Q. Other manufacturers sell 75 mm motors and yet Loki has 76 mm motors. Are they the same? Will they fit my rocket?
A. 75mm cases are the same OD as 76mm or 3" cases. The standard motor case OD for all of these is 2.985". 76mm equals 2.992" while 75mm equals 2.952". Round up the case OD by .007" and you get 76mm. So, 76mm nomenclature is a more accurate conversion.
Q. What sizes of O-rings do Loki Research motors use?
A. See the O-ring chart in the tech info section.
Q. What material O-ring should I use?
A. Silicone, Viton, and Buna-N are all acceptable. Silicone works best on graphite nozzles as they are MUCH easier and quicker to clean off the graphite after being heat soaked.
Q. Where can I buy replacement O-rings?
A. You may purchase them directly from Loki Research. McMaster-Carr is another excellent source. Your local hardware store may stock some sizes. Be careful! You must use the correct size O-ring! "Close enough" is NOT good enough!
Q. Can I re-use my O-rings?
A. The O-rings from a motor can often be reused, particularly those on the forward bulkhead as they generally do not get very hot. Inspect them very carefully for cuts and cracks, and replace as needed.
However, we don`t recommend reusing any of them, as new O-rings are cheap and an O-ring failure will usually destroy your motor hardware and possibly the rocket as well. This is not a good place to cut corners.
Q. What type of snap ring pliers should I buy and where can I get them?
A. Knipex brand snap ring pliers are recommended. These may be purchased from www.mcmaster.com. Use part number 5449A92 for 38mm and 54mm motors, 5449A93 for 54mm and 76mm motors, and 5449A94 for 98 mm and 114 mm motors. The 5449A92 part will also work for 29mm rings if you file the tips a tiny bit.
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