Here is when you use math...

[krista]

This would be part 2, follow the what does $1000 get you thread.

On the monster track tank, the filler cap area was total crap on the sample parts we got. There are a number of issues, but a fundamental one is that the 3 holes didn't line up. In part 1, I removed the "filler cap plug" from the mold. The goal is to create a new one and have that welded in.

So I've got all kinds of parts laying around... metal tanks, oem nylon tanks, filler caps, filler cap "carrier" from a metal efi tank, 2 different brands of aftermarket filler lids, and the 3 sample tanks made from the mold already.

Measuring all this crap isn't easy, but I remembered this theorem from 7th grade:

(source)

So I wrote down all the distances from the triangle points that I could find parts for and systematically entered them all into some free open source CAD software:


Then make a circle from the 2 bottom points and the intersections from the "compass" arcs... which I then used to move each layer so as to center ALL of the measurements concentrically by their centers. (initially, they were all centered on the point in the bottom left corner)




Tweak it and superimpose over a picture of the part to be replaced... which I printed and will write notes all over it when I get into the shop tomorrow.


Full size version of all pics can be found in the Cycleworks gallery.

[erkishhorde]

Wow, those are way off! Good to see that you're making progress.  Math is your friend.... sometimes...

[ellingly]

Wow, those are way off! Good to see that you're making progress.  Math is your friend.... sometimes...

Maths (yes, I'm Australian. We spells it like that) is always your friend. Your enemy is always one's lack of knowledge of what's required .

[MotoCreations]

Alternative opening is to have gone with the older (and larger) S4/S4R/supersport mounting system with seperate casting about the gascap itself.  You'd just have to machine the lip/opening itself and forget about the intricate mold/casting part for the gascap which you are dealing with now.  Although a larger diameter, it would allow you to put a quick fuel break opening(s) in instead or other fuel delivery systems.

[krista]

Yeah, but then I have to create and sell the "flange" with the tank to sell to the majority of buyers. I could make a part that bolts on to the mold if I really need a dry break.

[Capo]

Chris, how does the 'roto' moulding process work. I assume some level of pressure is involved given the substantial construction of the mould.

[krista]

Rotational Molding wiki

Not really any pressure (I think), but something like 8 pounds of powder goes in the mold then it's bolted to a platter that spins and then goes in an oven. They have 3 or 4 arms on a machine and they typically go through 20 minute cycles. The plastic melts and then fully coats the inside of the mold.



The boxes in the foreground are their supply of the cross-linked polyethylene pellets. Those boxes are 4 feet cubed and are in all sorts of colors. Just behind the boxes, you see the two round platters on an arm... they will bolt as many molds as practical to the platter to maximize production. The big blue box behind it is the oven.

You can see freshly produced products in the distance. The yellow things are housings for the big crazy fans that carpet people bring in when your house floods. Every time I've been in there, they've had a semi trailer's worth of those things in various colors stacked up ready to go. This plant is the cleanest one I've ever seen.

Chris

[clubhousemotorsports]

I agree with motocreations on using a large flange. would it be possible to just mold it to take an oem cap flange?
then you would be able to use any oem style cap you wanted or already own. Just make the flange large enough to seal with an o-ring like the bottom of the newer tanks.

[krista]

would it be possible to just mold it to take an oem cap flange?

Yes, that is exactly the point. Their attempt at making the mold work with OEM type filler caps didn't work out so well. The bottom 2 screws are ok, but the top one is 3mm off to the right. Further, they didn't align the filler cap portion in line with the bike; it is rotated to the right a little. I believe they most of that work in the casting itself!! When I make the new replacement part, I'll use exact coordinates to machine the holes. (which is why there are X,Y values in the pic above)

I also have to make fixtures to handle when the part is pulled from the mold to help control shrink while cooling.

Chris

[Norm]

If you're going to put this project in the profit column, you're going to have to sell a hell of a lot of them.

[krista]

We got the sample tank from the molders ... the lid is PERFECT. All that work earlier was worth it.

While designing the new filler portion of the mold, I thought about how to position the cutter for the latch and came up with the drawing, which then morphed into the parts bolted to the end of the air grinder.

To find an air grinder, I walked through Lowe's and noticed that they all had the "guards" or trim parts removed, so you could see how things affixed to the tool. The kobalt was the cheapest one and also conveniently had threads, which also had two flat faces ground into them for locating. I took 2 pieces of scrap aluminum tubing left-over from other projects and I saw in my mind how they could be a guard and locator at the same time. The shield is close enough to the diameter of the fuel opening that it has restricted movement. Also, it prevents the bit from grabbing and walking around the hole.

The three black screws are japanese-type master cylinder reservoir 4mm screws. I threaded the end 1/4" of the inner part and then drilled the offset hole for the locking screw. It not only locks the collar on, but also it adds a little bit of tightening torque. What you can't see is that I had to machine a slot in the inner collar so you could tighten the arbor holding the router bit. That took a while... and I was a bit stuck as the threads to the body are smaller than the diameter of the bit. Then I machined the outer sleeve and tweaked it as needed to finally work exactly how I wanted.

This was actually pretty fun & I'm quite glad it worked on the first try. 



Oh, wait, not yet. I have the mold being polished and then I have to re-machine the filler and the bottom plate. The filler is being machined to take a teflon insert to allow powder to be poured in. The bottom is getting machined so that we can install the fittings for carby monsters' fuel level sensors. YUP! That's right, the first run will be for 1994~2001 carb'd Monsters as well as for plastic tankd (non-testa) monsters. I already have someone working on the part I'll need for the S4Rs and metal tank'd injected monsters.

Then it'll be. 

But wait, there's more... MSRP is $430!!  I'm planning on an MSRP of $499. Once I look at the numbers, I'll try working it down more. But the price won't be over $499.

OK, then it'll be 

[Hans Hergesheimer]

Well if you don't like doing math, you can always make friends with someone who owns one of these :

http://www.faro.com/contentv2.aspx?cid=1&content=misc&item=1495&ct=us

You can measure pretty much anything within 0.0004" in a 6ft diameter sphere, with the ability to move it and measure any size object you want.  They are really easy to use .