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The Raven


I ran some wire rope for the steering today after letting the system sit for many months. Instead of the past method of four individual segments (two per bellcrank), I opted for two total. Each segment connects one axle. The wire rope is threaded from one clamp on the bellcrank and then through the steering block and back to the same axle. Because of this routing, the carrier no longer has the tension of two cinches per axle. The wire rope travels through the carrier and is cinched twice. I believe because of eliminating two ends being cinched the reliability will increase. We shall see.


During the last several days I began to notice the chassis was not sitting level at all. There was a difference of almost 3/8" when the height of the frame rails was measured from the floor. I also noticed the angles of the cantilevers were not the same. A simple shim between the shock end and thread adapter seemed to do the trick. At that point I began to see the major change I had caused by extending the wheelbase by two inches. That extension was necessary to fit the larger drive shafts. I spent so much time trying to level the frame rails that I finally noticed how much lower the entire chassis was sitting as compared to years passed. Also (and as I mentioned above), the suspension geometry became goofed up. The four cantilever links were no longer nearly vertical, and the relationship between them and the cantilevers seemed to be softening the springs. On top of this, when one axle is raised to its limit, the drive shaft rubs on the lower link. Sometimes I get these wild hairs to make some sort of dramatic change and when I see the results I realize that the change caused all manner of mechanical mayhem.

All of this became disconcerting so I decided to take the old link extensions that were originally made for the long suspension links and use them to lengthen the cantilever links by an inch each. This worked wonders and now the chassis sits a full inch higher off the floor. Plus, the cantilever links are supporting the suspension much better than before the change. I had no idea simply raising the chassis straight up would have such a great effect on the dynamics of the vehicle's suspension. Of course, by the time the PC board is in place with all of its components, the full height of this vehicle will be upwards of fifteen inches. Yikes. In addition, if I move forward with spacing the frame rails further apart, this may assist with the suspension geometry as well.


Back on page 26 I mentioned the slipper assembly and associated mechanics. Since that entry I have received another order from McMaster and now have the necessary hardware to fully design both front and rear slipper mounts. These two machined parts represent the last of the mechanical chassis work and a final end to more than twelve years of design and fabrication.

The front mount will hold the slipper shaft and the rear mount will hold the slipper shaft as well as the motor and its pinion.


In order to accomplish a slipper assembly that will mesh with the center differential, I needed to modify a Traxxas clutch pressure plate to hold the mating spur gear. This will yield a 1:1 ratio from top to bottom. The motor's pinion is a different pitch which means the mating primary spur needed to match. These are brass gears of the 32p variety. The larger spurs are 20p. The images show an Ofna 20p pinion which was to be the drive gear. I learned that would not work because one of them had to be drilled out to fit the motor shaft and with the equipment I have there was no way to ensure concentricity. Any wobble whatsoever means the gears will wear quickly. So, brass gears save the day as they match the shaft diameters perfectly.

Another issue was to keep any axial play to a minimum. For this I opted for a few nylon spacers and washers which will keep all of the clutch parts from moving along the shaft while spinning as well as maintaining enough space so as to avoid binding near the end bearings. So far, so good.

Once I have the mounts designed and double checked, I will order the parts to be made and update further.

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Content Updated: Sunday, September 04, 2016 at 10:25 pdt

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