Calculator blog

Musings and comments about our common interest


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Considerations on leather cases: the HP41c


Coconutfundas_-_6We have lately commissioned a couple of calculator cases for Voyager and Pioneer calculators. These cover many of the most used calculators, and we plan to extend it to other calculator ranges. Clearly now we need to address the HP41c range. Old vinyl cases are quite expensive nowadays - around 35€ for the whole length case.

When discussing with the leather technicians, I learned that the original HP41c vinyl case is a quite complicated case to build. As it has a relatively short zipper, it is quite complicated to assemble and requires a technique that was well known 50 years ago, but that fewer and fewer artisans master now: it is called "wood block". It is very similar to assemble luxuty leather shoes - but it explains also why later cases were shorter and had wider zipper mouths. It also has black ribbons in the corners - which makes it also more expensive to makeAnyway, the price for a complete leather HP41c long case was prohibitive. 

If we release the short zipper limitation then other techniques may be used and the price is substantially lower. Also the perimetral ribbon makes it more expensive - but let's see what the final cost is. 

The second question is whether it makes sense to produce the long case (for which we already have the foam sponge!) or go directly to the smaller, HP41c sized units. Probably we will end up with both. Color will be dark brown to start with. 

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More about: HP41c case
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Sponge for HP41c case

Most of us have our HP41c in the original vinyl case. For some reason, this case was made big enough so that the calculator could be stored together with the card reader. This was done under the assumption that a significant part of the users would buy the card reader - which may have happened at the very beginning but definitely not later on. The serial numbers of the card readers that I receive are typically from before 1982 - so that may be the reason. Anyway, all cases were long, except from some cases like the one on the right that may have been made for another calculator.

For those users that had not bought the card reader, HP included a yellow sponge to pad the calculator into the long case, so that it didn't "dance" inside the case. These sponges are now quite old, and have taken a "greenish" color. Many of them have been contaminated with the dust coming from the degradation of the internal lining, and some of them are lost. We have commissioned a sponge from a foam producer. It is white but nevertheless the right size and texture. Not worth an order (just 1€!) but worthy to complete the one you already prepared!



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True leather case for the HP12c

We have ordered the first production batch of leather cases for the Voyager family of calculators - including the HP12c and HP15C.

The original vinyl cases of the early HP12c were very resistant - as well as the early Pioneer units (HP17bII and HP42s and the like). However, later versions were made of PE-leather, which is much less resistant than vinyl. I have several cases of HP15c Limited Edition and HP12c Anniversary Edition and both have a very bad aspect after 5 or 6 years of normal use. I will not post here pictures of said cases, lest anyone identify these cases with our new product.

Our plan is to contact all the customers that have bought a HP15C from us to offer the premium leather at a discount in the first place. It will be 25€ shipping included - everywhere in the world. Then we will offer the case to the rest of our customers.

The initial batch will be in black leather. However, we are testing other colours like brown and burgundy. First, black; then other colours. 

By the way: anyone interested on true leather HP41C case? 

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True leather cases?



We are planning to introduce three leather cases for the most typical HP calculators. We will start with:

  • The ubiquitous HP41 case. We will use the exact same shape as the one we know. We are using as template the original one, loaded with a 41c+card reader, to make sure it fits. We will have to find also the yellow sponge for those that do not have a card reader.
  • A Voyager case (hp12c, hp10c, hp11c, hp15c, hp16c). The original case was in vinyl, but later versions were in PE and had a very bad behaviour - including the anniversary versions of 12c and 15c. There have been previously leather cases by HP very well made, with a burgundy leather external and a cream leather internal, with upper cover; but it was so nice and thick that it could not really be used for your jacket pocket - which is for me the original intention of the Voyager line. (also the later HP12c Platinum units were far too thick for jacket use)
  • A Pioneer case. This is also a thin calculator that can fit in a jacket pocket. I don't know who was in charge of selecting the cases for the latest HP17bII+ - again, they won't fit comfortably on the jacket pocket. 

The key for both the Voyagenr and Pioneer cases is that they fit quite tight - and do not slip out immediately. Normal fabric is ruled out, while suede- or felt-type may work well. Also, in my opinion, the suede-like feeling of the inner part of a leather may work, too.

We will keep you updated. Meanwhile, let me show you 4 different types of HP41c covers, 


And also a Voyager Burgundy leather case, and a similar case for the Clamshell type:


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