6 replies to this topic

[iceberg210]

Perhaps I have just had not enough stimulating conversation lately while riding lifts, or I've become more observant I'm not sure but lately I've started wondering about the differences in the tower heads used by the various manufactures. I searched around through the depths of the forums but didn't really find much so I figured I'd go ahead and ask my questions. (Don't quite know if this is a tech question or general but I kind of though technical so it find itself posted here, but if it fits better in the other forum don't hesitate to move it)

While I'm no industry insider I would assume that there would be some major differences and even preferences on one over another based especially on experience of the lift mechanics that use these tower heads to work on the lifts.

I've noticed specifically two general types of designs, one seems to clamp to the tower, such as the ones used by Thiokol and some Riblet ones as well.

Thiokol one on the former Powderhorn lift at Solitude Utah.



Riblet one on the Hodaq lift at Hoodoo Oregon.





The other style I've noticed are ones that bolt directly to the top of the tower such as Yans, Pomas, CTECs, etc.

Yan one on the Albion lift at Alta Utah.



CTEC one on the Supreme lift at Alta Utah.



I was wondering if there were any particular advantages or disadvantages to the two designs, either in reference to installation or maintainence of the lift.

The other thing I was wondering about is about the lifting frames on the tower heads. According to everything I've read in the ANSI standards they aren't required, however every new lift you see these days have them it seems. Is this just a case of they being so convenient to have on each and every tower, unlike the portable ones that you had on the old Riblets and such) that the extra cost to build lifts with them is worth it in ease of maintainance?

Anyway thanks for reading and thanks for any information or thoughts on the subject.

This post has been edited by iceberg210: 27 December 2009 - 09:33 PM

[Andoman]

I think part of this is at the time thiokol and riblet (I believe Hall did this also) were producing lifts (60s, 70s, 80s) steel was a cheap commodity and mass producing a single size pole that could be adjusted to size in the field lowered cost. However, now with commodity prices through the roof it's cheaper to custom build each pole to the correct size without giving away extra steel. This is the opinion of someone that has worked with the steel industry not the lift industry (other than running lifts during college and from time to time during the holidays to make some extra cash) so it's just a guess I'm sure Dino or Emax will chime in with the correct answer if I'm wrong .

[monkey]

I would have to say ease of installation, most helicopters can only lift sections of a tower as a modern HSQ tower head has allot of beef to it. As the tower loads on a 82' thiokol double are significantly less than on a 02' HSQ. Tower heads can be assembled in the parking lot and flown into place and "simply" bolted on to the top of the tower while the ship hovers over head. Having one design from doubles to six-packs reduces cost. Now as far as lifting frames not having to lift a portable lifting frame and couple of chain hoist onto every tower makes life a lot easier and faster.

[Lift Dinosaur]

My $0.02
Both Andoman and monkey are correct. In the old days pipe was cheap and Engineering wasn't done by a computer program. Access to tower foundations was often provided by a "Dozer" pioneering a route to the tower location for a crane or boom truck to set the tower. Double and triple chairlifts towers had half the weight of modern detachable equipment. It was easy to make a standard height tower with foundation and then adjust the crossarm elevation for correct loading.
YAN towers had the crossarms welded to the top of the pipe with a cap plate. The towers were built in "random lengths" (pipe was bought in "random 36, random 42, etc)and after the angle iron was placed in the bottom of the foundation hole and surveyed for elevation, the pipe was cut to the correct length at the bottom.
The limiting factor today is limited access to tower locations and what a given helicopter can pick at a given elevation.Most components are design/limited to about 4500-5000 lbs. This is why you see 3 stage towers, crossarms set with no assemblies, and individual assemblies being flown to the tower location.
Off to dinner - more later if you have questions.

Dino

[william b]

Regarding the rope picking apparatus on towers, I believe that the current B.77.1 standard requires that fall protection attachment points be provided, and they must be above the working height (crossarm height). Possibly the manufacturer's thinking is that if they need to provide this, then the added expense of making the structure suitable for rigging is nominal.

wbl

[Lift Dinosaur]

Lifting Frames / Lifting Gantries / Lifting Arms:
These devices came of age in the early '80's.
Prior to this time Lifts had some common characteristics: relatively low tension (less than 30,000 lbs); shorter tower spans (less than 150-200 feet); more towers; less sheaves per assembly; small cable diameters (1 1/4" or less); and double chairs (with triples becoming very popular).
Triple and Quad chairs ushered in the need for: higher tension (up to 60,000lbs); larger cable diameters (1 1/2" to 2");longer tower spans (up to 300');less towers; and more sheaves per assembly. With all of this added hanging weight, it was necessary to have an Engineered system of picking up the haul rope for maintenance and repair work rather than relying on an "A-Frame" or "Gin Pole" that someone had made back in the Vehicle Maintenance Shop.

Dino

[liftmech]

Lifting frames :
Gin poles and A-frames:
Somewhere to tie off to that doesn't result in tripping over one's fall-protection: priceless.