Mount Trapezium

[redhouseluv]

You really want it to scre wup tight just before it tightend on the arm so the plain length should be just over the 0.312"

Personally I would make it with a shoulder making the unthreaded section 0.156" for  alength of 0.314" and increase the hole in the arm to the same 0.156"

Is this what you mean? (see diagram). Sorry, I'm not sure what you mean by 'increase the hole in the arm to the same 0.156" ' - which hole OR do you mean the hole in the yoke when I make that?

[Jasonb]

That's it and yes increase the hole in the yoke but....

Thinking it over a bit more while having dinner there may be a better was as it is not easy to turn a small thread upto a shoulder.

If you make a second one exactly the same as the one you have already done so you have a pair with female threads. You can then make a separate "spacer tube" 1/8" ID x 5/32" OD and 0.314" long. Take a piece of threaded rod, screw it into one of the pair, slip on the spacer and then screw the other end onto the threaded rod and it can all be tightened up with just the right amount of space between the two faces.

[redhouseluv]

If you make a second one exactly the same as the one you have already done so you have a pair with female threads. You can then make a separate "spacer tube" 1/8" ID x 5/32" OD and 0.314" long. Take a piece of threaded rod, screw it into one of the pair, slip on the spacer and then screw the other end onto the threaded rod and it can all be tightened up with just the right amount of space between the two faces.

Yes! I like. that idea, briliant, thank you 

[redhouseluv]

That worked like an absolute charm! Thank you 

[redhouseluv]

Started the day off by making the guide blocks for the pivot pin I made yesterday when something didn't quite work out. They weren't going to fit in the vertical guides. It didn't take me long to get that sick feeling in the pit of my stomach when I realised what I'd done or in this case what I hadn't done.

The vertical guides were laser cut and the central slot was neither the correct width or length, I quite simply forgot  . I had the precarious job of widenning and lengthening them whilst they were bridged across a gap in the vice; I fully expected them to get chewed up and have to start again, but went a few thou at a time and got there in the end. The bottom of the slots are slightly longer than needed so I hope this doesn't effect anything?

That's it for today, before I make an error and hopefully I can finish the guide blocks tomorrow........

[crueby]

Good save!   

[redhouseluv]

Guide blocks are now fitting and slide up and down nicely, the bearing seems to be sitting centrally over the piston which is good. There seems to be a fair bit of lateral movement but I guess once the piston and conrods are connected that'll disappear?

[redhouseluv]

Time for yokes!

Before I started on this engine I did wonder about the making of the upper and lower yokes. Starting with the upper I need to make the 2 round ends and solder them onto the centre section, but I'm confused by:

1. The 0.625" measurement on the far right of the drawing - what and where is that or is that because I'm making 2 ends which are 0.312" each (i.e. 2 x 0.312")?

2. When it mentions wiring together before soldering, I presume I can just use single core electrical wire which won't melt and put it through the bolt hole of the end pieces and then tie it to the centre section?

3. The text has no mention of the radii in the drawing and suggests filing? Is there not a case for milling the larger radius using the mill and boring head or is this not feasible?

4. Why are the hole measurements given with 2 different sizes, 2.9mm and 3.1mm (in brackets)?

I have attached the text and the relevant pictures to give a better idea of what is required .......al thoughts and ideas appreciated, thank you!

[uuu]

I think the 0.625" is the overall height of the part - viewed end-on.  It's not very useful - unless it's to demonstrate that the part could be carved from a bar of that height.

Wilf

[redhouseluv]

Ah yes, could be, that would make sense.   

I'm also looking at the photos and comparing to the diagram and text. The text states mill the location slots for the ends, which are 0.312" but doesn't indicate a depth which is strange as that will impact the overall length of the piece. I guess I'll have to make both ends the same depth of slot and then modify the centre piece accordingly to get to the 2.312" measurement .......... not very clear this bit 

[Jasonb]

1 As Wilf says it is just the overall height and not critical

2 Soft steel wire is better if you have it, bit of garden wire with teh green coating removed or something like that.

3. If you photocopy (scan & Print) the page and draw a ctr line through each pair of holes they will meet somewhere off the top of the page, you can use that point to work out the radii and angles.

4.  2.9mm is 6ba clearance and 3.1 is M3 clearance

I'd be tempted to make the bosses overlength and with smaller holes or no holes and then work out teh radii and angles and mill the faces and drill the hole sto suit those.

[Jasonb]

If you can post what the marked length is I could draw it out to get the radii

[redhouseluv]

Thanks Jason

The height is 5.227"

I see what your saying about making the bosses overlength, I have drilled the milled the slots to a depth of 0.080", but no matter, if there's a better, more accurate way of doing it, all the better 

I did wonder about the angles too as it doesn't specify..

[uuu]

If the 5.506" radius and the 1.875" spacing are drawn up then the angle between the holes comes out at 19.97 degrees.

Wilf

[redhouseluv]

I get the 1.875" but where is 5.506" from?