Yup, that looks like good. Troy _____ From: sugpro-bounce@xxxxxxxxxxxxx [mailto:sugpro-bounce@xxxxxxxxxxxxx] On Behalf Of Bill Kuker Sent: Friday, 20 February 2015 1:52 PM To: sugpro@xxxxxxxxxxxxx Subject: [sugpro] Re: Srm nozzle throat size Yeah, those screenshots are from very early work. It looks like the attached screenshot now, which I think is correct. -Bill Inline image 1 On Thu, Feb 19, 2015 at 5:30 PM, Troy Prideaux <GEORDI@xxxxxxxxxxxxxxxx> wrote: The geometry regression for the c-slot geometry is incorrect – at least it looks that way. Internal Corners (convex vertices) don’t regress out as sharp corners, but as a radius. If the corner starts out without any initial radius, the center point of the radius will be the point of the corner/vertex. Conversely, concave/reflex corners will regress *in* sharply (no radius) Troy _____ From: sugpro-bounce@xxxxxxxxxxxxx [mailto:sugpro-bounce@xxxxxxxxxxxxx] On Behalf Of Bill Kuker Sent: Friday, 20 February 2015 5:47 AM To: sugpro@xxxxxxxxxxxxx Subject: [sugpro] Re: Srm nozzle throat size Yes, check out http://content.billkuker.com/projects/rocketry/software or https://github.com/bkuker/motorsim for the source code. The math is more or less based on SRM.xls, but it has more options for grain geometry. -Bill On Thu, Feb 19, 2015 at 12:18 PM, Steve Peterson <steve_peterson@xxxxxxxxxxxxx> wrote: I wrote my own--it's not that hard. Also, Bill Kuker wrote a program that is available--don't know the details, though. It's at content.billkuker.com --Steve On 02/19/2015 04:40 AM, Dan Harrison wrote: Thanks for the replies . Michael, that is a good idea with the bolt I will try that when I build my stand. Steve, is there a different software you use to sim motors? I know there is a program called burnsim but I was under the impression that was only for ap motors . Thanks, Dan On Feb 17, 2015, at 1:08 PM, Michael Monteith (Redacted sender "michael_r_monteith@xxxxxxxxx" for DMARC) <dmarc-noreply@xxxxxxxxxxxxx> wrote: One I've seen is where they pre load it with a weight and use a bolt underneath the load cell and adjust it to limit the load cell being pushed any further. Of course the bolt being locked in place once it's adjusted. That way you get the resolution by using a smaller cell but protect it from being pushed too far in the case of miscalculation or catostrophic event. Probably should be a standard procedure anyway to protect the load cell. Michael -------------------------------------------- On Tue, 2/17/15, Steve Peterson <steve_peterson@xxxxxxxxxxxxx> wrote: Subject: [sugpro] Re: Srm nozzle throat size To: sugpro@xxxxxxxxxxxxx Date: Tuesday, February 17, 2015, 1:02 PM Hey Dan, I can't answer the first question since I don't actually use SRM, but the calcs it does are pretty accurate--the real question will be how accurate/reliable is your construction? The safe thing to do, if you've never tested a motor before, is to start with a load cell that is capable of much more thrust than you anticipate your motor will produce, especially if/when it CATOs. --Steve On 02/17/2015 09:35 AM, Dan Harrison wrote: Hello ,I'm looking to find some info on using Richard nakka's srm. Is there a way to change the nozzle throat size to match my motor? I tried using the nozzle erosion box but I'm not sure if that is the right way to do it. How accurate is srm ? I realize there are a lot of variables .but generally speaking if it calculates 25 lbs max thrust is that usually close to what it will measure on a test stand? The reason I ask is I'm building a test stand and I want to make sure I put the correct load cell on for my first test. Thanks, Dan
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