De-icing . . .Soft PVC . . .Water filtration . . .
Dear Search Engineer: I am looking for information on companies that have experience with anti-icing solutions to eliminate the ice build-up on the power collection assembly of an elevated transit system. When operating in the New York/New Jersey winters, the spring-loaded, pivoting swing arm current collector assembly becomes ineffective due to accumulating ice. We've looked at electric heaters (too much current draw), spray de-icing solutions (drips on traffic below), and fabric covers (restricts the swing arm motion). The preferred solution would be a custom-molded flexible, durable, non-conducting bellows-type cover.—R.L. in NY
Hey, R.L.: NASA Glenn Research Center in Cleveland has an Icing Branch that studies anti-icing. Check it out at http://rbi.ims.ca/3855-511.
Dear Search Engineer: I need to assemble two parts made of soft PVC, to withstand peel strength of at least 5 kg/cm2.—R.P. in MA
Dear R.P.: Loctite's 401 Cyanoacrylate is a good product for bonding PVC, providing your gaps are less than 0.005 inch when assembled. Loctite 454 is the gel version of this product line and is good for porous surfaces filling gaps up to 0.01 inch. Both have fixture times of less than 20 sec. On soft plastics or rubber, these products will often show substrate failure in peel forces. If the gaps are bigger than 0.01 inch, then I would suggest Loctite Speedbonder adhesives that, when mixed, can fill gaps up to 0.05 inch and come in fixture times of 2-25 min. Check out http://www.loctite.com for more information.
Dear Search Engineer: I am designing a water filter to be immersed in river water for an extended period. We are concerned with marine organisms attaching themselves to the filter element. Is there any inhibiting material that could be alloyed with an injectable thermoplastic? —S.Z. in MA
Dear S.Z.: Antimicrobials inhibit the growth of mold, mildew, fungus, and bacteria, and would increase the life of this filter. RTP Co. (http://www.rtpcompany.com) is a custom thermoplastic compounder that can compound antimicrobials into a number of resins. They also have FDA grades available.
Dear Search Engineer: I need to make cylindrical torpedo tubes with a diameter of 3 inches at both ends and 5 inches in the middle. The diameters vary parabolically. Shaft length is approximately 72 inches and is made of aluminum Al-6061-T6. We need to make about 10 parts for prototypes. Any way of making this part for under $20K in one piece without degrading the properties of the Al?—M.K. in MI
Dear M.K.: Talk to a quality machine shop with CNC machining and ask an Aluminum casting facility. This alloy is weldable, so you could make it in halves and join together. The joint could be longitudinal or transverse. In latter case, a ring could be press-fitted around the outside to reinforce at seam. And then the ring can be ground flush—so as not to disturb fluid flow patterns that you may be testing. Laser welding is another option to investigate. However, getting 10 parts for $20K seems a tad optimistic.