Robert Holmén's poll made me curious about actually taking this measurement, so here's what I tried: I taped a paper yardstick (or if you prefer, a 0.9144-meter stick) to my wall with the "zero" tick at the same elevation as my embouchure. Standing a slide-length's distance from the yardstick, I held my trombone in playing position with the mouthpiece bore aimed at the zero. I then slowly (about 1 inch per second) pivoted the trombone downwards and noted the inch marker when the slide started to move. The number of inches below horizontal was the measurement we're interested in, "declination". The smaller the number the declination when the slide starts to move, the better the slide. Really good slides should start to move with a small pivot downwards. Rougher slides will require more declination to get moving.
My testing equipment:
A stock mid-1990s Bach 42BO.
Interior of slide outers cleaned with cotton-wrapped rod.
Exterior of slide inners wiped with cotton rag.
Rice grain-sized amount of Trombotine applied evenly to each slide stocking.
Slide pumped ten times each in North, Northwest, East, Southeast, etc. around the compass.
Wiped excess Trombotine off slide stockings with cotton rag.
Spray with atomized tap water.
So how slidey was my slide? Pretty slidey, but probably could be better.
slide_declination_data_2022_Nov_.jpg
In nearly all cases, the slide was easier to move from 1st position (red) compared to 3rd position (blue). In fact, the profiles are so similar that I'll only talk about the 1st position data and assume the other positions are progressively worse. I began my experiment just before my typical slide lube application. The data point to the left of the first dotted gray line at -0.5 hour shows that I had to pivot my horn 9 inches below horizontal to get the slide to move. Immediately after applying Trombotine (leftmost dotted gray line), slide action improved dramatically, needing only a 4" downward pivot. For 5–6 hours of playing after Trombotine application, slide action was pretty consistent in that I needed to pivot 4–6 inches (approx 10–16° declination). As I played an additional 6 to 12 hours, the amount of additional tilt I needed accelerated towards 9–10 inches until I re-applied Trombotine (rightmost dotted gray line).
All those observations are about what we'd expect. What interests me most is that slidey-ness can be easily, quickly, and cheaply measured and reported with a single, simple value that is straightforward to understand.
I hereby propose the
Robcat Slide Slidey-ness Index (RSSI). Tape a ruler to the wall, clean and lube the trombone slide, and measure the inches of downward tilt required to get the slide to move from first position. This number, reported in inches, is a fairly objective measure of slide action. The smaller the number, the slidey-er your slide is. Using my slide as an example, the relevant datum is the red dot indicated by the arrow. I would say, "For this trombone slide, the RSSI is 4 inches."
If the trombone community adopts some standard along these lines, we'd see benefits in at least a couple of areas. First, we can better judge when a trombone slide needs professional adjustment/repair and how much improvement resulted from such a repair.
Q:
Should I send my slide in for repair?
A: Measure your slide's RSSI; it's easy. If you measure RSSI more than ___ inches, send it off to the tech.
This would be especially helpful advising less-experienced players over the internet.
Second, an objective measure of slide action would help convey accurate information between buyers and sellers. Browsing the classifieds here on TromboneChat, we see the listings pronounce something like "slide action is 8.5/10". All the ratings seem to be clustered up towards 10; rarely do I see a rating less than 7/10. What does it take to earn a 5/10? Slide moves halfway and stops? What's a 0/10? Frozen stuck? Was there a day as a music major in college when the professor tells the trombone students how to rate slide action on a scale of 0 to 10? Not to mention how to make that judgment consistently over a period of years. Instead, one could say, "Beautiful Conn 8H for sale. Great condition. Slide is 3" on the RSSI."
I would love to see the results if some of you could take the time to grab the best slide from your stable, give it a one-to-ten rating, and then measure its RSSI. Then we could see if this idea has any merit.
