PIII Schwingarm

[Brian Leach]

I have been attempting to cast Aluminum Schwingarms for the PIII.

I thought I would boor you all with my attempts so far

These are my first attempts at making patterns using pictures and a PII arm graciously sent to me by Mark and Gill



This was the first arm I cast. Not too bad, but obviously wrong.
I needed more information.




After much searching I found the information I needed and created SolidWorks model of what I think the Schwingarm may look like.
The center to center dimension is the same as supplied by ArmorTek.



This was cleaned up and midified a bit. I than cast that a few times
Unfortunately it was not easy going.

Here is a picture of one of the castings. I was having trouble with debris washing up into the detail



I also had sink holes from slowing up on the pour



Well, this is close to where I am now. I expect I will have updates in the next few days.

Brian

[Jim Fowler]

WOW!

Oh, I am jealous! You get the "Gold Star"!

If you end up with an extra set.......

Regardless, EXCELLENT WORK! Please keep us posted.

[Adrian Harris]

That's simply outstanding Brian

The Solidworks arm looks spot on to me.

Good luck with the casting technique - what are you using to make the molds ?

Adrian.

[Brian Leach]

Good Morning Gentlemen

and

Thanks.

I am using Petrobond an oil based sand. It makes really good molds, picks up the detail well and is easy to use.

I am making a plaster mold now for my spin caster to see how that works out. that will be another day or two.

Cheers!

[Tim Bowman]

Hi Brian

OUTSTANDING! Hopefully you will have these available by the time my Stug III project begins?

Very nice.

Keep up the great work
Kind regards
Tim

[Brian Leach]

Hello again,

Well, tonight my buddy Gorden and I had a couple of beers and decided to do a static test on one of the arms I cast. ( beer, power tools, cast aluminum what else do you do Friday nights!)

We chose the worst arm I had cast so far



This was after cleaning up the piece on the mill than drilling and tapping the arm



Well, it was the worst looking arm...

This picture shows how deep the bolt penitrates the arm



We than began to load it up


25lbs



50lbs



75Lbs This was the one with the sink holes!



100 lbs!





I have to tell you, it was SCARY! Weights, beer, running shoes...I have been told my toe will be fine in a couple of weeks... It has now been three hours and they are hanging there, so I think these might be pretty strong.

Initially I wanted run the test to failure, but I , I , these are my first arms, I worked so long on them, I just couldn't destroy it.

the PIIIs weigh less than 300lbs, twelve arms, about 25 lbs static pressure per arm.

I hope you have had a good night...

Sarah, does this answer your questions?

More to come...

Brian

[Adrian Harris]

Scary stuff indeed Brian

It does look like you've got just about enough strength there

> I just couldn't destroy it.

The good thing is though, with a bit of heat, it could be reborn

Adrian.

[Sarah Frazer]

Hi Brian,

I'm very pleased for you, even with the void the arm seems strong enough. A good mechanical test and beer sounds a happy combination

It would be a good test to drill/tap a vertical hole, where the suspension unit lower link goes and try it again. With a significant section missing, which would take most of the tension/compression forces, I doubt if it would survive your impressive static testing rig

The white masters which you used to make the moulds from look very good, are they from a 3D printer?

Looking forward to more of your casting and testing.


Regards,

Sarah

[Brian Leach]

Hello Everyone,

I have been working on my castings and thought an update may be fun

And Adrian, Yes I could recycle it, but I think it will go into my museum of failures and misfits (The box is getting kinda full )

I have been trying different methods of casting these pieces. Some of the failures were kind of subtle, others quite obvious

This was a problem of too much gas (small amount of water in the plaster mold. Question: what was the orientation?)



I have finally figured out the way to do the castings reliably with the help of Roland Mann (Thank You!)



These are the crude castings. I expect I will mill them this weekend.

Thanks for watching

Brian

[Brian Leach]

Good Day all!

This weekend I made-up a jig to hold the Schwingarms for machining.



This is an arm in the jig. As you can see, I wanted to be sure the arm didn't move while being milled.



It took me a while to machine the first arm. This is the arm beside an ArmorTek arm. The disk is the "plate" at the torsion bar end of the arm.




As you can see, the arm does not have the "plate" at the torsion bar end. These are cast seperately and will be slip-fit over the end.



I hope to make more of the Schwingarms this week, but I am going to have some wisdom teeth and two metal plates (ooch!) removed from my mouth Wednesday, so there may be some delay.

If you are interested in a set send me a pm.

Thanks for watching,

Brian

[Brian Leach]

Sarah,

I kind of goofed one of the arms, so did another, more scientific, static test with it ( I drilled the hole slightly off center).

I hope this answers any questions

The arm is pretty much standard for what I am offering.

I didn't clean this one up too much. Actually, beside milling the faces and tapping the holes I will be leaving the join line flash on the pieces so people can file them down to their preferences. it seems there were varying levels of "clean-up" on the join lines on the 1:1. This way there will be a bit of variability, character in the pieces.

This is the arm I tested. I took this picture after doing the test



This is at 110lbs



Here we are at 130Lbs



I tried 140lbs, but the wire kept unbending allowing the weights to fall to the ground before I could take the picture. I decided I prefer my toes as they are and gave up. It did hold for five or ten seconds before falling.

Cheers everyone, out to dinner!

Brian

[Brian Leach]

Hello Lady and Gentelmen!

So, here I am in the pub, an ale, a burger and, as you from the continet call them, chips, working away on the computer with people 9000 miles away. Hummm! Kind of amazing. But what I really find amazing is that I am just about mastering a process first done 3000-4000 years ago.

Charcoal, sand, a hair dryer, a few bricks, the remmenents of an old cylinderhead and I have what could pass as a tank part. Isn't life wonderful (not to mention the cold malt beverage God has bestowed on all who are worthy!)

Today I cast the last of the Anhangerkupplungen for a while. I had the pattern for what I was hoping would be the final version of the Schwingarm ready so I threw that in too. I think it came out pretty good, a couple of defects, but they will be taken care of with a couple of vents. I am happy, I hope you will be too. I am going to begin making these next week (Adrian) for real unless my girlfriend kicks me out (sometimes she has no sense of humor, like now, she is hitting me!). Then it may be two weeks.

PLEASE, comments, obversations send them to me, I may be lonely soon! (ouch!)

Here are a couple of pictures, cheers! Brian

[Adrian Harris]

Blimey Brian - you've certainly come a long way since that first piece that appeared in April

Looks superb to me - I love the surface texture and cast seam - they look spot on to me

Adrian.

[Brian Leach]

Adrian,

Thank you, that means a lot

It has been kind of a long haul.

I sometimes hope that it has been a bit entertaining too....

Best regatds,
Brian

[David Makaras]

These are my first attempts at making patterns using pictures and a PII arm graciously sent to me by Mark and Gill

Brian

Hi Brian,

Fascinating to see how things are done. Thanks for the pics.

The other thing I noticed is that Gill and Mark are now working on the PII.
Not sure why they sent you a PII arm rather than a PIII though.