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Author Topic: Things you have learned this weekend.  (Read 5764 times)

Brian60

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Things you have learned this weekend.
« on: June 08, 2015, 12:02:04 pm »

I have learned that unlike car paints, that are rubbed back with 1000grit wet or dry paper and then clearcoated and rubbed down again for a superior finish. Humbrol enamels can't be rubbed / cut back!

I rubbed back the car paints lovely, them clearcoated with 2 coats of Humbrol SatinCote. On rubbing it back with 1500 grit it just made a complete mess of the surface, lots of lines and scuffs. I gave it a wipe over with Humbrol thinner on a cloth which softened the surface, then redid a third clearcoat. Unfortunately many of the sanding marks are still showing through {:-{

So I have learned once you have used Humbrol enamels, accept the surface for what it is, don't even think about cutting it back for a finer finish!

Martin [Admin]

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Re: Things you have learned this weekend.
« Reply #1 on: June 08, 2015, 12:52:28 pm »


There is a 4MPH  difference between my SatNav and the car speedo.... which one do I believe?!

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NFMike

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Re: Things you have learned this weekend.
« Reply #2 on: June 08, 2015, 12:55:49 pm »


There is a 4MPH  difference between my SatNav and the car speedo.... which one do I believe?!


Satnav.
Car speedos are always calibrated on the 'safe' side as legally they have to read between +10% (approx) and -0%.

NFMike

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Re: Things you have learned this weekend.
« Reply #3 on: June 08, 2015, 12:58:13 pm »

So I have learned once you have used Humbrol enamels, accept the surface for what it is, don't even think about cutting it back for a finer finish!
Now that is interesting. Presumably it may apply to other paints as well.
Maybe Stavros can shed light on that.

Brian60

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Re: Things you have learned this weekend.
« Reply #4 on: June 08, 2015, 02:37:13 pm »


There is a 4MPH  difference between my SatNav and the car speedo.... which one do I believe?!



Our Picasso is the same, satnav always says you are going slower than the speedo.  I have noticed on Brit motorways (lots of 50mph zones at moment) the amount of drivers who are easily in excess of 60mph, Do they have some sort of psychic ability to cancel out the average cameras?

Bob K

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Re: Things you have learned this weekend.
« Reply #5 on: June 08, 2015, 03:04:27 pm »


There is a 4MPH  difference between my SatNav and the car speedo.... which one do I believe?!


Legally, the car speedo. These are built with a mandatory 10% under-reading so you can't blame the speedo if you are nabbed speeding.  ie:  When showing 30 you are doing approx 27, and when showing 70 you are going ~63.  The SatNav is showing a more representative actual speed, but is not updated as continuously like your speedo. 

See http://www.thecarexpert.co.uk/how-accurate-is-a-car-speedometer/
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U-33

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Re: Things you have learned this weekend.
« Reply #6 on: June 08, 2015, 03:39:48 pm »

What did I learn this weekend?


The lady is ALWAYS right... :-X
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Colin Bishop

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Re: Things you have learned this weekend.
« Reply #7 on: June 08, 2015, 03:48:41 pm »

Car speedos also have to allow for tyre wear, for a given road speed a worn tyre will be a smaller diameter than when new and therefore rotating more rapidly.

Colin
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plastic

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Re: Things you have learned this weekend.
« Reply #8 on: June 08, 2015, 04:22:35 pm »

I learned that 49 is a good age to retire!  :-))
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roycv

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Re: Things you have learned this weekend.
« Reply #9 on: June 08, 2015, 04:59:33 pm »

Hi Brian I thought it was me!  Just been rubbing down with new Humbrol white paint and if it is a tad thick it does not dry and scuffs up when using wet and dry. The older Humbrols seem OK
Frustrating!
regards Roy
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Brian60

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Re: Things you have learned this weekend.
« Reply #10 on: June 08, 2015, 06:24:31 pm »

Car speedos also have to allow for tyre wear, for a given road speed a worn tyre will be a smaller diameter than when new and therefore rotating more rapidly.

Colin
Not unless your car is more than 20 years old.

Since the early 80's car speedos have taken a drive from the gearbox output shaft, so irrespective of wheel diameter it will always read the same. Even more up to date ones have done away with the drive and use a sensor on the gearbox via the vehicle ecu to calculate speed.

Brian60

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Re: Things you have learned this weekend.
« Reply #11 on: June 08, 2015, 06:33:48 pm »

Hi Brian I thought it was me!  Just been rubbing down with new Humbrol white paint and if it is a tad thick it does not dry and scuffs up when using wet and dry. The older Humbrols seem OK
Frustrating!
regards Roy

I saw this explained on a plastic modelling forum Roy. Its seems for some time Humbrol had paint manufactured in the far east. But the product was thin and watery with poor coverage ( I have a tin of yellow!) Humbrol received so many complaints about the quality of the paint that they have moved production back to the UK. New Humbrol paint is more like the thick stuff of years ago, trouble is there are still retailers with stocks of the older stuff. You can tell the difference by comparing  tinlets, Thin watery stuff on the right, thick gloopy good stuff on the left.

tony23

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Re: Things you have learned this weekend.
« Reply #12 on: June 08, 2015, 06:38:51 pm »

also all the car spray paints that Halfords sell cannot also be rubbed down with wet'n'dry or compounded they dry hard to the touch but soft to work on 'bring back good old cellulose'!
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roycv

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Re: Things you have learned this weekend.
« Reply #13 on: June 08, 2015, 07:36:47 pm »

Thanks Brian.  I bought mine on ebay not for cost but for the size of tin.  But the tin printing ties up.
Thanks again Brian I shall ditch mine.
regards Roy
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ballastanksian

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Re: Things you have learned this weekend.
« Reply #14 on: June 08, 2015, 08:40:01 pm »

I bought a tin of Humbrol 49 matt varnish recently and it was as thick as treacle, if not thicker with a caramel colour in the tin. It needs thinning down to use, even with a brush, as otherwise any effects you might use such as tinting the varnish will not work at all well.

I have found recent purchases of all consistencies but will be sticking with their enamel for certain jobs.
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malcolmfrary

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Re: Things you have learned this weekend.
« Reply #15 on: June 08, 2015, 08:51:09 pm »

Quote
Since the early 80's car speedos have taken a drive from the gearbox output shaft, so irrespective of wheel diameter it will always read the same. Even more up to date ones have done away with the drive and use a sensor on the gearbox via the vehicle ecu to calculate speed.
I really don't see how taking a drive for a speedo from one place or another can have any compensating effect on the differing tyre diameter.  It shows how fast the transmission is rotating, but is unable to directly know how fast the world is passing by.  A wheel with a smaller diameter must rotate faster for any given speed, so a speedo, being an instrument for showing the rate of transmission revolutions, must show a faster speed for any given actual speed.  Probably why a fifth wheel is often used for accurate measurement when cars are being tested.
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Klunk

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Re: Things you have learned this weekend.
« Reply #16 on: June 08, 2015, 08:54:36 pm »

Don't tell you wife you bought a banana.  She wanted it. Its very hard to tell her that you actually bought another boat!
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Colin Bishop

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Re: Things you have learned this weekend.
« Reply #17 on: June 08, 2015, 09:10:48 pm »

Quote
really don't see how taking a drive for a speedo from one place or another can have any compensating effect on the differing tyre diameter.  It shows how fast the transmission is rotating, but is unable to directly know how fast the world is passing by.  A wheel with a smaller diameter must rotate faster for any given speed, so a speedo, being an instrument for showing the rate of transmission revolutions, must show a faster speed for any given actual speed.  Probably why a fifth wheel is often used for accurate measurement when cars are being tested.

Exactly!
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Stavros

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Re: Things you have learned this weekend.
« Reply #18 on: June 08, 2015, 10:01:09 pm »

Brian 56 OH DEAR ME................Never have I come accross and enamel that you can cut back and polish it just dont happen
 
Tony23.........sorry to say buy you are incorrect in what you are saying........Halfords paint CAN BE rubbed down and polished back with ease.....1000 grit used wet/dry and soap then 1500 done the same followed up with 2500 grit wet and use soap and simply polish up with Farecla rubbing compound.
 
Enamels by their nature are an oil based  paint that relies on puse air drying usually without the aiod of a solvent...yes of course you can thin them doiwn usually 10% dilutant.
 
Aerosol that are supplied by Halfords are similar to the old cellusloe type paint and rely on the thinners to dry them fast and are also classed as air drying .
 
Proper car paint ie 2 pack is a different kettle of fish as they are a chemicla drying paint so dry rock hard
 
Dave
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Big Ada

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Re: Things you have learned this weekend.
« Reply #19 on: June 09, 2015, 06:33:49 pm »


There is a 4MPH  difference between my SatNav and the car speedo.... which one do I believe?!


Its all to do with Altitude, so I was informed.
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Colin Bishop

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Re: Things you have learned this weekend.
« Reply #20 on: June 09, 2015, 06:54:31 pm »

Quote
Its all to do with Altitude, so I was informed.

Not all to do but checking online I have found the following:

 "On steep hills and winding roads the sat nav will be less accurate as you are covering less linear distance over the earth's surface. "

Sounds logical!

Colin
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Re: Things you have learned this weekend.
« Reply #21 on: June 09, 2015, 07:17:52 pm »

On straight and level roads your satnav indicated speed is far more accurate than your car's speedo.
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NFMike

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Re: Things you have learned this weekend.
« Reply #22 on: June 09, 2015, 09:02:43 pm »

"On steep hills and winding roads the sat nav will be less accurate as you are covering less linear distance over the earth's surface. "
On straight and level roads your satnav indicated speed is far more accurate than your car's speedo.

I expect that on any surfaced, public road GPS will be more accurate than the car speedo, even on hills/bends.
A 'steep' hill in your car is about 10% - actually a gentle slope; and if you look at an OS map those 'bends' aren't really all that tight, and the few that are a tight right-angle you'll be going slow and trying to follow the road - not worrying about your exact speed :)

rem2007

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Re: Things you have learned this weekend.
« Reply #23 on: June 10, 2015, 07:33:00 am »

Once again I have learned to duck when walking out of my shed >>:-(, eventually that door will be made taller, just a little less hair on the every increasingly larger bald spot. {-)

Robert

Still it was excellent weather, to sit and have a lager and nurse the afore mentioned injury
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Brian60

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Re: Things you have learned this weekend.
« Reply #24 on: June 10, 2015, 06:14:45 pm »

Once again I have learned to duck when walking out of my shed >>:-( , eventually that door will be made taller,

Why not just lower the step? :embarrassed: %%
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