By continuing to use this site, you agree to our use of cookies. Find out more

Member postings for jason udall

Here is a list of all the postings jason udall has made in our forums. Click on a thread name to jump to the thread.

<< First < Prev 11 12 13 14 15 16 17 18 19 20 21 Next > Last >>
Thread: Motor Input and Output Power
13/10/2015 18:45:11
Ketan.
You have my sympathy.

This specmanship is everywhere.

You can "fight" this by having the higher input ratings (and making these available) to hand.
So when asked you can inform the prospect.

"Yes sir we do appear to say our motor is lower power but that is because we tell you the power available to work not the heating effect on you workshop"..
Why don't we quote it like the others?..we have over the years found honesty and forthright advertising to be better recieved.
Now how many would you like?
Thread: Demagnetiser
11/10/2015 17:41:58
Pardon me if I am missing something.

You are taking a mains tranaformer..
Dissembling it ..retain primary. ..( possibly remove secondary)..reassemble laminations..in E form..

Now tell me how this.. apart from damage during dissembling. . is going to behave less safely than before?

Edited By jason udall on 11/10/2015 17:43:01

Thread: Injectors
09/10/2015 09:25:22
Maybe analogy would be better if "bouncers"..aka doorstaff was used rather than props...
Maybe.

Thread: Conjunction 9 10 15
09/10/2015 09:22:28
There isn't anyway to fix it.
But one of my bugbears is..
Title shows something ( say chuff chuff obstruse element)....but buried in the discussion about just which day they changed the shade of green used on the doors...there is an "off topic" post that is ..to me..actually interesting. .
As you can tell I am not a devotee of chuff chuffs esp. "Rivet counting"..but sometimes the topic wanders to include intresting matter. .
Just how do I mine for this gold?
Thread: Injectors
08/10/2015 20:35:11
Of course. .critical temperature. .
Forgot that. ..
So above 374 water won't be a liquid..
...
Mmm
08/10/2015 18:39:03
You've done it now
This has got me thinking.

What is the maximum pressure that steam can be generated at?

Let's see.
18 grammes of water evaporates to 22.4 l of vapour at stp.
..thus 22400 cc from 18 cc..
So 22400/18 = =1,244.4444444444 bar
Ie if boiler pressure exceeds 1244 bar.. what happens?
I suppose the water canstill evaporate but in theory the vapour/gaseous water has higher density than the water in the boiler....
Ok 1244 bar is probably out side of any model engineer ( I hope) aspirations. .but what happens?
08/10/2015 17:35:10
Again thanks for the explanations

In simple terms my problem was thinking hydro static not dymamic.

If you try to push open a door with 400 kg of rugby props holding it shut...you will make little progress. . But if you despite weighting 70 kg happen to be moving at say 600 m/S ..THAT door will open...
08/10/2015 08:53:47
Thanks all.

So it would be possible to construct a loop pf pipe with a pair of "nozzle"/ " jet"/ " venturi" that allows steam to leave boiler travel through loop and return to boiler..all via this assembly..this is like connecting both ends of a diode to the positive of a battery and noting a flow of current through the loop......mmm
07/10/2015 14:50:05
And if this seems odd take a look at vortex nozzles. ..very cold air from compressed air..
07/10/2015 14:47:44
All seems odd to me.
"Slow down the steam to overcome the boiler pressure"...???

That would seem to , when taken to extreme.allow a simple pipe loop . steam to steam. to induce a circulation ...
Mmm stick a turbine in the way and you have free energy...can't be right...
Yes I know these things work but always smelt abit fishy on the thermodynamic front.
Thread: Climb Milling
07/10/2015 14:21:28
As a miller of little or no experience I look forward to such a reasoned treatment.

Thread: 3D printer scam
07/10/2015 09:56:40
Thanks for highlighting this Maybe since this isn't just 3dprinter specific. Its a scam that could be applied to anything..a wider posting might be good.

For those who don't follow the link above..
The gist is.
Object advertised at great reduction of normal price.
Item to be dispatched via Aliexpress. ( oh that's good nice safe refunds policy)...
Vendor once order placed contacts you and says something along the lines of now being dispatched on slower/different carrier thus refund due. ..get refund by complaint to aliexpress...
Now here's the catch..you apply and getsaid PARTIAL refund ( for the carriage)..but this ends all futher refund claims against the whole price ..
...thus you pay say 40 quid..recieve 8 quid back...and the remainder stays with scammer along with the nonexistent product never shipped on the nonexistent carrier.

Edited By jason udall on 07/10/2015 09:58:09

Thread: What did you do today (2015)
02/10/2015 18:40:26
From my reading ( Washington post)
The EPA gave two grounds to penalise VAG
First the presence of a defeat "device". ( software/firmware?)
And secondly that such device is not declared in the build.

That qualifies as two infringments per vehicle...
Which at the quoted 37, 500$ per infringement adds up to 75, 000 $ per car...

Any way this is nothing new.
A ( as it happens vag) car manufacturer was "bragging " the ability to detect under test conditions ( around the 1990's).

Later two Japanese car manufacturers were arguing over how hybrid the others product was..specifically that inspection of the logs in the cars computer show that one model seemingly never used electric but was "mode locked" into petrol for all miles...never saw what happened ..but talk of withdrawal of congestion charge exemption was discussed.
28/09/2015 14:59:51
What I mean is..as often happens subjects not covered by the thread title come up. .and when they do they might be "hidden" by the apparent subject. Search engines do not always help..for example I have no objection to pictures of people "at it " , being on the web..I just don't wish those results when searching for "screw gauges uk"
...google..definitely delivers some "not safe for work" results....

Edited By jason udall on 28/09/2015 15:03:24

Edited By jason udall on 28/09/2015 15:04:09

28/09/2015 14:56:46
How about a" rule"..
When a posting to a ( in particular this) thread illicits more than ( say 3) responses.
Those postings are copied to another thread
, created for that purpose. .with the expectation that the thread continues there...
...
All win.
24/09/2015 23:22:27
Thanks Michael.

That article incuded a ref to another incedence from the 1998.

I had a case of deja vu..I knew I had read about this "identify if under test" wheeze before. .

Thread: Thread Rolling
24/09/2015 13:28:46
..looks like evolved/advanced type of knurling...

Yeah at say 1mm depth...but yes similar process. Generally with "milder" -less sharp- profile..
Thread: regenerative braking
22/09/2015 18:37:04
I have read ( maybe not understood but) all the above.

Heres my question.
Agiven motor is charaterised thus.
Stall current
Off load rpm.
Off load current
Max rpm ( mechanical.."centigugal"or bearing limits)


So far so good.
So to drive motor at off load rpm ( which we assume is lower than max rpm)
We feed a voltage sufficient to reach this rpm..dc for now.
So why is motor sinking so much less than the stall current?.
Well at stall we have say 24V and a few tenths of ohms thus we have hundreds of amps..
But at off load rpm we see 5A..?
Doing the arithmetic we see that the motor acts as if run on 1-2 V...what gives..well that back emf the motor is generating...say 22V...
PUSHING the other way leaving only 1-2V excess ..
Now take the point where the motor is loaded and throttled to half rpm...
Motor back emf falls and load current rises.....
Now apply brakes...
Well back emf is about ( pardon my guess ) 1/4 at this rpm so say 6V...
Mmm how do we charge a 24V battery from that. . (Yes I know ...inverter of some kind but lets keep this to the..fet/diode/switch level)?..



.
Thread: Thread Rolling
21/09/2015 17:20:58
Don't fear...manual thread rolls even exist for off machine work..
In fact thread rolling "taps" exist..
All this means that a 1/3rd hp bench operative can do it.. so just a matter of torque.
21/09/2015 17:16:37
My experience is with cnc usage

That said I would feed in at "screw cutting" feed ie just as if screw cutting.
..too fast with thin the threads..too slow will attempt to stretch the base metal...
Our Fette rolls disengaged when the spindle reversed and disengaged the coupling...
As to HP..well I have seen bar sheared off in half inch threads.. ( careful with the start diameter of you thread..)..
We threaded at 1500 rpm for m6 with a 15 hp spindle..
Didn't rpm didn't drop but then again tight servo control..so.....
<< First < Prev 11 12 13 14 15 16 17 18 19 20 21 Next > Last >>
Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Sign up to our Newsletter

Sign up to our newsletter and get a free digital issue.

You can unsubscribe at anytime. View our privacy policy at www.mortons.co.uk/privacy

Latest Forum Posts
Support Our Partners
cowells
Sarik
MERIDIENNE EXHIBITIONS LTD
Shopping Partners
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest

 

Donate

donate