Reading a drawing - Radius

Ed I don't think that will work with the mating parts, did you just take the angle from bruce's drawing?

Centre of crank (light green) pivot to middle of the slot for the piston rod is 41mm.

Cylinder ctr line to top of cylinder 20mm

Cylinder top cover 3mm thick

41-23 = 18mm but the piston rod is slightly above ctr of the slot so say 17.5mm

Edited By JasonB on 21/04/2015 17:35:22

Hi Jason, yes just some assumptions based on what was visible.

Regards,
Ed.

Hence the wink Tony

I hadn't spotted the feet hidden at the top of the photo. It makes more sense when dimensioned as Jason's redrawing.

Having drawn out an engine myself I have to agree with Jason's comment let him without drawing errors cast the first stone...

Thank you all for your comments and assistance. Yes it is one of Julius' drawings and I am grateful for the detail (and lack of it). Because I was so focussed on the 2nd page I didn't think to go back to the first where the 142.5mm dimension is. That would have helped.

Thanks Jason for the alternative fixing idea. I think I will be going with that.

I had come up with 18.5mm by using the scale of some other dimensions so all your comments have been helpful in confirming that I am on the right track.

I will be sure to post some construction pics as I go along

Thanks again

Bruce

BTW - if anyone is interested in these drawings they can be found here

Edited By Bruce Edney on 21/04/2015 20:22:01

Appreciate I may be looking at this all wrong, but have looked at the drawing and believe the Rx dimensions are the ACTUAL dimensions ie R10 is 10 mm radius , R5 is 5 mm radius etc . For example , the lower right bend has an R5 internal radius , then because the material is 5 mm wide , this added to the radius = R10 .

Thanks Trevor

I get that but where is the centre point of the radius? That to me has been the confusing nit. I think Neil's comments are the way to go re using templates.

I think this forum and it's members are great. I know that there are many other forums for model engineers but I keep coming back to here. You guys are so helpful especially for a newbie

Bruce

Bruce, Taking the example quoted , set compasses or dividers to 5mm radius . place point on outer line of item and strike 2 radius's some distance apart . Join the 2 crests to give you a line running parallel to outer edge of item . Lightly draw a vertical extension to common edge on lower vertical part . Repeat exercise , but this time using a 10 mm radius . where the 2 new construction lines cross is the common centre for both arcs .

Trevor the propblem is that from the published drawing we don't know where the "outer line of item" is so you can't tell where to stick your dividers

Edited By JasonB on 21/04/2015 20:43:39

I missed the point here again so back to bed I think. There are however formula for bending on the net... Just google ( bending formula.)

At the expense of yet another edit: It's a pity the man didn't dimension the side elevation since scaling is a no no.

Edited By Jesse Hancock 1 on 22/04/2015 06:34:58

Edited By Jesse Hancock 1 on 22/04/2015 06:35:32

Edited By Jesse Hancock 1 on 22/04/2015 06:55:52

Well marking out and cutting version one was completely wonky. The old adage "Measure twice -cut once" comes to mind.

Second attempt involved (as somebody suggested) marking out on a thin piece of plastic and using that to centre punch all the centre points.

Then I marked it all out on the sheet.

Cutting out will need to wait until Friday

Bruce a tip for when you have to make two sheet metal items. Mark out one and clamp the second under it, drill say the top hole to a smaller 4mm and slip in a nut & bolt, drill one of the side 4mm holes and add another bolt then the last 4mm hole and bolt it up.

Now you can start cutting the parts and the two will come out exactly the same. The smaller internal radii can be done with a suitable drill bit rather than trying to file the radius. See the recent mention of filing buttons for the external radii. Finally open out the top hole to the correct 8mm

J

Thanks Jason

I hadn't thought of that pre cutting - only post - that will save heaps of time

This is why I love this forum!!!

Wish people wouldn't put "Closed" links into postings.

Have to be a "Member" to see them.

Regards Ian.

Then become a member - It free and has the same ethos as this group - open your mind to new things Ian

Edited By Bruce Edney on 22/04/2015 19:57:28

I think the man is talking about being a paid up subscription member Bruce. What I didn't like about the magazine subscription was the slow progress (real time) waiting for the next instalment of a highlighted project to move on.

It's for this reason I hope an electronic magazine is devised where you can play and replay parts of the action your not sure about. The parts where it's second nature to you you can skip.

However are there enough people out there willing to have a go at video recording what, how and when? If not costing the magazine (Disc) could get very tricky not to mention those who prefer paper.

Perhaps the way to go would be to run it concurrently with the paper variety but detached as far as content and costing are concerned.

No MEM is free to join, no different to just entering your e-mail just like this forum.

I'm sure that anyone who is actually interested in taking a closer look at Julius' drawings and the others that have kindly and freely be posted on MEM will be quite willing to join.

Its also generally a friendly forum with very little winging and mostly populated by members who get on and build models and like to share what they are doing with others.

As for video in an electronic magazine, Model Engine Builder went digital a while back, as you read the text you can click on any links that will take you straight to drawings, video, websites, etc

Edited By JasonB on 23/04/2015 08:26:34

Personally, as these are only cosmetic radii, I would have extended the straight lines to a point and then used a correct sized piece of rod/tubing to draw round after lining up with the straight lines.

Its easier to do than describe.