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Old 2014.12.19, 04:43 PM   #1
ianc
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Join Date: Jun 2002
Location: Redwood City, CA
Posts: 562
MR03VE build with JesseT's side rail chassis

Hi folks,

Well, here's a project that I've just finished the initial assembly of. A very clever Finnish fellow named Jesse Tuominen came up with the idea of creating a side rail sub-chassis for the MR03 and making it available at Shapeways. Arch2b first posted about it (to my knowledge) here.

The design looks very promising because it gets rid of the wacky H plate that the factory rear suspension is based on and uses the idea of side rails like larger scale cars (and the MRCG) for more consistent steering behavior.

I decided to do an MR03VE build based on Jesse's chassis, but wanted to stick with the stock kingpin-style front end, which has always worked fairly well IMHO. Jesse's designs had been based around the PN A-arm front ends, but he kindly drew up a version based on the stock front end and made it available to me as a beta to play with.

First, a couple of words about the chassis itself. When you order from Shapeways, you have the option of ordering in white or black. Black is a bit more expensive, but looks cooler. Or so I thought... Actually, the black finish is not at all smooth, and the piece is really just the white printed material sprayed with some black grainy material which is not ideal for this type of project. After I cut it apart, I was soon scrubbing off all the parts with a toothbrush to knock off the dust and try to smooth it down a bit. Further scraping was required where parts joins were made to assure a good fit. This added considerably to the preparation time, and I would probably go with the part in white if I had to do it again.

Overall however, the parts themselves are pretty amazing it terms of fit. The kingpin balls (which I was a bit worried about) pop smoothly in with excellent movement, and are retained nicely under tension by screws. All parts have really excellent fit right out of the box for this kind of medium, and the design is clever and well thought out. I was very impressed. I did have a couple problems, but nothing terrible, and keep in mind that this particular version of the chassis was a beta, and Jesse continues to improve these parts.

Here's the way the chassis arrives from Shapeways:





Here are the constituent parts cut apart, cleaned up and laid out to show the overall design. It should be noted however that the triangular shock mount shown in the middle was not included in the chassis and needs to be ordered separately to complete the car. Maybe this necessary part could be included in the chassis parts in a future revision to avoid confusion and extra expense. Another point is the detachable side rails. Earlier versions of Jesse's chassis included the rails as integral parts of the chassis itself and they look considerably beefier. These look rather fragile to me, and I'm hoping that they're not an early casualty when I bring the car to the track. Another improvement to the chassis might be the inclusion of a spare set of side rails. The detachable rails do modularize the design in a desirable way, but take extra time to prepare to ensure a good fit. They can be seen in the picture above to the extreme left.



I began by installing the front end, and as mentioned, this went very smoothly, with a great fit for the kingpin balls. I went with Reflex's low profile parts, and was very happy with the resuling suspension action:



After finishing the front end, I moved on to sorting out the motor pod. I used a 3Racing diff with a PN 64P spur and pinion and had some troubles getting the motor turned enough with the circular cam end pieces to get a good mesh. As you can see here, I ended up needing to grind a bit off to get the motor rotating enough. These pieces might do with a bit of modification to allow more rotation of the motor in future revs. You can see the white printed material where the black coating has been ground off. Nothing a black sharpie won't fix.



This next (awful) pic shows the machine screw I used for the motor pod's gimbal pin. I just filed the end round and threaded it in from the the opposite side, figuring I could adjust its length later if required. Believe it or not, there is actually clearance for the motor with the length, although I should probably go 2 mm shorter. I used machine threads wherever possible in this project, and the chassis requires both cap head and countesunk screws in various lengths. Many of these I didn't have readily to hand, so I went to boltdepot.com, where they had everything necessary for very reasonable prices. Their shipping was extremely fast too.



Once the the motor pod was sorted out and mounted, I took care of the wiring and soldered directly to the board with PN's silicon wire. I've read that this wire was rather stiff and caused some tweak, but this particular batch was actually quite pliable and caused me no trouble:



Here are a couple more shots with the shocks mounted. I used PN's side shocks as well as their center shock:



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