Hullavator Gas Spring Replacement (simplified)

Transcription

1 Hullavator Gas Spring Replacement (simplified) Some Thule Hullavators came with (original owner) lifetime warranties if you are the original owner of a defective Hullavator and can provide proof of purchase you should consider contacting Thule to discuss possible remedy under warranty. Disclaimer: Hullavators were NOT designed for gas spring replacement by the user. Gas springs contain a gas under high pressure and exert major force concentrated in a small area therefore serious injury or damage to property can result from attempts to undertake repairs or replacement. The article below is for informational purposes only; the author assumes NO liability for any injury, loss or damage suffered as a result of the use, misuse or reliance on the information and content in the following article. Anyone undertaking gas spring replacement assumes full responsibility for possessing the required knowledge, skills and equipment to safely undertake any repairs or replacement of parts. Description The Hullavators (Model 897xt) described in this article were purchased in early 2008 and were used frequently for 8 years until one of the gas springs failed (lost pressure). One of the gas springs that had not failed was sent to Gemini Gas Springs Inc. in Vernon B.C. for identification and subsequently new gas springs were purchased (described by Gemini as 8/ /500N M8/M8 ) for less than $25 each plus shipping (2016). These gas springs exert a force of 500 Newtons (112 pounds-force). Replacement of gas springs should be done for both Hullavators in a pair to keep them in balance when lifting a kayak. Executive Summary: one rivet (axle) was drilled out; the old gas spring was removed; a wire rope/turnbuckle compression harness was made; the barrel end of the replacement gas spring was installed and the compression harness was used to compress the replacement gas spring in place in the Hullavator and a bolt (the replacement for the removed rivet) was inserted to fix the rod end of the replacement gas spring. A description of the tools and materials used are listed at the end of the article. Detailed description: 1. The hull cradles were removed from the base (arm assembly). 2. It has been suggested that to ease the removal of gas springs that still have gas pressure (and therefore are still exerting force) a small (1/32 ) hole could be drilled in the barrel to release the gas pressure. Reportedly the industry does this deflation prior to disposal. If this approach is used utmost care is necessary. Always wear safety glasses, hearing protection and a filter mask. The escaping nitrogen gas is itself harmless but is under high pressure and may carry some residual lubricating oil or other debris as it escapes. The work area must be ventilated. Always drill from above with the gas spring positioned horizontally as then most of the residual oil will be in the lowest part of the barrel. Once the gas has escaped remove any oil by pushing in the rod and then dispose of these materials according to local regulations. In the approach described in this article the gas pressure was NOT released by drilling prior to removal step 3. below was used directly.

2 3. Note: Hullavator gas springs screw into an eye fitting at both the barrel and rod end (right hand thread). With the Hullavator in the closed position and bottom side up, the original gas spring was separated from the eye -fitting at the rod end by unscrewing the rod (right-hand thread) using needle-nose vice grips on the rod (photo at right). Slight downward pressure was applied while turning the rod and when the rod was fully unscrewed the fitting rotated downward and the rod separated from the fitting and the rod extended approx. 2 (This photo was actually taken, for illustration purposes, after the replacement gas spring was installed). 4. The rivet (axle) fixing the rod end of the gas spring (photo at left below) was drilled out at the flared end of the rivet using an 11/32 drill bit. Only one rivet needed to be drilled out. The rivets are 5/16 (8 mm) and are HARD steel which makes this removal somewhat challenging. The rivet tended to spin with the drill bit so soft (copper) wire was carefully wrapped around the rivet between the Hullavator outer shell and the black plastic spacer surrounding most of the rivet (photo at right below). The Hullavator was clamped and a drill press was used care was taken to not damage the Hullavator outer shell. The rivet was then pushed out taking care not to damage the black plastic spacer (visible in photo at right below) that was around the rivet as this spacer is required for proper re-assembly. 5. The articulating plates were now hinged apart and the barrel end of the original gas spring was unscrewed (right-hand thread) and removed and the barrel end of the new gas spring was screwed into the fitting. (The photo at right shows a new gas spring in place.)

3 6. A compression harness was constructed (photo below) parts were available at a local hardware store. Approximately 36 of 1/8 wire rope with appropriate sized crimp sleeves and cable clip(s) were used. The turnbuckle shown below was nominally 9 3/8 (fully extended) and had a take-up (change in length from fully expanded to fully closed) of 2 ½. Steps in this approach that follow would be easier with a turnbuckle with a take-up of 4 (i.e. with a nominal length of approx ). The turnbuckle must be rated for a load of at least 150lbs. More details follow. 7. Two aluminum crimping loop sleeves were used (as they are very compact) to form a loop on one end of the wire rope. The loop was kept small to make later compression (turnbuckling) easier. The aluminum sleeves required considerable pressure to fix the wire rope in place. Plastic coated wire rope (which was on-hand) was used and found to slip in the crimp sleeves so it was necessary to remove 6 of the plastic coating at the crimp sleeve end. Note the nail taped to the waist (groove) in the sleeve in the photo below - a 4 vice was used (right photo) to compress the nail into the waist of the sleeve. There are special tools ($$) made to compress these aluminum sleeves. (The threaded cable clip was NOT installed at this point.)

4 10. N.B. 8. As noted, the gas springs thread into an eye fitting at both the barrel and rod end. These fittings have a square shoulder (right photo below). A noose was constructed (from clothes hanger; more detail below) to slip over the fitting on the rod end of the gas spring. The photo on the left shows a noose slipped over the fitting to test for snugness. 9. The steps in forming the noose are shown below. This noose had to be formed so that it was snug on the shoulders of the eye fitting otherwise when under load it slipped over the shoulders of the fitting and down around the rod. Approx. 9 lengths of steel clothes hanger (1/16-2 mm diameter) and needle-nose pliers were used to construct the noose. A vice provided a valuable third hand for shaping the noose. The noose was then hooked onto the loop (made in step 7) at the end of the wire rope, crimped and taped securely (see the second photo below). The wire used to form the noose needed to be of sufficiently small diameter that the black plastic spacer (which was removed with the old gas spring and which keeps the rod end of the gas spring and the bottom plate centered in the assembly) could be re-installed while the noose was still in place and the harness was still compressing the new gas spring.

5 11. One 2 ½ x 5/16 carriage bolt, two 5/16 nuts and two large 5/16 ( fender ) washers were tightly attached to one end of the turnbuckle. (photo below) 12. The Hullavator was now securely fixed to a solid working surface in this example it was clamped in a wood-working vice. 13. The foam bumper located on the bottom plate was removed so that it would not interfere with the turnbuckle it was later replaced with a piece of foam (from a flip-flop ) cut to the same size and glued in place. 14. The eye fitting that had been removed from the rod end of the old gas spring was screwed onto the rod end of the replacement gas spring. (photo right) 15. The noose end of the harness was slipped under the rivet that holds the articulating plates together (photo below) and then up alongside the gas spring (between the articulating plates) and the noose was placed over the end of the eye fitting on the rod end. (photo at right ignore the gold-colored bolt). The turnbuckle was placed on the bottom plate with the carriagebolt-end placed in the cut-out in the bottom plate. The free end of the wire rope (shown with green tape) was formed into a loop using a screw-type cable clip and hooked onto the turnbuckle. The cable clip was not yet fully tightened.

6 16. The free end of the wire rope was clamped with vice-grips and pulled toward the Hullavator release handle end (to the left in photo above) to remove as much slack from the wire rope as possible (an assistant is handy here) and the cable clip was then securely tightened on the wire rope. (Using a nut driver in a cordless hand drill.) As shown an approx. ¼ thick shim slipped under the turnbuckle hook (photo above) this made tightening the turnbuckle much easier. The other end of the turnbuckle was already elevated by the carriage bolt. 17. The turnbuckle was slowly tightened until the hole in the eye fitting lined up with the holes in the end tabs of the bottom plate the alignment was confirmed by inserting the replacement bolt - first just in the plate and fitting (left photo below) and then in the Hullavator shell, the plate and the fitting. (right photo below). The turnbuckle was carefully adjusted so that the bolt was as well centered as possible. If the turnbuckle had insufficient take-up to bring the parts into alignment tension was released (using the turnbuckle) and step 16. above repeated with more effect as the wire rope had now been formed to the task. This was mainly an issue when the wire rope was first used. 18. Comment: In the photos above the noose was placed so that the wire rope harness was below (on the floor side of) the gas spring. Alternatively the harness can be placed between the gas spring and the bottom plate. Both approaches were used and assembly was somewhat easier in the second case with the harness between the gas spring and the bottom plate (this configuration is not shown). 19. The bolt was removed and the black plastic spacer (that was removed earlier) was placed around the end of the fitting and the two end tabs of the bottom plate. (This spacer is necessary to keep the rod end of the gas spring and the plate centered in the assembly.) The bolt was then reinserted some wiggling was necessary. Great care was taken to keep fingers away from the end of the fitting in case the noose slipped. The bolt threads proved useful to advance the bolt through the assembly by turning the bolt but this only worked if the alignment was good. Once the bolt was fully in place a nut was installed (locktite was also applied). Care was taken to not tighten the nut so much that the plastic spacer was binding in the housing as all the original rivets in the Hullavator were slightly loose in the housing to allow for rotation of the spacer.

7 20. The turnbuckle was loosened to release the tension on the wire rope and then the noose over the eye fitting at the rod end was carefully cut with a pair of cutting pliers. The noose and the entire harness were then slipped out from between the articulating plates. A new noose is needed for each gas spring replacement. 21. The stub end of the bolt was hack- sawed off flush with the nut and then the end filed smooth. 22. All done - now onto the second one! Materials Used - 36 of 1/8 wire rope - two (1/8 ) aluminum crimping loop sleeves - one (1/8 ) cable clip - clothes hanger - one 2 finishing nail - 6 of 14 gauge copper wire - one 9 3/8 turnbuckle - ¼ wood shim - Locktite - one 4 x5/16 bolt and (nylon insert) nut - one 2 ½ x5/16 carriage bolt, two 5/16 nuts, two 5/16 fender washers Tools Used - 4 vice - woodworking vice - vice-grip pliers - needle-nose pliers - two small wrenches (for 5/16 bolt) - drill (press) and 11/32 drill bit - hack-saw - cutting pliers - nut driver (for 1/8 cable clip) - cordless drill