Cost Rules - Discussion of New 2009 Rules

[Julia - Running Snail]

Thank you for the answers Mr. Riley. And also thank you for updating the tables.
Julia

[Tobias]

Hi Mr Riley,

we are in the final phase of our cost report and this questions arose:

1. The "Weld - Round Tubing" process does not have a "Tooling required" indicator. As we were penalized for not using a tooling with that process last year we expect the table is wrong - meaning the tooling is required.

2. Process "Sheet metal punching": the unit used is cm^2. Is that the area of the final part, of the raw material or the lateral area (cross section of the cut, (lenght of cut*depth)). If it is the finished part, it's a little strange the part gets cheaper, the more holes you punch into it.

3. Material "Hose, rubber": Is listed twice, with one of the entries only taking into consideration the diameter and not the lenght of the Hose, which we think is quite clearly wrong but in terms of cost far cheaper for us to use. May or may not we use clearly wrong entries?

4. Rims/Process "Spinning, Metal": We were very proud to have developed and built special 2-piece alumnium hollow rims. However when we cost these the total cost just for spinning the wheel shells sums up to approx 900 usd per Wheel. For example the Inner Wheel Shell:
Process Use UnitCost Unit Quantity Multiplier Mult. Val. Sub Total
Spinning, Metal Forming inner wheel shell $0,02 cm^3 17738 1 1 $354,76

We'd like to add pictures for prove of quantity but don't want to reveal too much right now. Mabe we can send them directly to you? We calculated the volume between the material start and end position.
The cost of the final wheel (approx 1000 USD) does not at all match the prices of the bought alumnium (3-piece) wheels in the materials table. This is a little bit strange as spinning is a quite usual process for manufacturing wheel shells and made parts usually are cheaper in the CR than bought parts.

Spinning is a very efficient process so we beg you to adjust this process cost or we would have to show up with Braid Rims at the Cost-event...

Thank you!
Tobi

UAS Kiel
Raceyard

[Tobias]

Hi again,

5. We encountered some dificulties costing CFK parts: There are for us 3 possible ways to determine the weight of the cfk used:
a) We look up the density for cfk-parts in the internet and let Solidworks calculate. The weight calculated is 2 times the weight of the finished parts - so this is obviously wrong but I included it so you know we took it into cosideration.
b) We know our ply weights e.g. 200g/m^2 we know the area and the number of plies. This gives a conveniently low weight/price, as the weight of the resin is not included.
c) We take the laminated parts and put them on a scale. The weight of the resin kicks in and our total cost is about twice what we got with method b.

Hope to hear from you soon,

Tobi

UAS Kiel
Raceyard

[Thrainer]

Hi Tobi,

"Carbon Fiber, 1 Ply" in line 167 of the Materials table has the comment "Dry or Pre-Preg. Both include resin. Hand trimming allowed."

So it's clear that the complete weight of the part including the resin has to be priced with 200$/kg.

If you use a density of 1.5-1.6, your calculation with the volume should be correct, as long as the thickness and shape are like in the CAD.

900$ per wheel is indeed quite expensive, I would guess you can get one pair of TUG CFRP wheels for that.

For further questions, I suggest you use the 2010 thread.

Regards,
Thomas