Potty Overcrank 4415

[JasonBModerator @jasonb]

[JasonBModerator @jasonb]

Couple of things that don’t look right on the ME drawings when compared to the originals.

 

Fig 19 Crankshaft Bearings, the 5mm dimensions are shown but not the machined square flat they refer to.

 

Part 42 Eccentric Sheaves, Shown with 10mm bore as original drawings but crankshaft is shown as 12mm dia

 

Part 21 Outer Guide bar bearing, size of holes not shown

 

Part 23 Crankshaft, No length for the reduced dia and or unreduced dia at each end shown. Probably better to show the length of the bearing surface.

 

J

 

Edited By JasonB on 20/10/2011 19:41:28

Edited By JasonB on 20/10/2011 19:53:57

[Terry LaneParticipant @terrylane]

“Part 42 Eccentric Sheaves, Shown with 10mm bore as original drawings but crankshaft is shown as 12mm dia”

Hmmmm ….. a ‘tight press fit’?

[Stewart HartParticipant @stewarthart90345]

I’ll put my hand up to part 42:- 10mm bore 12mm shaft, I changed the crank shaft to 12mm but didn’t catch everything this impacted on.

 

The others are different than my drawing ?.

 

Stew

 

 

[Stewart HartParticipant @stewarthart90345]

Part 18 Bearing Cap M4 thread missing

 

Part 20 Oiler M4 Thread Missing

 

I’ve checked my original drawing out and they are correct.

 

For some reason the graphic artist insists on putting the diameter symbol in even where it isn’t required, they are probably not conversant with engineering drawing practice.

 

Don’t know what process they go through for publishing but I guess they copy them over then because they have reduced the size add larger text, but this isn’t done as diligently as could be. If I submit another article I’ll probably use a bigger font size this will reduce the opportunity for error.

 

Perhaps David would like to comment on this.

 

Any one wanting a PDF copy of my original drawing, just send me a PM and I’ll be happy to provide them.

 

Stew

 

[JasonBModerator @jasonb]

Part 19 on your drawing shows a 5mmx5mm flat machined on the top of the bearing, I assume the oiler bears against this to stop rotation. In ME the two 5mm dimensions are given but the square is not shown.

 

Part 21 I think is different anyway but the 4 holes are not sized

 

Part 23 Can’t find a pdf for that but it could do with teh added dimension.

 

Also on the big end caps one view shows a central 3mm hole but its not shown from the opposite end or as hidden detail from the side. Is this meant to be the dowel hole in the conrod?

 

Oh and the wrong photo has been used in pic 43.

 

While I’m on it reads as though you bore the bigend hole in the conrod and then saw off the cap, is that correct as I’ve always split the part first before boring as that way there is no risk od squashing the bearing when tightening the bigend.

 

J

[Stewart HartParticipant @stewarthart90345]

Jason

 

Thanks for the input, it gives people the chance to get things right if they are intending building this engine ther’s nothing worse than starting off on a project and being led up the garden path by a dodgy drawing.

 

Q1:- Part 19 on your drawing shows a 5mmx5mm flat machined on the top of the bearing, I assume the oiler bears against this to stop rotation. In ME the two 5mm dimensions are given but the square is not shown.

 

A1:- Part 19 are the crank shaft bearing, they don’t have this flat. The split big end bearing has this flat. don’t know why this is shown on part 19 its not on the origonal.

 

Q2:- Part 21 I think is different anyway but the 4 holes are not sized

A2:- They should be M 2.5 again they are on the original

 

Q3:- Part 23 Can’t find a pdf for that but it could do with teh added dimension.

 

A3:- I left the size off on purpose as it will depend on the size of the flywheel fitted.

 

Q4:- Also on the big end caps one view shows a central 3mm hole but its not shown from the opposite end or as hidden detail from the side. Is this meant to be the dowel hole in the conrod?

 

A4:- That could be me, its an optional oil hole.

 

Oh and the wrong photo has been used in pic 43.

 

Yes I noticed that

 

While I’m on it reads as though you bore the bigend hole in the conrod and then saw off the cap, is that correct as I’ve always split the part first before boring as that way there is no risk od squashing the bearing when tightening the bigend.

 

That will become clear in the next part.

 

Stew00

[JasonBModerator @jasonb]

A1:- Part 19 are the crank shaft bearing, they don’t have this flat. The split big end bearing has this flat. don’t know why this is shown on part 19 its not on the origonal.

 

This is the part, shows flats, the ME one has the 5mm dims but no flat

 

Don’t know why you say the big end bearings have flats, would have thought they just needed a hole for the dowel pin but will wait for the next issue.

 

J

[Stewart HartParticipant @stewarthart90345]

Quote:- Don’t know why you say the big end bearings have flats, would have thought they just needed a hole for the dowel pin but will wait for the next issue.

Quaote:-

 

Reply:- It acts like a key to stop the bearing turning, we use to have some Taylor and Challen draw presses that used this system on the main crank shaft bearings, so I used the method her.

 

Stew

 

 

[JasonBModerator @jasonb]

Ah are you saying the dowel pin bears against the flat to stop the bearing rotating? I can see that working.

 

Though I have usually seen a hole in the bearing to take a fixed pin or if the hole is at the top then the wick tube from the oiler is taken through the cap and into this hole so preventing the bearing from turning.

 

J

[Stewart HartParticipant @stewarthart90345]

Thats correct.

 

I’ve seen the other methods also, don’t know what advantage the flat on the bearing would have i just remembered it and decided to use it.

 

Taylor and Challen didn’t use it on all their presses, we had about ten of this type and they were all the same.

 

Stew

[Grahame Chambers 2Participant @grahamechambers2]

Posted by Stewart Hart on 21/10/2011 07:23:36:

Part 18 Bearing Cap M4 thread missing

 

Part 20 Oiler M4 Thread Missing

 

I’ve checked my original drawing out and they are correct.

 

For some reason the graphic artist insists on putting the diameter symbol in even where it isn’t required, they are probably not conversant with engineering drawing practice.

 

Don’t know what process they go through for publishing but I guess they copy them over then because they have reduced the size add larger text, but this isn’t done as diligently as could be. If I submit another article I’ll probably use a bigger font size this will reduce the opportunity for error.

 

Perhaps David would like to comment on this.

 

Any one wanting a PDF copy of my original drawing, just send me a PM and I’ll be happy to provide them.

 

Stew

 

 

Speaking as the illustrator for ME & MEW:

 

Part 18 – The PDF I was supplied with doesn’t show the M4 thread.

 

Part 20 – The same as above.

 

If a part is round I add a diameter symbol – if that’s strictly incorrect for engineering I apologize.

 

When I receive the PDF’s (or DWG/DXF etc.) they’re opened in Adobe Illustrator, I resize the diagrams to suit the magazine layout, adjust line weights & change the font to make them uniform throughout the magazine. The diagrams then go to David to check, if he gives me any corrections I change what’s needed, & then they go to the magazine designer.

 

I’m not an engineer & I’m not a draughtsman, I’m an illustrator. I also don’t work exclusively for ME or MEW, so with the time available & what’s supplied to me I hope only the smallest number of errors make it to print.

 

Thanks

Grahame

[Stewart HartParticipant @stewarthart90345]

Hi Grahame thanks for your reply.

 

I just wanted to understand a little of the processes an article goes through to appear in the magazine, I have no experience or knowledge of publishing, but from my time in industry I learnt that having some appreciation and understanding of what processes your product goes through will help improve the quality of your product, if I do submit any more articles I now have a better understanding to try and improve on them.

 

I will cheerfully put my hand up and admit that my drawings are not the best or the most accurate, like you I’m not a trained draughtsman, and I tought myself how to use cad, I just try and do the best I can, and try and spread the word about and encourage engineering.

 

Please don’t take any of this as a criticism, for me every one at the magazine is doing a great job, but only by asking and listening can we learn and improve.

 

Cheers

 

Stew

 

 

[Richard QuinnParticipant @richardquinn98511]

two things cleared up here…the 5 mm flats on crank bearings..I was stumped as to what the 5mm dimension was as 2mm hole on my drawings did'nts show square around lube hole…I did note the change from 10 to 12 crank but I did wonder if I was missing something.

Stewart, or anyone else, are up to date drawings available?…not sure where I found the ones I have but would love up to date if available. Have just made base and part of crank and bearing mounts..long way to go yet tho.

[CirclipParticipant @circlip]

Long gone are the days when Draughtsmen drew pictures of things they were acquainted with so stood half a chance of the bits fitting together. Having said that, there was/is still postings on "Errors on drawings". The ability to "Design" something doesn't automatically follow the ability to "Draw" it on a drawing package and Vicky Verky. After twenty five years using a board, ink and graphite I went on a course teaching me how to use Acad 12. After the series of basics and tricks to get lines on a screen and manipulation thereof to resemble recognisable objects, at the end of the course, passing written and practical tests resulted in a C&G certificate announcing competency in drawing using Acad 12. I often wondered how the Bricklayer and Car Salesman on the course would convince an employer of their ability to fit into a drawing environment, even though the bit of paper said they could?

Notwithstanding and no criticism to present company, the worst person to check a drawing is the originator and despite a "Checker" having signed off my drawings, I could find errors they had missed and this was a "Propper" Ingineer checking them.

Don't shoot the messenger if the request is to send three and fourpence.

Regards Ian.

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