Thursday, March 3, 2011

CrazyEngineers Forum

CrazyEngineers Forum

Strain Gage for Measuring Load on Shaft

Posted: 03 Mar 2011 01:24 PM PST

Hello everybody,

I'm new here, have visited on several occasions and lurked in an effort to learn - but this is my first time posting.

I'm an engineering student working on a project and am working with strain gages for the first time. The project consists of a rotating aluminum shaft (3 mm in diameter, 10 mm in length), with a motor on one end and a variable load at the other (load varies between 0 to 8kg). I'd like to mount a strain gage onto this shaft to be able to measure the load.

The shaft does not rotate continuously, only back and forth within a range of approximately 120 degrees. My thought is to model this problem as a bending load at the end of a shaft and determine the deflection in the aluminum shaft. Doing this, I might be able to spec out a strain gage. My problem is I'm not sure how to use these deflection / stress calculations to determine an appropriate strain gage - I've been looking through the Omega and Vishay catologues. I'm also not sure if it's even reasonable to expect to find a strain gage that is small enough to fit on a 3mm shaft, that has a resolution capable of measuring such small deflections.

Would anyone familiar with Strain Gages be able to provide a little insight / help for a lost student? :) Thanks!

Thrust Runner Design

Posted: 03 Mar 2011 01:19 PM PST

The results of sectional-3D FEA on a Thrust Runner of the Thrust Bearing in a Pump shows that the Runner "bows" under the thrust load. The axial displacement of the periphery of the Runner is ~60 µm. The thickness of fluid-film between the Thrust Runner and Tilting Pads is estimated to be ~10 µm.

Radial interference of 5 mils/inch diameter is modeled between the Shaft and the Runner. The applied loads are: (i) Interference, (ii) Centrifugal, and (iii) Axial Thrust (mapped from 1 Tilting Pad on to the Runner Surface).

I am concerned that the excessive deformation on the periphery of the Runner will cause the lubricant film to be unsustainable, and drastically reduce the load-carrying capacity.

My question is, how much displacement is allowable on the Runner?

Heat Exchanger Fabrication Question?

Posted: 03 Mar 2011 09:43 AM PST

I posted this in Chemical Engineering section but might be more appropriate here.

In a dilemma about exactly how tubes are stuffed in a multi baffle plate heat exchanger. The half plate baffles are already stitch welded on inside of exchanger pipe.

With only a 1/64" clearance in holes for tubes I cannot fathom how one would insert a 35 ft tube thru the full length of a pipe with half baffle plates every 8 ft..

It seems like you would need a broom handle type wood stick aligned thru full length of pipe thru each baffle and then use it as a guide for the tube.

I don't know, have you had any experience around heat exchanger fabrication?

Appreciate your comments and advice,
Kelly

Heat Exchanger Fabrication Question?

Posted: 03 Mar 2011 09:34 AM PST

In a dilemma about exactly how tubes are stuffed in a multi baffle plate heat exchanger. The half plate baffles are already stitch welded on inside of exchanger pipe.

With only a 1/64" clearance in holes for tubes I cannot fathom how one would insert a 35 ft tube thru the full length of a pipe with half baffle plates every 8 ft..

It seems like you would need a broom handle type wood stick aligned thru full length of pipe thru each baffle and then use it as a guide for the tube.

I don't know, have you had any experience around heat exchanger fabrication?

Appreciate your comments and advice,
Kelly

Hiya Anita Here

Posted: 03 Mar 2011 09:19 AM PST

Hello,

Nice to see the fellow engineers hanging out here. Looking forward to interact with quite a few amongst you!!!!!

CHP feasibility study

Posted: 03 Mar 2011 08:24 AM PST

Hey guys, was wondering if you could give me some advice on the following :
I want to install a chp machine to power a known intraday load profile. How do I pick which is the best sized generator to power my electric load since I will have the economic benefit of exporting to the grid. So how do I balance installed capacity with pricing ?
Apart from my electric : thermal ratio how do I bring the thermal bit into the equation?


Thanks

how to discard sent mail ?

Posted: 03 Mar 2011 07:28 AM PST

Is there any alternate to discard sent mail in gmail ? :(

Width of Memory

Posted: 03 Mar 2011 06:13 AM PST

Hi,
Why does most of the memories have byte width , i.e , each location of a memory has a width of 8 bits. Why can't it be 4 bits or 16 bit or any other no.?

Aircel 3G SIM Cards For Tablets

Posted: 03 Mar 2011 05:49 AM PST

Aircel thinks that 10% of their existing customers will switch to 3G networks and are planning to launch SIM cards for the Tablets. Aircel has over 2 million customers in Kerala and think that Kerala would be one of the top destinations that will convert to 3G. Quite apparantly, there are many Keralites who have their family members abroad and would love to talk to them over video via 3G ;) .

That's a good news for non Apple tablet owners. iPad seriously needs a SIM card slot! :|

Airtel 3G Tariff Review Launched In Bangalore, Delhi, Coimbtore,Chennai, Jaipur,Delhi

Posted: 03 Mar 2011 05:45 AM PST

Airtel has launched 3G services in Bangalore, Delhi, Coimbtore, Chennai, Jaipur, Delhi. I did not see unlimited data plans in the list (checked few cities) so wondering how do you all think about Airtel 3G plans.

Are they competitive enough? Or BSNL still rules?

LI2 Innovations Workshop on Android Application Development

Posted: 03 Mar 2011 05:35 AM PST

I recently attended a workshop by LI2 Innovations on Android Application Development.
The workshop's duration was of 2 days and they charged us Rs 800/- :confused:

On the first day, they explained concepts about Core JAVA, but it was very difficult to handle 100 students, out of which 50 percent did not know what System.out.println is or how to install JDK.

On the second day, when they introduced the students to Google Lab's Beta Product: App Inventor, the crowd was calm and we developed 4 applications.
But much to my dismay, all those apps are available on the internet freely as tutorials.
Check here: Tutorials - App Inventor for Android

I just thought I would share my experience with you all.

Airtel E1731 USB Stick 7.2 mbps Modem - Speed Review

Posted: 03 Mar 2011 05:31 AM PST

Airtel's launched 3G across few cities in North India and has introduced USB 3G Modem Sticks: E1731.

The E1713 has following features -

Speed HSDPA 7.2Mbps, HSUPA 5.76Mbps
Network: customized simlock to airtel network, PnP
Chipset: qualcomm MSM6290
Radio for 3G : HSDPA/UMTS 2100 MHz, receive diversity

The tech-specs are impressive but do we have first-hand information on the speed and performance of E1731? Please share your feedback for the benefit of larger audience here on CrazyEngineers :)

Doubt regarding DSB SC,SSB SC modulation techniques

Posted: 03 Mar 2011 05:22 AM PST

Hello engineers,
I have a very big doubt in DSB SC,SSB SC modulation techniques.we know that the message signal is modulated with a carrier signal of a high frequency for various advantages.my doubt is that in these techniques ,we are suppressing the carrier.what is the need of modulating a signal with a carrier signal and then again suppress it?

Is iPad A Fad Or Necessity?

Posted: 03 Mar 2011 05:22 AM PST

We never knew we'd need a tiny slate with a magical touch screen on it that'd begin to replace our laptops. However, we all must agree that gadgets are evolving rapidly with faster processors and better graphics.

iPad 2 sets the benchmark for other similar devices and takes us a step ahead into the future. There are many CEans who'd be willing to buy tablets. I wish to know whether engineers think iPad (and tablets) is a necessity or a fad?

Confused in which field should i do my summer training

Posted: 03 Mar 2011 05:11 AM PST

Hello i m 2nd yr Ec student i m very confused in which field should i do my summer training and also how get in iitk for summer training........
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