Articulating Sidecar Project
Page 2
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Basics: An articulating rig pivots from 2 points which attaches the rig to the bike. I chose to use Heim joints instead of ball and socket mounts (which really are the same thing). Jay at Dauntlessmotors( suggested using 5/8" heim joints and noted that that would be overkill, however being the type to overbuild things, I went with way overkill and chose 3/4" heim joints from an offroad Jeep supplier. I was also able to buy the threaded tubing ends that the 3/4-16 grade8 bolts would secure the Heim joint ends to the bike engine frame.

Now here is where the Voodoo Mambo Jambo comes in. After reviewing many reference pics it was apparent that the front attachment point to the bike frame was usually higher (away from the road surface) than the rear mount. A few designs also had the rear mount closer to the sidecar (offcenter with the engine) while the front mount remained centered about the engine.

The first observation made sense! If the front mount is higher and the bike leans left then the front mount moves further to the left while the rear mount stays where it was. The effect of this, would pull the front of the car left and actually steer the car in the direction the bike is leaning. The opposite happens when you lean the bike right, the front mount pushes the front of the car to the right and assists the rig's turning with the bike.

The second observation made no sense to me, a Dutch guy said it helped the car to steer but I cant see that. Perhaps somone out there can drop me a note and explain the function of a rear mount being offset towards the car while the front remains centered about the engine center.

OK, so I'm sold on the higher front mount but noone could give me a formula to calculate the hieght offset? So what if I get it wrong and have to make the engine frame all over? Not an option..too expensive and I had a deadline to mfr and build this thing in 2 months so I could ride with my wife and little guy in the PA mountains on the 4th of July!

I ended up taking measurements from a Dutch guy I had been talking to who had just built a few leaners. I also made the front plate of the engine frame removable such that a different plate with a different offset could be bolted in place easily. So the question came from my Dutch bud: " If I change the offset, how will I be able to adjust the car frame to adapt to it"?..Answer: You dont have to, basically the front mounting outrigger of the car would move up or down an inch or so to meet the new height. Sure the distance in the X direction my vary a hundred thousanths, so I used a spacer in the stock trim that goes between the Hiem and the engine frame threaded insert. If I need to change the space to something thinner, thats easy. The car can ride an inch higher or lower in the front and noone will notice.

Engine Frame:

I needed to fabricate a strong frame that would mount to existing features on the later generation Boxer engine. I chose Stainless Steel though regular steel would have worked fine. I did all my final design in a program called Solid Works, which is a 3D modeling program (see It basically lets you build your part in 3D before you cut metal then generates the files needed by the shop to actually cut and fab the part. I di however need to convert the dimensions from my engine to data I could model. I started with thick paper and marked the holes on eachside by pressing the paper into the holes such that the hole imprint was left on the paper. I then used a straight edge and calipers to get exact, 3place accurate measurements of the holes I wanted to utilize for mounting the engine frame.

Based on the paper templates, I created parts in Solid Works (SW), and then cut them out of type 1 PVC (which is cheap and easy and quick to cut.) source:
I then was able to check the 3D model by assembling the PVC frame and mounting it to the bike. Once final adjustments were done and I was satisfied with the preliminary fit, I sent the prints to a waterjet cutter and had the stainless cut per prints.

I took the waterjet cut parts and using the mounting features/holes on the engine , I assembled the sideplates to the engine and held the bottom plate in place with a floor jack. I then tack welded a few beads around each part to hold the parts in working position. Once tacked, I took the frame to a buddy who builds custom bikes and let him do the TIG welding to finalize the frame.


Car Frame:

The California, Freindship One sidecar I purchased came with a torsion type suspension which rotated a swingarm against rubber elastomers in a square shaft centered on the rotational axis of the swingarm. I chose to build an entirely diferent frame than the car came with and also to put a more adjustable suspension under it. The car body I purchased is of fiberglass construction and unfortunately has the wheel well preset such that when the car is level and the wheel has about 3-4" travel, then the car rides fairly tall beside the motorcycle. The reason this is a problem is that if the car is riding tall, then the bikes available lean angle is limited unless I move the car further away from the bike. I started with the side of the car about 22 inches from bike centerline, which place the car wheel about 50 inches from the bikes rear wheel. I test rode the preliminary frame at these dimensions and it was a BEAR to handle..I quickly cut about 6 inches off the outriggers which helped exponentially on the handling.

Suspension: I built the suspension components such that every aspect of it can be dissassembled and modified if required. Self aligning bearing blocks suport the main suspension axle with clamping colars securing the shock leverage arm to the axle. A Honda CR80 shock exorber was purchased for dampening. The shock can be fully adjusted for preload, compression and rebound as well as interchangable spring rates and Nitrogen charge. Parts are readilly available for this off the shelf component. The leverage arm of the suspension has multiple mounting holes for the end of the shock such that the leverage applied to the shock can be adjusted.

Materials: I originally wanted to fab the tube car frame from aluminum, It would weigh about 1/3 the weight of a steel frame and could be as strong if the right grade was chosen. After speaking to chopper builders who use aluminum and racecar frame builders, I decided with steel. I couldnt get a consistant answer from the so called "experts" about the grade of aluminum needed. And then there was questions about anealing it or cooking it in an oven to remove all stress from bending and welding. I found powdercoaters with ovens big enough and willing to do it for me but there just seemed to be too much voodoo and not enough clear written rules for me. I chose 1018 steel tubing with .120 thick walls in 1&1/8" dia for the maincar frame. The outriggers were 1&1/4" OD and .120"wall thickness. I didnt do any finite element analysis(FEA) yet on the design but there is absolutely zero flexing of any members while riding any terrain. My design program has FEA capability with COSMOS, but I havent had the time to learn the ins & outs of that yet.


Bending metal: Gary at Chester County Customs bent all the steel tubing and TIG'd it. I took the basic frame, mounted the suspension components and wheel to it, then bolted the outriggers to the engine frame as it was attached to the bike and then spot welded the outriggers to the car frame. The spot welded frame was then taken back to CCC to do the final TIG welding to the frame and add the crossbar strut between the outriggers.


Final Fitup:
Once the main frame and outriggers were fabricated, I took all the pieces to my garage and with the engine frame bolted on the bike, I positioned everything in it's exact position so I could tack weld the outriggers to the frame in thier exact locations. This was a critical step as the alignment and height of the sidecar depended on the exact placement of these components. Many white chalk lines laid out on my garage floor and checked with squares and tapemeasures preceded the tack welds.


Steel plugs were weleded into the ends of the riggers, they were both tapped to 3/4-16threads so the heim joint threaded end could be screwed into them. The steel plugs were welded inplace at the ends of each tube and a side hole drilled into the outrigger and filled with weld front the plug upto the outrigger outer wall for added strength. I have 2 full inches of heim adjustment on each outrigger to lengthen or shorten its length to set toe/in toe/out

Once the frame was welded, I positioned the car body on it to lay out the body to frame mounting rails. I welded 3 cross bars made from 3/16 steel. Once in place the body mounting holes were transfered and then drilled and tapped.

Note the Cat on the bike is replaced with a SS home-made tube going to a 916 Can

I had to buy a windscreen since the original was lost from the owner moving the car from garage to garage during divorces. Jay at Dauntless motors again was helpful and directed me to windscreens. They had 2 versions of screens instock both of plexiglass, one tall & one short. I bought the tall one and it fit perfectly. I had to transfer the bodies mounting holes to it and drill the holes to mount it. A special bit is needed to drill plexiglass(The outer edges of the leading cutting edge are ground back so it wont hang on the plastic and crack it)and they sold it to me also.

Page 3-Improvements

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