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Help interpreting Muir-Mackenzie Strad poster


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I'm working on a scroll template using Roger Hargrave's measurements of the Muir-Mackenzie strad given on the back of the poster. The turns of the scroll are pretty well defined using the measurements he gives (I averaged the left+right side measurements where there were discrepancies - all were minor differences). There are 4 measurements given that help define the side profile of the pegbox walls into the chin (see attached). I'm wondering if anybody has any guidance for the best way to interpret some of those.

The 18mm measurement is the one I'm struggling with the most - it only has one arrow so it's hard to know for sure what it is measuring between. The throat and the outside of the scroll at a roughly 45 degree angle? Any thoughts/ideas here are much appreciated.

The 16.5mm measurement I'm interpreting as the distance perpendicular to the fingerboard plane from the point farthest from that plane to the point where it intersects the inside of the throat. Sound right?

The 24mm distance I'm interpreting as the distance perpendicular to the fingerboard plane from the point where the pegbox walls begin to curve away from that plane. It's hard to know exactly how far that point is from the nut, but I can use the photos for that I suppose.

Any other guidelines or measurements I can use to define the template further would be greatly appreciated (especially measurements that help fix the chin/pegbox walls in place). The backup plan is to just fix template lines based on the photographs but I'm worried about parallax / perspective effects introducing errors into the template. I'd prefer to work from measurements wherever possible instead. When comparing the drawing of the scroll turns based on Roger's measurements to the photographs it is clear that parallax is a significant issue and that measurements are preferable.

Once I'm done I will make the cad drawing available for others. When it's finalized I will potentially have it laser cut if anybody is interested in that as well.

IMG_2219.jpg

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The diagram you illustrate is just Rogers template for recording measurements on any violin, no resemblance to the M-M Scroll. I was one of the surfs charged with measuring it. We just measured the lengths with a vernier caliper at the points indicated on his template. The 18mm is the measurement from the end of the throat to the outside of the peg box, measured with a caliper. The 24mm is where the curve of the back profile is at it’s deepest. A template is just a starting point. Once you have cut that out, you have to use your eyes and the original photo

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I think that the two measures 18 and 16.5 are swapped places, a printing error.

18 mm is the width measured as indicated by the double-headed arrow, 16.5 mm is the width at the end of the pegbox, measured with the caliper at the point indicated by the single arrow, resting the caliper on the right and left sides at the junction of the pegbox at the throat.

This way the measurements are more fitting with those of the majority of the Stradivarian heads.

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@jacobsaunders thanks! I figured the diagram was just a placeholder to show measurements - I started my drawing of the template from scratch and am trying to constrain it as much as possible from the measurements before relying on photos/eye to complete the template. Your explanation of the 24mm measurement definitely helps - I was interpreting that the wrong way.

 

@Davide Sora thank you! (and while I have you thank you for sharing all of the great videos). So the measurement that only has one arrow is actually meant to read the width across the sides of the pegbox - that explains what happened to the other arrow! :D. Interesting suggestion about the printing error as well! I'll play around with both and compare against the photos to confirm

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Here is the template I have so far, overlayed in green against images of the left and right side of the scroll. I'm pretty happy with how it's shaping up so I'll probably finish up with the rest of the neck/root and call it done. The biggest discrepancy is obviously the peg placement but I decided to use @Matthew Noykos's algorithm from here to lay those out instead of copying from the image.

@Davide Sora I think this scroll must just be an outlier w/ respect to that measurement from the back of the throat - the 16.5 printed on the poster seems to do a better job fitting the images than swapping it with the 18.

If anybody would like an SVG of the template please just let me know, I'd be happy to post it.

 

scroll-left.jpg

scroll-right.jpg

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In my opinion your model has two "critical issues":

1) I do not think you have taken into account the consumption of the bevels especially on the back and front of the volute, which in Muir Mackenzie are quite relevant (see photo)

2) the spiral does not have a regular trend, in the sense that it does not continue to tighten from the volute towards the eye, it seems tighter in the lower part near the throat and tends to widen when the spiral enters the volute. This could be the case albeit to a lesser extent in the original head, but I believe it is mainly due to wear near the throat or a "mistake" by Stradivari that has removed too much at that point compared to its original model which better shows his theoretical intent (see photo)

I see these details from the point of view of a modern maker who aims to reconstruct the original model from which that head came out, if instead the intent were to make an exact copy of that scroll the considerations could be different.

256475315_MuirMackenzie1694scroll.thumb.jpg.f3c12ce4798e1c0b1da2a10e7ceee66c.jpg466323942_DSC_4012TCritrid_Disegnostradoriginale.thumb.jpg.86f9072f95987655aadb5c591222e6db.jpg

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Thank you @Davide Sora! It's interesting that both of those issues you point out are with the volute/turns - that was the part of the drawing I was more confident in since it comes pretty much directly from the measurements on the poster.

I definitely noticed what you pointed out in #2 regarding the unevenness of the spiral as it enters the volute from the throat. I think that comes down to the philosophical question that has been discussed on this board many times - is it better to copy an instrument flaw-for-flaw or is it better to copy the intent of the maker? I think in my case since I've already decided to make one template averaging the dimensions of each side of the scroll it probably also makes sense to try to correct for things like that.

With respect to #1 do you think the correct solution is to make the template marginally larger than the numbers given on the poster so that when the bevels are added it approaches a match?

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Of course the measures on the poster are relative to the object, that is the scroll in its current worn state. Originally they will have been slightly wider in places where there is wear. Understanding how much to increase the measurements and how to correct the curves is not easy at all if you have no experience, a useful thing is to observe the widths of the bevel where it is little worn (visible black ink) and try to reconstruct it on the entire scroll taking as a reference the inside line of the chamfer where it is not worn, or by reconstructing the coherence of the curves according to the Stradivarian style (observing as much scrolls as possible from the same period of the maker) where even the inside line of the chamfer has gone away due to wear.

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