Part 16 - Seat Pan

There's no off-the-shelf seat for the War Eagle frame so you get to make your own. To start making the seat pan, mask off the area of the seat using masking tape and then cover the taped off area with aluminum tape. The aluminum tape will prevent the resin from being absorbed into the masking tape and also present a smoother surface that makes removal of the molded seat pan easier. It also makes the job take twice as long. I have seen it done without the layer of aluminum tape but it would make a mess if you missed a spot with the masking tape and had resin leak through onto your motorcycle.

Use blocks of wood, foam or anything else you have handy to make clearance underneath the seat for things like the battery, electrical relays and such. The picture shows the spacers I used to create extra clearance for the battery, electrical control module, bolt heads for the fender and the fender gussets. The finished seat pan is going to sit a little higher off the frame than when you mold it due to the seat covering. Providing extra clearance for things like bolts and gussets is not strictly necessary but if you move your fender mounting points slightly to realign your fender in future, it is nice to know you have extra clearance under the seat to accommodate this. Now is a good time to make sure the rear wheel and fender are aligned properly! I allowed for at least 1/8 clearance above and to each side of the gussets and bolts.  Just make sure you don’t have undercuts since you will be pulling the completed pan upward to remove it from the bike. With undercuts you will need a grinder to cut your pan free and start all over again….

I extended the seatpan area to the rear of the fender so that I could make a detachable pillion pad for a passenger. I used a piece of Styrofoam to make the backrest (more like a butt rest actually). I used 3/8" vinyl tubing to provide a form for strengthening ribs between the horizontal and vertical pieces to reinforce the back rest.


A plastic drop cloth was draped over the motorcycle and a hole cut where the seat will go. The edges of the drop cloth were sealed with masking tape. You don’t want resin on the bike anywhere other than the seat pan.  The resin makes a real mess.

I marked the the outline of the seatpan with a permanent Sharpie. This line will magically transfer to the fiberglass when you lay on the wet layers of fiberglass and resin, permanently embedding the lines in the fiberglass which is a useful trick for when you need to trim the seatpan to size. I went about 3/8 down each of the side support rails so that the seatpan would have built in side to side stability. It doesn’t just sit on top of the side rails, it fits over them. You don’t want to go too far down. If you pass the midpoint of the curvature you may not be able to get your seatpan off.

Cover the seat pan area with a mold release agent. This will make it easier to remove the seatpan after it has cured. I used Leather Boot Conditioner…. Car wax will probably also work or you can buy special mold release products. If you don’t use mold release it is going to be tough to remove the seatpan.

Use a dust mask and appropriate gloves to protect your hands and lungs from the fiberglass.  I used double layer nitrile gloves and 3M 95 sanding mask.

Prepare the fiberglass. I used both fiberglass mat and fiberglass cloth. The cloth is stronger than the mat or so I’ve read. Why use both I’m not entirely sure but the result is very strong.

A large piece of cloth is roughly cut to the shape of the seat pan area with some overlap on all sides. Cut slits into the cloth in areas where it is difficult to conform to the contours by hand and cut smaller pieces to fill these in later. Do a rough trial fitting to see where your problem areas are. Then the mat is cut into 5” by 2” pieces (no need to measure….) and some is shredded by hand. The smaller pieces make it easier to work into the tighter curves and corners.

Make sure your work area is well ventilated. The resin creates a lot of fumes that may not be good for your health. Remember the dust mask for protection against airborne glass fibers. If you are making seats everyday you may want to invest in more sophisticated safety equipment. Mix the resin to the manufacturer’s specification and work fast. Too much hardening agent and the resin will set before you can use all of it. Too little and it will take days to cure or never really cure properly. For your first time out, I recommend using the manufacturer’s recommendation plus an extra drop or 3. People with fiberglass experience use up to double the amount of hardener and work fast since they know what they are doing. I don’t and therefore didn't. The chemical reaction gives off heat so adding more hardener increases the speed of the reaction which increases the heat output.

To start, paint a layer of resin onto the seatpan area (quickly) directly over the aluminum taped area and then lay on the first pre-cut large layer of cloth and position it as smoothly as possible. Working quickly, paint another layer of resin on top of the cloth and make sure the entire cloth is saturated. I found it useful to dab the paint brush up and down instead of making painting strokes to stop the cloth from moving around. Add another complete layer of the shredded/2x5 mat pieces and cover with resin. Keep adding layers of the mat until you have your desired number of layers of mat - at least 4 (total layering is 1 x cloth layer + 4 x mat layer). You may need to make more batches of resin if you work a little too slowly and the resin in the cup starts to gel. I mixed 6 ounces at a time and made at least 3 batches – lost count. Add 2 final layers of cloth to the top and cover with resin (1 cloth – 4 mat – 2 cloth). This arrangement ended up being very strong. Not sure why you cant just use the cloth for all layers but that is an experiment for next time.

How much resin to add? Just enough to saturate the cloth or mat. When the cloth/mat changes from white to yellow resin color, that’s enough. No harm done adding more but it will not make the seat any stronger.

Clean up and leave the seat pan to cure overnight. If it doesn’t cure properly overnight and is tacky to the touch the next day, mix up another batch of resin and add twice the recommended amount of hardener. Working fast, paint a thin layer over the seat. This will set up hard and help cure the tacky layer underneath at the same time. Leave the seat to cure another night. A heatgun or hairdryer will accelerate the curing process but be careful not to accidently burn the seatpan doing this.

The resin in the mixing bowl gets pretty warm when it starts going from syrup, to gel to solid.

When the pan is dry, pull upward to release from the motorcycle. Depending on how well your mold release agent worked, your pan will come up without a fight or stay stuck to the masking or aluminum tape. Use industrial leather gloves to grip the seat as the edges can be very sharp and the fiberglass will cut you.

Using adequate dust and eye protection, use a cut-off wheel or other appropriate tool to trim the seat pan to shape. If you don’t have a dust extraction system, do this outside or your garage will be covered in white powder that takes forever to clean up and gets in everywhere.… Don’t ask me how I know this….

A dry fit to make final adjustments before prep for upholstering the seat.

Sand the edges smooth. Mark a line all the way around the seat about 1.25 inches in from the edge. Make sure this line clears your frame or you will have rivets grinding the hell out of your expensive paint.

Mark points about an inch apart all the way round.
Drill holes through the marks with a 3/16 drill bit or whatever size is needed based on your rivet diameter.

Cover the edges with Edge Banding. I got mine from AutoZone. The edge banding will prevent the fiberglass seat edge from cutting through the leather.

We are now ready for phase 2 – padding, shaping and covering the seat

While researching the method for building the fiberglass seat pan, I found a number of useful sites that I used as a basis for making my own:



http://www.454rider.com/ebook/scr/How%20To%20Make%20A%20Fiberglass%20Seat%20Pan%20.htm
http://stargis.net/webslinger/Docs/Howtomakeafiberglassseatpan.pdf
http://www.customfighters.com/forums/showthread.php?t=22549

Part 15 - Rear Fender and Tail Light

Once the rear wheel was centered and adjusted to the correct drive belt tension, the fender could be mounted. The fender is 13.5" wide suitable for a 300mm rear tire. The fender is made by Kustomwerks and supplied with 2 internal struts. The struts are 1/4" thick and 1" wide. The fender is "chain cut" for a right side drive. Due to the large differences between custom frames, you have to fabricate your own mounting.

Kustomwerks Fender Detail

The hidden shocks have roughly 2.5" of travel so a styrofoam spacer was made to hold the fender in place about 2.75" off the rear tire. More styrofoam was placed under the rear edge of the fender to keep the rear edge 1.25" off the tire - the tire moves roughly tangential to this edge so this clearance is mainly to allow for small rocks and other road debris to move through and to allow belt tension adjustments in future. The shocks are currently adjusted so that the bike is lower than it would normally be for riding. This will eventually result in a little more than 1/2" of clearance between the tire and the underside of the fender when the rear wheel upward travel limit is reached. At this time, there are no bumpers to stop the swingarm - these will be added at some point in the future.

Fender Spacer (click to enlarge)

A poster board template was cut out and made to fit the curvature of the fender. A carpenters profile gauge was used to simplify the process. I tried to use the edge of the fender to create the profile but the profile at the edge didn't match the profile further up the fender.

Poster board template for fender mounting plate (click to enlarge) 

The cardboard template was re-traced and an extra 3/8" added on the insides of the arms to connect with the hidden internal struts. The template was sent of to a local welder who cut the pattern out of 3/8" steel. 

Fender mounting plate rough cut (click to enlarge) 

Slots were cut into the fender to allow the arms to connect with the internal struts. The first paper template (without the 3/8" thicker arms) was used to determine the bottom edge of the slot and a parallel line 3/8" higher up determined the top edge. An angle grinder with a 0.080 cut-off wheel made quick work of creating the slots.

Slotted for mounting plate (click to enlarge)

The mounting plate was repeatedly adjusted by grinding away high spots until it matched the profile of the fender as closely as possible. Eventually, the fit was reasonably snug.

Grinding the mounting plate to fit (click to enlarge)

Mounting plate adjustment complete

The steel was badly pitted and had some scale. Both scale and pits were removed by grinding the surfaces on both sides. 

Grinding the surfaces clean

The fender and bracket were returned to the bike and tacked into place. This was done on the bike to make sure that the fender was centered and in the correct vertical orientation with respect to the tire. (Note the aluminum flashing to protect the bike from welding spatter.)

Fender tacked in place

The fender was removed from the motorcycle and the struts tacked into place on the inside of the fender. The ends of the struts were tacked to the mounting plate arms that protrude through the slots toward the inside of the fender. 

Internal struts positioned for tack welding to the mounting plate and to the fender (click to enlarge)

Tacking the internal struts in place

Checking to see if everything is centered and square

Once everything checked out okay, the mounting holes in the frame were transferred to the mounting plate using the poster board template and the holes were drilled.

Mounting Holes (click to enlarge)

Finally, the fender was mounted to the frame using 3/8-16 1.5" grade 8 bolts with grade 8 Nylock nuts and washers.
The fender is very sturdy but I doubt whether it will hold a passenger without additional reinforcement. The mounting frame arms flex somewhat with moderate downward pressure on the peak of the fender. This was confirmed with a Solidworks FEA model.

Fender bolted in place

Made some gussets to add extra support to the fender.

Cutting the gussets out of 1/4" cold rolled steel

Fender Gussets

Gussets test fit

After the test fit, used the flux core welder to weld everything in place. The result was ugly. I redid the welds with a TIG welder and got a reasonably good looking result. The TIG has a big heat affected zone compared to the flux core welder and things get very hot.

Gussets TIG Welded

The internal struts were finally welded in place. I couldn't run a weld bead down the complete length of the strut because access is difficult so I welded a number of heavy duty tacks instead.

I wanted to integrate the license plate holder into the rear fender without cutting into the fender. I think it is important to have the tail light in a highly visible area. Mounting tail light off the rear axle looks cool but is bad for visibility. I fabricated a sheet metal part to hold the license plate. The sheet metal was bent by hand and dead blow hammer using the rear tire as an anvil.

LED License plate holder

Ugly

The result doesn't look to bad from the rear but from the side it looks pretty damn ugly and was therefore eliminated as an option. Removed the LED tail light from the license plate assembly and  fabricated a sheet metal part to hold the LED assembly to the rear fender.

Some months later, this is what the fender looked like after body molding and primer

The LED taillight only draws 110mA when the brakes are applied which allows the use of 24 gauge wire. This makes it much easier to route wire through a 3/8 brake line that I welded to the underside of the fender to protect the wiring from rocks and other road debris.

Part 14 - Rear Wheel Centering

Before the rear wheel was aligned, the rear swing arm was removed to install the belt. The drive belt is a Panther 1-1/2"  139 tooth purchased from Demons Cycle eBay store for $139 or $1 per tooth.

Panther 1-1/2" 139 Tooth Drive Belt

Swingarm removed to install the drive belt (click to enlarge)

The length of the belt was calculated using an online calculator from www.scootersperformance.com. You need to know the number of teeth on the front and rear pulleys, as well as the center to center distance between pulleys. Make the measurement with the rear wheel roughly in the middle of it's forward/back adjustment position to allow for future adjustment and changes between the ideal belt length and available stock belt length. The transmission pulley has 32 teeth, the rear drive pulley has 65 and the distance between centers is approximately 630mm.

The calculator determined the required belt length to be 138.5 teeth. Rounded to 139 which is fortunately a typical stock length. You may need to play around with your forward/back wheel placement to get a measurement that is close to an easily available stock belt length.

Once the rear swingarm and the drive belt was in place, a laser level was used to align and center the rear wheel with respect to the pro-street frame backbone.

Rear wheel and belt installed

To find the center of the rear wheel, a strip of blue painters tape was placed crosswise over the tire and a mark was made where the tape crossed the tire case edge on each side. The tape was lifted and placed on a flat surface (kitchen counter...) and the distance between the two endpoints was measured and the midpoint between the endpoints was marked. A second piece of tape was run next to the first on the kitchen counter and the marks transferred to it. Then both pieces of tape were returned to the rear wheel roughly 5 inches apart. 2 strips of tape were run lengthwise down the tire one on each side of the center marks to highlight the center of the tire.

Marking the tire center line

Don't use the mold parting line on the tire as the center reference for the tire. For some reason, tire molds aren't balanced around the center of the tire, so the mold parting line (small ridge of excess rubber you see on a new tire - called "flash") is off center by at least 1/4"

Rough alignment of the rear wheel using a laser (click to enlarge)

The laser was sighted down the backbone and the rear wheel was moved into position by sliding it left and right on the axle until the laser indicated the approximate center of the tire. The rear wheel axle adjusters where turned to straighten the rear wheel so that the center line of the tire marked by the tape was in alignment with the laser and thus the backbone. The 7/16 wrench used to manipulate the axle adjusters had to be ground down to fit in the opening. Here's a picture of the customized rear axle adjustment wrench.

Rear wheel axle adjusters Adjustment Wrench

With the rear wheel centered, the lengths for the spacers were measured using telescoping gauges, a digital caliper and a bit of guestimation for where the telescoping gauge wouldn't fit properly. This resulted in the following lengths:

Left Spacer:    2.145"

Right Spacer:  2.130"

Right Spacer between Pulley Brake Bracket and Swingarm:  0.325"

A 1-1/2" OD, 1" ID by 1 foot long stock 6061 aluminum pipe was ordered from McMaster.com for roughly $16. The ID of the tube was on the small side of the tolerance (0.990) so had to be bored out to fit over the 1" rear axle. The spacers were roughly cut to size using a hacksaw and then machined to final dimensions on a  lathe. Machined 2 handlebar spacers to fill in the gap between the handcontrols and handgrips while I had access to the lathe. 

Machining a rear wheel spacer

After the spacers where turned, they had to be sanded smooth and eventually polished. This was a time consuming process but considering the financials of 5 spacers for $16, worthwhile. The final polished spacers ended up as shown in the image below. The remainder of the stock tube is on the left, followed by the 2 handlebar spacers and 2 rear wheel spacers turned on the lathe, a purchased spacer for comparison and finally the small spacer between the pulley brake bracket and the swingarm also turned on the lathe):

Rear wheel and handlebar spacers

Left spacer installed

Right spacers installed (click to enlarge)

The tension on the belt is determined such that a 10lb upward force on the lower belt at approximately the midpoint between the pulleys results in a deflection of about 3/8". A caliper can be used to check the distance from the rear of the axle mounting to the axle to make sure the wheel is correctly aligned with the frame. The measurement should be the the same for left and right right.

Checking wheel alignment - repeat on right side

The axle bolts need to be torqued to 50 ft.lbs for final assembly. Here's a site with useful information regarding belt tension adjustment and belt care in general
http://www.nightrider.com/biketech/hdbeltdrive.htm

A belt tension gauge for applying the required 10 lbs upward force is available on ebay for around $30.

Belt Tension Gauge

Visit eBay store ridersdiscount and search for MOTION PRO BELT TENSION GAUGE 10LB