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Re: CDC report
Hi Elton and All,
A few clarifications:
1. Rohacell - I spoke very briefly with Dan Carman about this at the
meeting. He is using it for the FDC mounting and is not having any
problems with crumbliness as he is not machining it. The
construction/machining problems that Curtis mentioned below are enough to
rule out Rohacell, but the added crumbliness would make keeping the system
clean during construction a nightmare! We'll keep thinking about it,
though.
2. Honeycomb Al - The mention of this material in my talk was merely
that it is the lightest and stiffest. There are still a few construction
issues that need to be looked at. This is most likely not the ideal
material.
3. Carbon Fiber - Gary has just finished riddling our 4mm carbon fiber
sample with holes, and it feels pretty darn stiff. He will be testing
all of the machined samples soon to give us an idea of just how stiff.
More info as we get it...
Thanks for adding me to the tracking list. Much appreciated.
-Mike
On Mon, 2 Apr 2007, Curtis A. Meyer wrote:
> Hi Elton -
>
> the Rohacell has other issues. The design that we had
> considered had us inserting the tubes into a Rohacell
> holder. Because the tubes physically touch, this would
> have required the drilled holes to all connect and the
> endplate would fall apart.
>
> We did not consider a composite with skins, but at this
> point you get to the skin being the dominant material. I
> have not had a chance to write things up yet, but we are
> looking at several possibilities:
>
> 4mm G10 (have material in stock)
> 6mm Delrin (not sure we can get a big enough sheet)
> 4mm Carbon Fiber (special order to get it big enough)
> Aluminum Honey Comb (skins get fairly thick for the stereo)
>
> What we are doing is measuring "stiffness" before and after
> drilling, and have data on the above. While the Delrin is not
> real stiff, if we could support it during stringing, it would be
> good. I am actually not convinced of the Aluminum Honeycomb,
> but we have it and are looking at it.
>
> What we found with the Rohacell was that it was quite "crumbly",
> little pieces falling off the edges. We could put a skin on it, but
> it needs to be about 2.5 to 3mm to support the stero. This is not
> too different from some of the materials we are looking at above.
>
> I am convinced that we will have an endplate that has substantially
> less material than the 6mm Al in the current design. I am just not
> 100% sure of what it is yet.
>
> - Curtis
>
>
> On Mon April 2 2007 14:31, Elton Smith wrote:
>>
>> Hi Curtis,
>>
>> I noticed today that Mike had prepared an update on the CDC for the
>> collaboration meeting, although it was not presented. This is likely
>> because it was scheduled originally and the lack of time. However, I did
>> briefly take a look at it and have a question about the downstream
>> endplate studies. One of the conclusions is that Rohacell will not work
>> but the honeycomb is the most rigid. Since this was not discussed, I do
>> not know if this was considered as a composite with skins. Clearly foam
>> alone would not be sufficiently rigid, but our experience is that a foam
>> composite with carbon fiber or stainless skins is as rigid as honeycomb
>> and more uniform. Accuracy in drilling can be established in the skins
>> with oversized holes in the foam.
>>
>> Cheers, Elton.
>>
>> p.s. I have also noticed that no one from the CDC group is subscribed to
>> the halld-tracking-hw list and I have taken the liberty to add you to the
>> list. This is one of the primary communication mechanisms for drift
>> chamber discussion.
>>
>>
>> Elton Smith
>> Jefferson Lab MS 12H5
>> 12000 Jefferson Ave
>> Suite # 16
>> Newport News, VA 23606
>> elton@jlab.org
>> (757) 269-7625
>>
>
> --
> Professor Curtis A. Meyer Department of Physics
> Phone: (412) 268-2745 Carnegie Mellon University
> Fax: (412) 681-0648 Pittsburgh PA 15213-3890
> cmeyer@ernest.phys.cmu.edu http://www.curtismeyer.com/
>
>