and bolt suffice? Obviously any or all could easily be changed so the body to be mounted on the axle is:



I then modified the conrod as in the below, the inside diameter of the ring is 12.25mm just to to give a little tolerance. Final question what size bolts would you use to link the two sides of the collar my smallest is 12 BA so I may well need to order some smaller ones.

 

Cheers mate, obvious when you point it out. My offset is currently 2.5mm, I might look to increase it a little bit as almost all of that axle is as you suggest buries behind the side tank. The same applies to retaining the eccentrics they will be neatly hidden from view. I think I might commit myself to printing a test bed and having a play, that way I can judge if greater movement is need or no.

 

Andy

I have to admit to growing confidence this could work. A full up test with everything fitted to the test rig should prove it once and for all, all appendages are crossed.

 

Tut tut Rob, I'm a Yorkshireman like you, short arms long pockets why buy when you can draw and print this:



It fits neatly on here along with 3 of each small item, a slide bar, eccentrics and a cylinder and all at the cost of 25ml of resin and 2hr 5mins printing all that's missing is a motion bracket (not drawn yet) and the test rig.



Next to hit the printer is the test rig

 

I printed the test rig. this morning and since I don't have a spare bottle for used resin, I have been very parsimonious with the resin, the inevitable happened it ran out before the print finished but was still useable. After washing and curing it I realised what a c*&^% design it was, access would be awful and it would be near impossible to see if all the links were working properly not only that me homemade axle is 4mm diameter, its hole 5mm . So back to the drawing board with this the new design. The top rails are there for a purpose, Laurie Griffin details how to find the optimum pivot point for the slidebar which lies somewhere along this line without the rail finding the correct spot would be "problematic. To be printed tomorrow morning.

 

Paul

I don't think the Beige is a translucent resin it's just a weird colour, light orange in liquid form and the horrid colour you can see in the photos when cooked and cured. As a punt I remember a posting you made when you first tried using ABS like resin (grey I think) where you concluded same settings as craftsman, so I have gone with the same. I have done 6 print runs without any failures except the last and that was a failure of the brain.

 

Beginning of the fun and games. Late yesterday I made a change to the test rig, the original plan was to print the cylinder back plate as a part of the test rig, but thinking about it i figured it would be easier to install the joys gear into the cylinder back plate first those install that into the test rig. I cut two grooves into the sides of the rig and extended the width of the plate by the same amount. Its a nice tight fit and the idea will probably be extend over to the proper chassis.

This morning I built two sets of Joys motion and attached them to the eccentrics barrel, I also installed the locating links with a 14mm spacer into the test rig. So what you have in the photo starting bottom left are the test rig and connecting links, above that the cylinder back plate, to the right the dummy axle and below that the Joys motion. Now to try join everything together fingers crossed I have just started Rob's Princess firebox print 4 1/2 hours so plenty of play time.

 

Oops pressed go to soon. Photo won't load a security error! A couple of things came up during the build. There needs to be a little tolerance between the big end and eccentrics drum probably .25mm and also the channel that the conrod/big end needs really careful cleaning to ensure smooth running. The grey stuff that can be seen is a Rob suggestion, graphite from a HB pencil, it definitely makes for smoother running of the links at the cost of making inserting the pins more difficult.

 

A day of mixed results, yes all the components fitted neatly into the test rig but the axle wouldn't turn because everything was locked tight. Before throwing it in the bin I set Robs Princess gear printing. 5 hours plus they are done and being washed. Going back to the Joys test one of the links was causing the problems so I stripped everything back to the conrod and piston rod, everything started revolving, but the piston carrier fell off the slide bar, they need extending. I was also unhappy with the piston rod which wouldn't stay straight so I did a redesign to use brass rod for both the piston and valve rods, fortunately I have some 1.6 and 1mm brass rod kicking about which looked suitable. Sadly the changes to the slide bars have committed me to another 3 hour plus print run before I can progress things. Yes another day of 2 steps forward 1 back, but also lots of learning as well.