Large Scale Central

Scale Tollerance

Modeling
#1

I’m playing around with scaling out a tank car in 1:20.32. I don’t plan on measuring my cuts with a micrometer but I’d like things to be pretty close. I chose +/- 1.5 scale inches as my tolerance and that seems to work out pretty well. It allows me to keep my models dimensional measurements no smaller than eighths.

Of course this works only on larger items. Things like stake pockets, grab irons, etc. will need to be a lot closer, but most of those will probably be purchased as parts anyway.

So, when you scaling a model what is your tolerance ?

#2

“Close enough”. Unless I’m doing a specific prototype, I dont worry about it. Even the EBT steel cars that I did, they were 34 feet, but when you read about them, they were “around” 34 feet long, give or take an inch.

#3
Jon Radder said:
So, when you scaling a model what is your tolerance ?
Now I'm a newbie so don't beat me up too bad...but I would say my tolerance would be how bad do I want to see the finished model on the line or how anal am I gonna get in my shop(man shed) detailing the thing to run outside? Are the manufactures of this stuff worried about critical detail. Some do but you pay dearly. As the kids say on the car repair forums "I dunno" Do you really think guys like me are gonna notice that your off in your dimensions when you post a picture of the finished model? ...Hell no.....are you turning into a rivet counter Jon? Just build it and post pictures so we can all slober over them! If I'm outta line just crack the back of my skull ;)
#4

Jon, basically, all my scratch builds are dimensionally off from the actual dimensions… If I scale up from HO plans, it would need to be scaled up 3.06 times the HO scale drawing, and I only scale up 3 times, and the .06 gets left off… I don’t count rivits on my stuff, and don’t count rivits on anyone else’s railroad, either… Basically, if it looks prototypical at 10 feet, it passes muster…

#5

I go by ‘eye’, if it looks okay to me, I’m happy. I use pictures a lot, then use something in that I know the size of to measure the whole thing with.

#6

Thanks - No I’m not trying to count rivets :smiley: Was just wondering if I was on the right track or getting carried away. I figured that eights were a big enough measurement that it would be easy to hit, but when carried out to scale it usually was within an inch.

I’ve always liked Kevin Strong’s semi-metric method for 1:20 where 1 Foot = 15MM. That makes it simple to get within 4 inches (5MM) without having to think using a CM scaled ruler.

BTW - This is going to be a cooperative effort. Tank resizing has been out-shopped to the WV&K. Bart will be working up a method to lengthen the tank. The flat will be built in the CVSRy shops.

Hopefully, this project will actually get done. My shanty never got past the lexan box and that Stomper based speeder is still un-painted and un-detailed.

#7

Depends on what I’m working on. If I’m using a commercial product as a basis, then my tolerances are however close the commercial product comes to what I’m modeling, or how close I can reasonably get it. If I’m scratchbuilding something and have a good set of plans, I try to keep things as spot on as possible. The one thing to keep in mind, too, is that plans are often “off” by an inch here or there, too, depending on how things are measured. As Jon mentioned, my scale rule is a standard metric ruler marked into 15mm segments. Each 5mm segment is 4", so half of that is 2". One millimeter either way of the half-way point gives me nearly an inch, so I guess I try to keep things within a scale inch. Blending the two worlds–using commercial parts (cabs, tenders, boilers) with scratchbuilt components means a bit of fudging here and there, so there’s always a degree of “wiggle room.” If I’m scratchbuiling something where there are no plans, then heck–it’s as close as I can guess and that’s good enough!

Truthfully, as much as I lament about it during the building process, a year later, I can’t remember where the “errors” are, so it doesn’t really matter. I tend to look at my models through the camera lens. Actual dimension aren’t critical, but believable details are.

Later,

K

#8

Scales are for fish :wink:

Tolerance is for rude neighbors :lol:

I actually do try to keep things tight but as I’m often building by Eye to no plan whatsowever, I’m no role model.

#9

Like Vic and Jerry, I model ‘by eye’. To me a rule is a straight edge for cutting styrene. ‘Scale tolerance’ depends on what it is scaled up against or compared to. If it looks OK, then it is OK. I do prefer stock in a consist to have similar dimensions, as regards length, width, height and so find that adherence to scale looks somehow out of place. I feel that I have become exposed too much to the LGB ‘gummi’ scale rule, with the exception that I like my Bachmann coaches six inches longer than stock length. To my eye, the increased length looks more aesthetically pleasing.

#10

My ruler tends to get buried under all the other crap on my work space when I’m building something. :smiley:

-Brian

#11

I’m waiting on my Scale Card Rulers to be delivered today…since I know very little about “real” trains…I try not to get too caught up in the whole ordeal…I do want things to mesh nicely with each other-hence the upsize of the flats to “look better” with my Fn3 locos…

For the kids-anything goes, as long as it’s built tough…!!

cale

#12

How about scale 1/8" :smiley: :smiley: :smiley: :smiley:

I do use my Scale Card ruler when I measure things, but it’s usually just to insure that parts are the same size. I find it handy to know that my window is 4’6", for instance.

I typically don’t scratch build to a scale model; usually I just let the models inspire me and I build it to what looks good.

#13

Another thing to remember is that when you have drawings for a certain type of boxcar or whatever, that those drawings are generally based on ONE prototype car that was measured. Cars were rebuilt all the time with different size parts.

#14

My tolerance is the 10 foot rule…
But having said that, does anyone have, or know of, a down- loadable, printable, 1:20.3 conversion chart?

#15

I dunno about any chart. I use Bob’s friendly calculator http://www.largescalecentral.com/scalecalc.php

That and the CM ruler method Kevin mentioned above. I just haven’t gotten around to marking mine off every 15mm yet :slight_smile:

#16

I really like my rulers from http://www.thescalecard.com/ They’re clear with black lettering and markings. I have a 2’ one, as well as several of the 6" ones. Once you use Bob’s calculator, you can easily transfer the dimensions to your model.

#17

I have used Bob’s scale calculator on more than a few occassions… I also use a scale ruler made by CTT Inc… It is also clear with black print and flexible, and it’s a foot long…

#18

The Scale Card recently announced the availability of a 12" long scale in addition to their 6" and 24" product. The 24" scales allow measuring the full lengths (up to 40 scale feet) of most cars to the same accuracy as shorter distances without combining the measurements. The short 6" (10 scale foot) scale is great for bench work. The low cost allows for them to be cut up to permanently use on special applications such as building jigs, choppers and saws.

The 1:20.32 scales are marked in 1" divisions. This means the theoretical precision one can achieve is nominally 1/2", but good craftsmen can do somewhat better than the accepted theoretical precision. Not required, but nice for the “museum quality” builder and very useful for us “that’s close enough” hackers.

The Scale Card also has pocket sized “Scale Cards” that are extremely useful for checking the size of all sorts of things in stores and in the wilds. I usually carry my 1:20.32 one. They also have scale to scale conversion cards, although I usually just use a calculator.

I have no connection to The Scale Card, other than being a very satisfied repeat customer.

For many items such as buildings and bridges, I round off the scale factor to 1:20 rather than 1:20.32. The difference is ~1.6%. Absolutely not a significant difference for stuff planted in the great outdoors. If I build something really detailed or precise (which is rarely these days), I then use 1:20.3 as the conversion factor along with shop measuring tools such a digital caliper. But I still usually go to the closest available ‘standard’ size material.

I agree with Jon’s original statements about tolerances: A 1 1/2" deviation in the length of a 24’ car is nothing. That same deviation in a grab iron would be unacceptable.

Happy RRing,

Jerry

#19
Kevin Strong said:
Truthfully, as much as I lament about it during the building process, a year later, I can't remember where the "errors" are

Later,

K


I cannot tell ya’ how truthful this particular comment is! I spent 12+ years restoring an old home and about 1/2 way through the process I learned this. On my current viaduct project, I reflected back on what I already knew. Several mistakes made cutting and measuring however now that it’s coming together it goes totally un noticed. Once again it’s all in how the eye travels and what are the main focal points.

Cale,
Your words on building it tough for the kids is spot on.:wink:

#20

Depends on what I’m modeling, what construction materials are available, and what reference material I have.

Building something from no specific prototype, I’m not too finicky. If the construction material I’m using isn’t available in the required dimensions, I’ll use whatever is close to the dimensions I want. If I have good reference (photos, drawings) with measurements, I’ll get as close as possible. If not, I just go by what looks “right”.