In 1982 I was lucky enough to be in Europe for a few weeks on business. One weekend I drove to Reichenbach, Switzerland to meet Walter Marti, the designer and manufacturer of the Jumar ascender. Mr. Marti shared a great deal of information with me about his ascenders while his secretary, Mrs. Baumann, translated. Both Mr. Marti and Mrs. Baumann were very friendly. One of the most impressive things I learned during the visit was that there are many, many variations of Jumar that have not been put into commercial production. For example, I saw Jumar cams with the same "Z" shaped teeth found on the early Clog ascenders. (Does anybody have a pair they are willing to trade?) The coverage presented here is by no means exhaustive. As usual, I will only describe those models I own.
Incidentally, the Jumar is named after Adolph Jusi and Walter Marti. Jusi was studying eagles for the Swiss Government, and needed an ascender. Marti developed the Jumar for him.
The classic movie
"Godzilla versus Gigan" (Godzilla versus Gigan,
Toho Co., Ltd., available on New World Video) shows a Jumar
look-alike being used by the good guys in a successful escape
from the Godzilla tower where they were being held captive by
the cockroach space aliens. Their escape technique is shear nonsense,
but I'm intrigued by the ascender. It appears very similar to
a Jumar, but the casting differs in several respects. This looked
like either a version of the gray Jumar that I've never seen,
or a Japanese copy. For years I wondered if it really existed,
but in March 2008, Carlo Bellestrero sent me a page form an early
1970s Snell Sport Chamonix catalog that showed the ascender: it
is a Japanese copy of the Jumar that weighs 310 g. (versus
250 g. for the Jumar). Are there any readers who help me
acquire one of these ascenders? Please email
me if you can help!
[ Top | Version B | Version C | Version D | Return to H.E.C. Ascenders ]
I acquired my Jumar, Version A at the NSS Convention Auction in 1999. This is an earlier ascender than Versions B and C. Mechanically it is essentially identical, but the cams are color-coded instead of the safeties. Both safeties are anodized gold. The frame is painted with a speckled metallic gray paint instead of a uniform gray paint.
[ Top | Version A | Version C | Version D | Return to H.E.C. Ascenders ]
I acquired my Jumar, Version B on eBay from Karla Green in 2008. This is an earlier ascender than Version C. Mechanically it is essentially identical, but frame is painted with the same type speckled metallic gray paint as Version A.
[ Top | Version A | Version B | Version D | Return to H.E.C. Ascenders ]
I acquired this pair of ascenders used from Roy Jameson at the 1980 N.S.S. Convention. They were originally purchased in the early 1970s. I acquired a duplicate pair from John Yost in 1993.
The Jumar frame is an aluminum allow casting covered with a gray epoxy(?) paint. The frame has a rope channel cast into one side. The handle is roughly rectangular. A 21.6 by 13.8 mm. rectangular hole in the base of the handle provides access for the sling ropes. A triangular hole above the cam provides an upper attachment point for auxiliary slings.
The cam is a skeletonized stainless steel casting. The cam and cam spring are attached by a 5 mm. roll rivet. A steel washer keeps the roll rivet from pulling into the aluminum frame. The cam face is very well designed, with a concave surface whose radius decreases from top to bottom along the cam surface in order to compensate for different size ropes. The conical cam teeth are aligned perpendicular to the cam face. The tooth count is (4.5)^5(4.3)^4. The cam safety and safety spring are mounted on a 4.5 mm. pin located about half way down the handle. The cam safety is a piece of anodized aluminum, red for left handed ascenders and blue for right. This color coding has been maintained on all later model Jumars . The cam safety physically blocks the cam from opening far enough to allow the main rope to slip out of the rope channel. Rotating the cam safety towards the base of the ascender provides clearance for the cam to open completely.
The Jumar began to appear in American caving circles in the early 1960s, and has probably remained the most popular mechanical ascender since that time.
This model, like all Jumars, is very well made. All parts are finished, and there are no sharp edges exposed anywhere. "Gray" series Jumars are probably the easiest handled ascender to operate one handed. There is little if any difference in difficulty in using either hand. My technique is to open the safety with the middle finger, then open the cam with the thumb (of the matching hand) or forefinger (of the opposite hand). The entire sequence reduces to one fast, fluid motion with very little practice.
The major drawback of the early Jumars is the method provided for sling attachment. The correct method involves bringing the slings up through the square hole in the base of the Jumar and around the back of the handle. THIS IS NOT A COMPLETE DESCRIPTION SO DO NOT TRY THIS WITHOUT INSTRUCTION! It is unsafe to simply loop the sling through the handle, since this places the load on the thin, weak area at the base of the front strap. The front strap (brace) can then break under tension. There have been several reports of ascender failure resulting from this mistake (Davison, Don Jr., Hits and Near Misses, N.S.S. News, v 34, #5, May, 1976, p. 80; Davison, Don Jr., Hits and Near Misses, N.S.S. News, v 35, #4, April, 1977, p. 73). It is not clear whether the broken Jumars were Version A, Version C, Version D, or some other version. Eventually the 78 (yellow) series Jumar was developed to eliminate this perceived problem.
The color coded safety on the Jumar is nice, and suggests an even more practical idea: color coding one's left and right foot slings. Because of the universal availability of the Jumar, the red=left, blue=right scheme is an obvious choice. Petzl users might prefer a yellow left sling instead.
[ Top | Version A | Version B | Version C | Return to H.E.C. Ascenders ]
I acquired this pair of ascenders from Speleoshoppe at the 1976 N.S.S. Convention.
This Version is very similar to the previous one. There are some minor variations in the frame design. The rope channel is mounted lower on Version D, and so the force generated by the cam on the rope is more nearly centered. The area behind the cam leading to the rope channel was changed. Version A had a concavity behind the cam and a corresponding arch on the back side of the frame. Version C is flat behind the cam, and concave between two reinforcing ribs on the back side of the frame. "+GF+K9681" is cast in this concavity. The upper end of the cam channel is cast over in Version C, but in Version D it is open, and a stamped sheet metal cam housing is used instead. The handle area has been made smaller in depth. The details around the sling attachment hole are changed, with Version C being less bulky. The hole has been reduced to 24.5 by 10.4 mm.
The cam safety has been changed from aluminum to plastic, and is slightly smaller.
None of the changes mentioned seem to have a significant impact on any of the performance characteristics of the ascender. The only advantage Version D has over Version C is a slightly lighter weight.
[ Top | Version A | Version B | Version D ]
