Norden mill engine

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Norden mill engine

This topic has 7 replies, 2 voices, and was last updated 11 May 2013 at 14:50 by Sub Mandrel.

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11 May 2013 at 11:23 #119509
Eric Cox
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@ericcox50497
Clarification on the Norden mill engine crank shaft ME4456 P 692

What is the overall length of the crank shaft and is the left hand keyway only 3/8" long

Why are the key ways dimensioned from the opposite end to which you would start cutting

Edited By Eric Cox on 11/05/2013 11:34:55
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11 May 2013 at 11:23 #119516
Eric Cox
Participant
@ericcox50497
Clarification on the Norden mill engine crank shaft ME4456 P 692

What is the overall length of the crank shaft and is the left hand keyway only 3/8" long

Why are the key ways dimensioned from the opposite end to which you would start cutting

Edited By Eric Cox on 11/05/2013 11:34:55
11 May 2013 at 11:23 #38765
Eric Cox
Participant
@ericcox50497
11 May 2013 at 12:07 #119517
Sub Mandrel
Participant
@submandrel
HI Eric,

Mea culpa, the 2 7/8" dimension was a mis-typing of 1 7/8". Also the thickness of the crank disc is missing, it should be 1/8". The drawing in ME is with a % or so of full size.

I've amended the master copy of the drawings.

Keyways are dimensioned from the disc end as this is the point as it is the location of the crank pin over the centre of the piston that is the critical position. Errors at the far end will not siginificantly affect the model.

Note that the keyway sizes are indicative, as they will depend on various tolerances according to assembly of the bearings/thickness of parts as made etc. Also they need to extend beyond the fixed parts to allow for assembly, though the amount is not critical.

Hope that helps,

Neil
11 May 2013 at 12:07 #119526
Sub Mandrel
Participant
@submandrel
HI Eric,

Mea culpa, the 2 7/8" dimension was a mis-typing of 1 7/8". Also the thickness of the crank disc is missing, it should be 1/8". The drawing in ME is with a % or so of full size.

I've amended the master copy of the drawings.

Keyways are dimensioned from the disc end as this is the point as it is the location of the crank pin over the centre of the piston that is the critical position. Errors at the far end will not siginificantly affect the model.

Note that the keyway sizes are indicative, as they will depend on various tolerances according to assembly of the bearings/thickness of parts as made etc. Also they need to extend beyond the fixed parts to allow for assembly, though the amount is not critical.

Hope that helps,

Neil
11 May 2013 at 14:29 #119537
Eric Cox
Participant
@ericcox50497
Many thanks Neil.

"as they will depend on various tolerances" What's this, a reference to tolerances?. Don't you know tolerances have no place in model engineering
11 May 2013 at 14:29 #119543
Eric Cox
Participant
@ericcox50497
Many thanks Neil.

"as they will depend on various tolerances" What's this, a reference to tolerances?. Don't you know tolerances have no place in model engineering
11 May 2013 at 14:50 #119541
Sub Mandrel
Participant
@submandrel
Just being pragmatic! I try to use rule dimensions where appropriate and not critical – no point in making people chase spurious accuracy or abandon a 1/8" thick part because it is 0.024", but it means that commons sense is needed on assembly. This is especially true of the bevel gears where the position will almost certainly need to be tweaked to get smooth running.

Neil
11 May 2013 at 14:50 #119547
Sub Mandrel
Participant
@submandrel
Just being pragmatic! I try to use rule dimensions where appropriate and not critical – no point in making people chase spurious accuracy or abandon a 1/8" thick part because it is 0.024", but it means that commons sense is needed on assembly. This is especially true of the bevel gears where the position will almost certainly need to be tweaked to get smooth running.

Neil
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