Weld Stregth 3

[ID2008]

I have to design a 32 tooth triplex 1.25 inch pitch with a plate insert instead of making it out of 1 piece because of cost purposes. To do so the insert will have to be fillet welded both sides of the plate, however, I have very little idea how thick the weld line should be and how much stress can it takes. The insert plate is 16 mm thick. Is there any formula that will help me calculate the radial weld and weld thickness?

Thanks

 

[cloa]

Here's a useful reference although I can't speak from experience

http://www.engineersedge.com/weld/active_weld_height.htm

 

[metengr]

ID2008;
You can search the Internet and perhaps find bits and pieces of information that may help you to determine the tensile and shear load/length allowable stress. The easier method is to purchase the book below for a nominal cost;

Design of Welded Structures (Hardcover) by Omer W. Blodgett

The above book will be a valuable reference book for any weld shop.

 

[unclesyd]

I hardly second the suggestion by metengr of getting Blodgett's book, the best $15.00 you will ever spend.

Have you calculated and determined that the 1 1/2" center plate will carry the load?

If the center plate will carry the load as you drawing depicts your best bet would be to use enough welds to develop a full strength weldment, unless the sheave is way over designed.

Can you comeback with your max rpm and horsepower and how the sheave and driver are arranged?

Can you post some sizes like plate and hub dia?

 

[CoryPad]

I believe [blue]unclesyd[/blue] means he heartily seconds [blue]metengr[/blue].

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

Thanks for the correction. Just exactly want I intended. This has been one of those days.

 

[ID2008]

32 tooth triplex has a maximum 25 RPM. The sprocket will be driven by a triplex chain that hooks up to a 9 tooth sprocket which connects to a hydraulic motor that produces 2700 Nm torque. I have attached more dimensions to the drawing.

As for “Design of Welded Structures (Hardcover) by Omer W. Blodgett”, is there anyway I can see the contents (on-line) of it before purchasing it? I would like to know how much related the book is to my field prior to buying it. Otherwise I will make a trip to library.

Thank you

 

[unclesyd]

You need to get "Design of Weldments" by Omer W. Blodgett not the Structures Book.

This book for $15 is about 850 pages with diagrams, tables, formula etc concerning every aspect of fabrication by welding. It goes from the very simple to the more detailed design aspects.
The only real drawback is the lack of an index.

 

[metengr]

ID2008;

I have to design a 32 tooth triplex 1.25 inch pitch with a plate insert instead of making it out of 1 piece because of cost purposes.

After giving this some thought and looking at your proposed two piece fabricated rim and web sprocket, along with the stated dimensions, I believe this should be machined out of plate versus a two piece fabrication. The 16mm web would, at a minimum, require a full penetration weld to the sprocket rim based on the stated 2700 Nm torque. This fabricated gear would require a large amount of machining, fit-up, welding, that would probably require preheat and PWHT.

Most important, what is your material of construction, strength requirements (heat treatment condition) for the rim and web? This has to be factored into your cost benefit analysis for fabrication, which you indicated was done to arrive at a two piece fabricated assembly.

I would give serious consideration to manufacturing this sprocket from a 100mm thick plate, size the diameter of the sprocket rim and flame cut so that you can machine entire sprocket - rim and web. This would eliminate pre-machining, fit-up, and welding (preheat and PWHT)costs.

 

[ID2008]

Steel that will be used is 350 grades. It will be both preheat and PWHT. I am looking into at full weld penetration as well. However, my major concern is the calculating of force and whether the 16mm thick plate will be able to handle to load and stress or the weld gives way.

I have looked up on-line for "Design of Weldments" by Omer W. Blodgett, they are not $15, but more like $100 for a used one. Am I looking at a wrong edition?

Thank you

 

[metengr]

ID2008;
It sounds to me like you may be in over your head with this entire project. You really need to consult with a mechanical engineer that can help you with stress calculations for this sprocket. Once this is completed, you can evaluate suitable materials for the rim and web, optimize thickness based on material strength and decide if fabrication or one piece is the correct way to proceed.

 

[EdDanzer]

Your 16 mm plate is too thin to transmit the torque through the welds effectively. We have built several stack sprockets from plate sprockets because of delivery time constraints. Our rule of thumb is to have a hub plate the thickness of 50% of total sprocket widths. We try to have fillet welds equal to the plate thickness at the hub. In your case weld the center plate to the hub then finish machine before attaching the sprocket stack. The larger the diameter the smaller the weld has to be to transmit the torque required to break the chain.

Ed Danzer

http://www.danzcoinc.com

http://www.dehyds.com

 

[unclesyd]

Sorry about giving the proper directions.
If you go to the Lincoln website you could build a library for $100. You will see Design of Weldments for $15 on this page. Look around they are other good books.
I hate that you will have to pay $15 as I bought mine for $3, of course this was a long time ago.

https://ssl.lincolnelectric.com/lincoln/apdirect/store.asp?PID=16&cat=8

 

[strider6]

This paper from Lincoln can help u


Consider Direction of Loading When Sizing Fillet Welds

http://www.jflf.org/pdfs/papers/design_file2.pdf

S

Corrosion Prevention & Corrosion Control

 

[ID2008]

The design weldments cost $15 Plus $95 to ship it to Australia. Is there any other way?

 

[unclesyd]

Do they sell Lincoln Welding Equipment in Australia?
If so a distributor may be able to get you a copy. Another approach is see if your local library can get a copy of the book for you. We had a library on site and I got them to get several books for me. Another approach might be your Welding Society. The library and the Society get good rates on postage and shipping.

I can't understand the $95 shipping as I buy some vetinaery supplies from Australia and the UPS shipping is only about $3 - $5 for a couple of pounds.

What is the width of the flange?