Previous in Forum: High Temperature In Thrust Bearing Of Steam Turbine   Next in Forum: Standards for Plastigague
Close
Close
Close
16 comments
Power-User

Join Date: Oct 2010
Location: Base in Madrid, Spain. Updated location every several months.
Posts: 126
Good Answers: 3

Design of Gears in Old Machines

07/31/2011 7:16 PM

Dear all,

seeing an old machine to manufacture fabrics, awoke my curiosity about the reasons for multiple designs of the radial arms for the different pinions and gear wheels, specially the "ondulated/swan neck" ones (they look like "flexibles", maybe a desirable property at some point).

The torque to be driven, the manufacturing process, economisation in material, seems the logical ones.

Do you know some other reasons behind it?.

Salu2,

__________________
Everyday learning.
Register to Reply
Pathfinder Tags: Ancient machinery gears old gears
User-tagged by 1 user
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United States - Member - New Member Engineering Fields - Control Engineering - New Member

Join Date: Mar 2006
Location: Washington USA
Posts: 566
Good Answers: 53
#1

Re: Design of gears in old machines.

07/31/2011 7:21 PM

The castings were created by artisans.

Register to Reply Score 1 for Good Answer
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 21005
Good Answers: 781
#2

Re: Design of Gears in Old Machines

07/31/2011 9:52 PM

The really frilly ones included bas-relief dragons, serpents, and such like.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
2
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3053
Good Answers: 140
#3

Re: Design of Gears in Old Machines

08/01/2011 1:38 AM

I have seen this in old weaving machines everywhere. It has been the engineering approach for pulsating processes, where saw-tooth positioning and mechanical pressure snapshots were combined with cast frames and not too sophisticated bearings (if any). The long spikes provide some more elasticity to keep the gears running longer and softer. The machine vibrates a little less also. These "S" spikes are also found in old sewing machines driven by feet movements. Gives a more comfortable "drive". Straight spikes are shorter and less flexible. The gears are commonly cast and breakage occurs less than with straight spikes, because a more uniform load pattern occurs in the proximity of the spike to outer ring.

__________________
Plenty of room here
Register to Reply Good Answer (Score 2)
Power-User

Join Date: Oct 2010
Location: Base in Madrid, Spain. Updated location every several months.
Posts: 126
Good Answers: 3
#5
In reply to #3

Re: Design of Gears in Old Machines

08/01/2011 11:51 AM

Dear dvmdsc,

many thanks for your clear and detailed answer.

Abel

__________________
Everyday learning.
Register to Reply
2
Guru
Engineering Fields - Electromechanical Engineering - Technical Services Manager Canada - Member - Army brat Popular Science - Cosmology - What is Time and what is Energy? Technical Fields - Architecture - Draftsperson Hobbies - RC Aircraft - New Member

Join Date: Sep 2006
Location: Clive, Alberta, Canada
Posts: 5907
Good Answers: 204
#8
In reply to #3

Re: Design of Gears in Old Machines

08/01/2011 11:42 PM

I think that Vibration reduction is probably the correct answer.. why they are more resistant to breakage with brittle cast iron. Before the days of Analytical Cad programs, the old designers had vivid imaginations, and more time to focus, and fewer things to focus on... so they had the ability to 'see' the problems, and 'see' the solutions. Some old tech could not be imagined today. Not everything new is advanced, but stands on the shoulders of what was brilliant.

chris

Register to Reply Good Answer (Score 2)
2
Associate

Join Date: Oct 2010
Location: Wiltshire, England.
Posts: 42
Good Answers: 4
#12
In reply to #8

Re: Design of Gears in Old Machines

08/02/2011 7:32 AM

'Analytical CAD programs' are tools, they will not produce good design. The 'old designers' had insight and depth of understanding, nothing whatsoever to do with 'more time to focus' or a 'vivid imagination'. There are still such people, they are not produced by a University degree (although some will have one). They can look at the workings of a machine and understand the reasoning and mind of the designer, back through many layers of thought. They can look at a requirement and solutions (with their problems) will present themselves.

You are certainly correct in saying these Designers had the ability to 'see' the problems, and 'see' the solutions. They are here today, but it is not a common gift.

These people will generally work best alone.

Henry

Register to Reply Good Answer (Score 2)
Guru
Hobbies - Musician - New Member Australia - Member - Torn and breading Engineering Fields - Nanoengineering - New Member APIX Pilot Plant Design Project - Member - New Member

Join Date: Jun 2006
Location: Magnetic Island, Queensland, Australia
Posts: 3721
Good Answers: 74
#14
In reply to #12

Re: Design of Gears in Old Machines

08/02/2011 5:44 PM

Hi Henry

When I saw the machine depicted I had to take a deep breath because of the beauty of it. Just like looking at a piece of art. The ACE #1 said that in one short sentence. What I also recognized at once was that the elegant curves are not there because some artisan was bored or had excess materials. Next was the casting challenge of such and those aspects were dealt with by other participants in this thread.

I am certain that Chris knows the limits of CAD design. I know this from personal experience with him and his abilities in using this tool. After sending him some 2D drawings (a while back) he was able to create CAD files. Not that these were created to prove anything but they were necessary to make complicated mechanics more obvious to any third party viewers. These people are sometimes not even able to read a 2D plan so having a CAD with moving parts was and still is a must if one needs to communicate ideas with bean counters.

One day, when things were getting to the final stages and intricacies were being recognized by Chris he rang me. It was 4am here and we had a power black out. This made it impossible for me to open preliminary files or even look at drawings. What I did was stay in bed, visualize the area he had identified difficulties and we solved the issues there and then, off the top of my head and over the phone. I could literally see the section of concern.

These people will generally work best alone.

Generally yes, but nowadays, through the existence of such technology, cooperation, co-inventing and inspired feedback have entered our lives. I would not be without it although my imagination and practical abilities would allow me to stay a lone wolf, I will not insist. In the end, when and if it ever gets to be manufactured it will save a lot of time and of that we don't have much.

BTW Henry welcome to CR4. I am looking forward to more eloquent comments by you which seem to be just around the next corner.

More of it, Ky.

__________________
The Twain Has Met
Register to Reply
Power-User
Popular Science - Weaponology - New Member

Join Date: Jun 2011
Location: Berkeley, CA USA
Posts: 128
Good Answers: 4
#13
In reply to #8

Re: Design of Gears in Old Machines

08/02/2011 4:19 PM

The biggest thing Analytical Cad programs gave us is machines that out last the warranty by a few months :~). Sure there are lots of other good tings but that is the most irritating result of Analytical Cad programs.

__________________
Working to end the use of carbon for energy
Register to Reply
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3053
Good Answers: 140
#16
In reply to #8

Re: Design of Gears in Old Machines

08/03/2011 1:15 AM

That is correct. You can buy hundreds of straight spiked wheels as hand wheels, and also as belt drive wheels for straight flat belts or V-snares. Production has little to do with it. In the mechanical revolution 18'hundreds, casts, even in sand were pretty good already.

Especially for big wheels, spikes produce a considerable gain in weight. Cast spikes wheels do not produce a lot of cracks at all in production, that is just why cast iron or steel is used.

Whole engine blocks are casted, with completely different stress loads and much more critical dimensions. Sorry but cast material when cooled down in the right proportions DOESN'T CRACK AT ALL. Who has cracks during solidifying, works dirty or has to optimize his casting and/or cooling process. Everyone can believe what he wants but a lot of comments to this post are not relevant for the machine shown.

In a weaving process, things can go terribly wrong. Thread can accumulate between teeth and if forming a thick enough obstacle a gear with straight spikes is a sitting duck for breakage.

__________________
Plenty of room here
Register to Reply
Power-User

Join Date: Apr 2011
Location: pittsburgh
Posts: 180
#4

Re: Design of Gears in Old Machines

08/01/2011 3:53 AM

machines were designed with the technology available. i'm always amazed by early engineering. was it actually designed in, or was it a [common sense] or [commom knowledlege] sort of thing? alot of them are still running. that says alot about what we're building today.

Register to Reply
Power-User
Engineering Fields - Mechanical Engineering - New Member Engineering Fields - Marine Engineering - New Member Engineering Fields - Aerospace Engineering - Aeromarine Vehicle Engineer

Join Date: Mar 2008
Location: Baltimore, MD
Posts: 148
Good Answers: 5
#6

Re: Design of Gears in Old Machines

08/01/2011 8:41 PM

I really like the picture. Thanks

I remember seeing handwheel for steam valve having a similar spoke design. And now looking at it, probably an ideal spoke design for use of a spanner wrench. Maybe that was one of its functions. Just an observation and thought

Register to Reply
2
Power-User

Join Date: Jun 2009
Location: Australia
Posts: 277
Good Answers: 45
#7

Re: Design of Gears in Old Machines

08/01/2011 10:44 PM

I don' know for sure, but art aside I think it is the case that old gears such as those shown were invariably made of cast iron - a wonderful material except for the fact that it is not real good in tension and has limited ductility.

I've always thought that curved spokes were used to minimise tensile forces (and failure) in the spokes during use and or during casting - has anyone done the maths.

Register to Reply Good Answer (Score 2)
6
Associate

Join Date: Jul 2008
Location: Glos, England
Posts: 47
Good Answers: 10
#10
In reply to #7

Re: Design of Gears in Old Machines

08/02/2011 2:40 AM

Hi all,

TrevorM has (as far as I know) the right answer - if you try to cast straight spokes in grey cast iron they (almost invariably) crack as a result of shrinkage during solidification. If you cast in a curve or swan neck they don't.

I once was (peripherally) involved in casting a replacement wheel (straight spoked) to match the others on a travelling van to be towed by a steam traction engine - the sort that the driver used to live in whilst out on the road - and it took several attempts (even with modern knowledge to help us) as the spokes kept cracking.

The solutions are certainly very attractive to the eye although they don't give the strongest possible design, so are not elegant / efficient in terms of material usage (if you could make any shape successfully.

For info grey cast iron has a coefficient of expansion of 11x10^-6 / degree C - about the same as steel, about 1/2 that of Al and about twice that of glass, but it's really the very limited ductility and relatively high freezing point that cracks it.

DP

__________________
If you can't explain a concept in simple terms, you don't understand it well enough.
Register to Reply Good Answer (Score 6)
Guru
Hobbies - Musician - New Member Australia - Member - Torn and breading Engineering Fields - Nanoengineering - New Member APIX Pilot Plant Design Project - Member - New Member

Join Date: Jun 2006
Location: Magnetic Island, Queensland, Australia
Posts: 3721
Good Answers: 74
#9

Re: Design of Gears in Old Machines

08/02/2011 2:13 AM

27

Re: What Machine/Device Impressed you Recently?

O.T, I know. Is this great or what?

__________________
The Twain Has Met
Register to Reply Off Topic (Score 5)
Participant

Join Date: Jun 2011
Posts: 1
#11

Re: Design of Gears in Old Machines

08/02/2011 6:49 AM

Dear Salu2:

In the case of a cast metal this is melt up to a certain temperature and it is poured in his liquid version in a sand mold. Once the metal start to cooling down a material contraction take place. If the sand mold is too hard molded, on the light sections of the cast piece quite often appears a crack. So a relation on the mold hardness, pouring temperature, a design figure of the part and commune sense will help to reduce chances to get scraped parts on a normal production lots.

By the way, not all the sheaves has the goose neck design on the OEM's parts.

Ricardo.

Register to Reply Off Topic (Score 5)
2
Guru

Join Date: May 2010
Location: in optimism
Posts: 4050
Good Answers: 129
#15

Re: Design of Gears in Old Machines

08/02/2011 10:10 PM

As mentioned by TrevorM initially and dieselphil expanded on; cast iron spokes tend to crack due to shrinkage tension created in casting.

Add to this cast iron 'ages', (meaning is changing dimension for some time after casting) you can see a rationale in the approach to the different solidity verses tooth pitch, over the range of gears.

In days of old, these gear blanks would be cast, tidied up and left outdoors to 'age' before machining. Some machinery manufactures still do this for such as precision mills and grinding machines, rather than artificial aging.

So, in this machine, where a fine pitch is used, mainly for precise ratio change, (rather than power), and low solidity is desired, the S form gives a more stable and stress resolved annulus, so the greater roundness required for a fine tooth pitch, more accurate diameter stability required for the tighter center distance tolerance, and less tendency to warp laterally, where a narrow tooth face is desired.

The only other way to achieve this is via a solid disc, as in the small gear, but the ability to cast large thin discs in sand is very thickness limited.

Were you to measure the coarser pitch gear behind, you would likely find each bridge over a cutout is 'other than round' - but not out enough to seriously impact the meshing or ratio. You would hear it though and probably see in the wear.

__________________
There is no sin except stupidity. (Oscar Wilde, Irish dramatist, novelist, & poet (1854 - 1900))
Register to Reply Good Answer (Score 2)
Register to Reply 16 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be Good Answers:

These comments received enough positive ratings to make them "good answers".

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

34point5 (1); abelmh (1); Ace Boeringa (1); avilarado (1); chrisg288 (1); dieselphil (1); dvmdsc (2); Gannet (1); HenrytheEngDes (1); jlstitt (1); ky (2); regsoft (1); Tornado (1); TrevorM (1)

Previous in Forum: High Temperature In Thrust Bearing Of Steam Turbine   Next in Forum: Standards for Plastigague

Advertisement