Antique & Classic Automobile Restoration Tips
The Incredible Threaded Rivet
A simple fastener that has the appearance of a rivet, a domed head with no visual signs of using a tool to tighten its grip. Down its shank, it has standard US threads to accept common nuts to that can be used to fasten hardware just as a regular screw might be used. While the threaded rivet is not necessarily new, the use for trunk restoration maybe one application that had not been considered. Threaded rivets are available in a variety of screw sizes of 4-40, 6-32, 8-32, 10-32 and ¼-20 and most sizes have head shapes of either round or truss head. Length’s vary from 3/8 inch for the smaller 4-40 to one inch long for the ¼-20 size. They are available in stainless steel for all sizes and in brass for just the 8-32X1 round head only. Prices range from .20 to .90 cents each depending on size and head style. A significant advantage of using the stainless steel version is that they can be polished to provide a long lasting chrome like appearance. Two suppliers of threaded rivets are Restoration Supply Company, Escondido, CA and Big Flats Rivet, Big Flats, NY. The application for threaded rivets on trunks is to fasten hardware components onto the trunk itself. Examples are the trunk handle loops, strap hinges, piano hinges, handles or pulls, latches & clasps, and decorative metal or leather straps. These are the pieces that would be fastened after the exterior of the trunk has been covered, but before the inside lining has been installed.
The technique presented here is using the threaded rivet with either brass threaded wood inserts or Tee nuts, available from the local hobby shop, directly from Du-Bro Products, or the industrial supplier McMaster-Carr. The Du-Bro wood inserts are small and may suit the thin wood found on trunks better than other versions. Model airplane and boat builders use these small brass inserts wherever there is an application to repeatedly fasten and remove pieces. To aid in tightening the threaded rivet, a Dremel tool and thin cut off wheel is used to cut a slot across the tip of the threads where a small slotted screwdriver can be used from the back side. Small nuts and washers could also be used, but the benefit of using inserts and Tee nuts is to conceal them into the wood. Drilling and inserting the numerous brass inserts can seem time consuming, especially when a piano hinge is involved, but the finished results are outstanding. The holding strength of the threaded rivet is superior to that of nails, especially if the wood has been weakened from previous nail holes. The brass wood inserts are set by drilling the appropriate size hole in the wood and using a regular machine screw to drive them slightly below the surface. Each one should be trial fitted with a threaded rivet to ensure no burrs developed while setting the brass insert. Also, the use of Kwik-Poly may be considered to improve the strength of weakened wood panels. As mentioned earlier, the inserts are set prior to covering the exterior of the trunk. After the covering has been glued on, each of the holes can be located and a small hole cut using an Exacto knife. Each threaded rivet is set by first screwing it by hand and finish tightening it using a small slotted screwdriver from the inside (i.e. unscrewing it). The inside material (cloth or paper) will eventually conceal these small holes.
Electrical Connections, The Importance of Soldering
So much depends on the electrical system that during restoration or maintenance, extra care should be given to not only the wiring, but more importantly their connections. This restoration tip examines good connection techniques and the importance of soldering.
Electric currents run through the vehicle’s wiring from many different components. There are sources such as the battery or generator and there are loads, the components that require the current to operate. Ignition coils and breaker points, headlights and taillights, horns, and fans are all examples of electrical loads. All of these have one thing in common, they use wire between them and all use some sort of connector to transition the wire to a fastener. The most common connector is a wire terminal or lug. They can be open such as a spade or hook type and closed forms are called ring terminals. Electrical connections to these terminals have two properties associated with them; mechanical and electrical. A mechanical connection is a friction mating of the terminal metal to the wire itself, crimping or crushing the metal around the wire. All terminal types make this mechanical connection to the copper wire and in some cases include the wire’s insulation for greater strength. The mechanical connection is intended to provide an electrical connection while also providing strength if the wire is pulled or strained. Electrical connections are those that use solder around the wire to improve the electric current flow and should not be confused with a mechanical connection. While strong most times, a solder connection is not a substitute for a good mechanical connection. The best electrical connections include both mechanical crimping of the terminal around the wire followed by soldering.
Wire is rated in sizes called Average Wire Gauge (AWG) which is essentially the wire’s diameter, expressed in either inches or millimeters. A 10 AWG gauge wire is approximately 1/8 inch in diameter and 36 AWG gauge, one of the smallest gauge wires, is a mere 0.005 inches or about the size of a human hair. The higher the AWG number, the smaller the wire. Wire gauges can be a single piece of wire called solid core or made up of multiple strands of smaller gauge wires called stranded core. The benefit of stranded gauge wire is that it is more flexible than solid core. Stranded wire can be made up of a few medium size wires, a couple dozen smaller size wires or in certain cases over one hundred very small (human hair) size wires. Stranded wire examples of a 14 gauge wire include 7/22 (seven 22 gauge wires) and 19/27 (nineteen 27 gauge wires). Overall, the total diameter of the wire doesn’t change, just its composition. Stranded wires are tightly twisted together while the insulation is applied during manufacture. The significance of a wire’s gauge is the amount of current it can safely pass through it while the number of strands indicates its flexibility. Table 1-1 shows this for some common size wires.
|AWG||Strands||Strands||Diameter (inches)||Maximum Ampere Rating|
The flow of current through the wire to the terminal occurs predominantly at the outmost strands of wire where they make contact with the terminal’s metal collar. The contact of single strands, their round edges against the terminal’s collar don’t provide much surface area to carry the current. When crimped, the wires flatten out to conform with the collar, but the outer strands are still the connection point for current flow. Even if the crimp is perfect and all strands are making contact, there is a looming problem that began the minute the wire’s insulation was stripped: oxidation. Oxidation occurs on wire strands that are exposed to air which is shown for the 7/20 wire illustration. It deteriorates the wire much like rust does to exposed sheet metal. It begins on the wire’s surface which actually passes a small amount of current through it. The current heats the oxidized area which in turn accelerates and creates more oxidation. This oxy-heat cycle continues to the point where the wire’s contact to the terminal is reduced and current ceases to flow (through the affected strand). This puts more current through the other remaining strands accelerating their corrosion. The result is a corroded terminal that prevents current flow and depending on the wire size and amount of current, can become so hot to initiate a fire. Using a stranded wire with more strands like the 19/25 shown above provides more strands to make contact and less air for oxidation. However, the same process will occur, it just may take longer to fully corrode. The simple way to 1) improve the contact surface area of the strands to the terminal and 2) prevent oxidation from forming (by blocking air from getting to the strands) is to add solder to the connection. Solder will fill in all around each strand as well as the entire surface area of the terminal’s collar. The result is a way for the current to flow through all the strands of the wire and pass through the terminal evenly without any loss. The noticeable improvement will be brighter head lights, tail lights, and brake lights. Even the horn will sound louder and the heater fan will spin faster. What is equally important is that by taking the time to evenly crimp and solder a wire’s terminal, it will provide years of corrosion-free service. The final part of a good electrical connection is insulating the terminal’s collar. The yellow or blue plastic shield found on terminals may become loose after crimping and almost certainly slides off when heated during the soldering process. The simple answer is to just remove the plastic shield altogether and use a special insulator that will conform to the terminal. Shrink tubing is a vinyl hollow sheath that when heated, reduces its diameter to half of its original size. Two variations are available, thin wall and a thick wall. Both meet the electrical insulating needs, but the thick wall version “just looks better” for auto restoration. Actually using two or even three layers of thick wall shrink tubing over one terminal provides the cosmetic appearance of a rubber insulator originally used in the 1920’s – 1940’s.
Kwik Poly is a Polyol product using two agents, a base and a catalyst. It is packaged in two separate metal containers, each having the viscosity (consistency) like water. Equal amounts of Part A and Part B are mixed together to create a thermo-chemical reaction for it to cure. Set times are generally around 5 minutes, can be handled in about an hour and full cure is within 24 hours. The low viscosity of Kwik Poly makes it ideal for wood as it absorbs well into the wood fibers and makes a strong bond, not just on the surface, but deep into the wood material. It adheres to wood or to itself which allows for it to be applied in layers, an especially important benefit when building up a particular area. It even can be mixed with various dry fillers such as silica powder (included in the kit) or your own fillers such as saw dust, aluminum powder, or steel shot/granules. Adding filler increases the mixture volume and improves its cured strength. The amount of filler added depends on the application, a little to provide some extra body to the joint or cavity to a hefty amount where the mix has the consistency of a paste. Under no circumstance can a liquid be introduced to the Polyol while it is curing. Cured Kwik Poly Polyol can be sanded, shaped and even polished using rotary tools such as a Dremel. It has a mixing ratio of 1:1, equal parts of the base (Part A) and the Catalyst (Part B). Thick or thin, Kwik Poly can be used as a combination filler, coating and a bonding agent.
Kwik Poly can also be mixed with colored dry powders to color the bonded area using the many available colors found in the Powder Coat trade. One color can be added to a single mixture of Polyol or two different mixes of Polyol having two different colors can be prepared. The intent of the multi-color multi-mix is to inlay a different color mix just as its curing. Swirling the darker color into the lighter color just as the Polyol is setting recreates colored lines in plastic type repairs (such as steering wheels). Start with dispensing the required amount of Part A and add the desired silica filler (if needed) and powder color and mix thoroughly. When ready, dispense the appropriate amount of Part B into the mix and again mix thoroughly. If doing a two part repair, time the points when mixing Part B into each mix at 60-90 seconds so that the base color cures slightly ahead of the accent color Polyol. When the base is nearing set-up, simply swirl in the accent color (white and black sample).
The basic approach to working with Kwik Poly is 1) plan ahead by having all pieces clamped or fitted, and 2) mix only the amount that is needed for the immediate task. The use of the drinking straw works well to minimize wasted material by providing small amounts into a paper cup while maintaining the critical equal amounts of each part. Using dedicated straws for each part, immerse the straw fully to the bottom of the container and using the index finger over the straw method, draw out and dispense the required amount of each part. A tip is to mark the top of each straw with a magic (Sharpie) marker; red for Part A and black or blue for part B. This will ensure you don’t mistakenly use the wrong straw with the wrong Part and possibly contaminate the entire can. If the job looks like it will require more than usual, dispense several straw-fulls, just maintain equal amounts of each. As the amount in each can is used, the amount in each straw-full will become less and less, so just account for that when estimating the job. Other important tips are the mandatory use of disposable gloves (material will wick through the paper cup to the fingers) and use of coffee stirrers for mixing. Thin wooden stirrers or tongue depressors in whole or sliced lengthwise seem to work well for mixing and “dabbing” the Polyol into the repair area. A note about working with wood. Wood can absorb moisture and Kwik Poly Polyol does not react well with water and for this reason, the distributor recommends using plastic utensils for mixing. Wooden stirrers can be used, just ensure they’re dry and stored in a air tight container. Another tip is to load a mixture of Polyol into a small 1-3 ounce syringe and inject the mixture into hard to reach areas. Care must be taken to dispense the Polyol and remove the unused portion and rinse with cleaner before the polyol sets i.e. within 4-5 minutes. Order what is needed for a particular job knowing that Kwik Poly has a advertised shelf life of 24 months (actual experienced 12-18) when stored in a cool dry place. Prices for a pint kit are $15 plus shipping, quart and half gallon kits are also available and an abundance of other information is available on the Kwik Poly website. Kwik Poly can be shipped via UPS. It is recommended that you experiment with Kwik Poly on small pieces around the shop to get a feel for its properties such as penetration into wood and other materials, amount and types of fillers, and curing times.
Car bodies that have a wooden frame usually are built on substantial structural pieces on the left and right sides called frame rails or sills. Depending on the car manufacturer, the body rests on special fibrous shims that are wedged between the underside of the body and the chassis metal frame. The number of locations along the body frame rail where shims are inserted can vary but five to seven of them per side are common. By adding or removing the number of shims at each location will effect the alignment of the body to the hood and more importantly, the alignment & spacing of the doors. On a sedan for example, adding shims under the front door post “pushes the door” upwards in the event of a sagging door. A common problem though is the wood rotting out at the point where the shim is located. There are probably several reasons why this occurred by the most plausible is the fibrous shims retaining moisture. The result is the shim stack collapsing into the cavity created by the rotted wood and the body or at least a certain section of it is resting on the chassis frame (Figure 1). Since shims play such an important role in overall body alignment, the wooden area must be repaired, hopefully with as little affect to the remainder of the body frame rail/sill.
The repair suggested here uses Kwik Poly as a filler with a bit of special preparation to the area. The body bolt and nut assembly are removed and the body is lifted slightly to permit the placement of small blocks of wood in front and in back of the area to be repaired. These small blocks temporarily carry the weight of the body while keeping it relatively aligned. Next a thin piece of 1/8 inch Luan plywood wrapped with several layers of wax paper is placed and wedged to the underside of the area to be repaired. The wax paper prevents the Kwik Poly Polyol from adhering to the 1/8 inch Luan which will be removed after the Polyol has cured. Depending on the cavity to be filled, small amounts of cotton can be wedged at the very front and rear of the cavity where the Luan meets the underside of the body to act as a seal for the Polyol (Figure 2). The intent here is to pour the Polyol into the existing body bolt hole and fill the cavity from above. Any area where the Polyol can seep out needs to be addressed and every repair is slightly different. The cotton trick seems to work well. While pouring the Polyol into the hole, make sure it is “topped off” at the top of the hole so it maintains full downward pressure into the cavity thus ensuring the cavity gets completely filled. The hole can be drilled out after the Kwik Poly Polyol has cured (Figures 3 & 4). Estimate the amount of Polyol required to fill the cavity plus a bit more. This is no time to skimp where the little bit left over is “pennies” given the ability and relative ease to address such a difficult repair problem. The mixture of Polyol should be as low viscous as possible (pour able) so care should be taken on the amount of silica filler added. One suggested preparation is to lightly coat the inside area of the cavity with a coating of Polyol (containing no filler) using disposable flux brushes. This coating will promote adhesion for the filler. Also Duct Tape can be used if the repair has a vertical area to be repaired. The Duct Tape can act as a temporary trough (dam) while the Polyol is poured.
This discarded bakers cooling rack makes a great way of storing and organizing the parts or materials for your restoration project. The drawers were made from particle board, but thin cabinet plywood would also work. All 30 of the small drawers are the same size, so cut all material at once and make an assembly line. The three larger drawers on top handle larger parts. The final touch (after painting just the fronts and screwing on simple handles) is to use self adhesive clear vinyl ID tag holders from your local Staples or Office Depot store. The card inside the tag holder can be removed or updated as the content of each drawer may change as the restoration progresses.
Save your old hotel room keys and use them as speaders for your final polyester filler. The thickness of these hotel room keys has just right amount of bending when applying finishing fillers. Also, scrap pieces of Formica make good mixing boards and can be easily cleaned using a single edge razor blade.
Scoops from coffee cans, Kool Aid, Tang or your favorite dry powder drink mix makes for a good means to scoop paint from a can when you only need just a little bit of paint. Instead of pouring over the can's lip, scoop out what you need. Next time you have to mix some epoxy for something, glue tongue depressers or other suitable extension to the scoop handle. Credit: Fred Johnson, formally of Oceanport, NJ.