Our standard rewinding materials have given excellent service over the years. We use Class H amide/imide wire (GP200), Class H epoxy varnish (Sterling U475PH), 95-5 tin/antimony solder and fiberglass banding. Slot cell insulation is rag/Mylar/rag paper. Nomex is available, on request, for an additional charge, but is normally not necessary. Stator top sticks are DMD and armature wedges are wood (maple). Armatures receive two dips and bakes at 375F. Stators and fields normally get one dip and are baked at 350F. We have found that our Class H varnish encapsulates the lower rated materials, giving a long useful life without the need for a full Class H system.
Armatures are static balanced using special brass wedges and/or EPO Dynaweight. Because of the inherent symmetry of the winding, this has proven satisfactory even for very high speed armatures such as routers and grinders. Large armatures should be dynamically balanced. Our customers normally take care of this after reinstalling fans, sheaves, etc.
All commutators are removed for slotting and testing (bar-to-bar at 30VAC and bar-to-ground at 1500VAC). All vertical and tang style comms, as well as most molded comms must be replaced. We maintain a large inventory of commutators and have developed a number of new sources in recent years. If necessary, we can usually adapt an existing comm even if the original is long obsolete. However, if a comm cannot be modified, there are manufacturers in the US and Europe that will make custom comms. The price is high, but for a motor that is irreplaceable it is an alternative. We strive to keep comm prices as reasonable as possible, but prices can change without notice depending on our suppliers’ whims.
If a comm must be ordered for an emergency job, we do all we can to expedite delivery. We now have several suppliers that can custom build new commutators very quickly, though the adders for this service tend to be quite high. However, if your customer has a production line shut down, the extra cost may be worthwhile.
If you are not sure if you have a bad field , please send it to us marked "Test First". We are happy to test fields FREE rather than put a good armature back into a bad field. Ohmmeter and 60 HZ ‘drop’ tests are not capable of detecting single turn shorts (which are death to an armature). Our 600 HZ equipment gives a good positive test. Wrap the field and armature separately to avoid damage to the windings in case they are OK.
The same is true for permanent magnet fields . PM fields are not necessarily permanent! High no-load speed, poor commutation, shifted neutral, low torque or high current at full load all indicate bad magnets. We have an electronic permanent magnet tester that gives a reliable indication if a PM field has been damaged (by a motor stall, for instance) and will be happy to test your field. These magnets are FRAGILE. To avoid cracking or chipping the magnets, do not ship them with an armature rattling around loose inside the field . Modern ceramic ferrite magnets do not need a keeper. There are now a number of sources for re-magnetizing service if it is needed. If you see many PM motors, consider building your own tester. This link will take you to a description of our PMT-2 permanent magnet tester. There are a number of articles on the Web on building Hall Effect gaussmeters that are even simpler than the tester we built. There are also reasonably priced commercial Hall Effect testers on the market.
On stators, number your leads and we will number the rewind accordingly, as well as provide a sketch of the connections. Remove and keep any parts that might be damaged in shipment, including capacitors and start switches. It is not necessary to remove fans or bearings from armatures. We will re-install fans and then check the balance after the bake. We will return bearings loose so you can replace them if necessary.
UPS will now ship up to 150 pounds. UPS Next Day Air and Federal Express both give reliable overnight service, though UPS usually gets here in the morning. Afternoon receipt may add an extra day to our turnaround. Express Mail is 1 to 2 days (or more) depending on the distance. In an extreme emergency, we can arrange pickup and delivery to the Portland Jetport, but it is 50 miles each way and charged accordingly. We have a good small airport nearby (Eastern Slopes in Fryeburg, Maine) which is handy if you want to fly something in yourself. Call ahead so we can meet you or pick up the package.
Pack carefully! When shipping multiple parts, wrap each one individually to prevent damage to shafts, fans or comms. Trap armature shafts with solid padding or else they will work their way right through the side of the box. We have found that tightly packed crushed newspaper is the best all around packing material. Assume that the box will be dropped, thrown, kicked, and generally abused in shipment . It is especially important to allow room for the box to ‘crush’ without damaging fans or stator shells. You should feel comfortable enough with your packing job that you wouldn’t mind dropping the box yourself! DO NOT USE STYROFOAM PELLETS! ‘Popcorn’ simply does not work with high density parts like armatures and stators. In most cases, you will just leave a trail from your shop to ours and the parts may well be damaged or lost.