Discussion in 'High Power Rocketry (HPR)' started by ptrocketry, Jul 17, 2013.
Take a look. I am Interested also.
It's like blackbrant's calendar, there are many silent people that would buy a product but just don't speak up. I'm in a life transition right now so this would be a future product for me but I am interested...
What sizes? This wasn't my final version, my final version they were slightly oversized for the body tubes (4" was 4.125" OD) and I used a separate pair of set screws to center it on the rocket. I just didn't want to rely on a perfect cut when body tubes vary. Also, if someone fiberglass wrapped the airframe that would exclude them from using it.
Edward, I believe this is a great product with lots of potential demand. What is the minimum demand necessary?
For me 6", 4", 3"
38mm, 54mm, 3", 4", 6"
In terms of demand, I would buy all of these right now if available.
I'm not sure I have the best approach to solving this problem. The guides I have work well for 3, 4 and 6 holes. I'd have to add an index to do 8 so that you line it up with a previous hole. I'm trying to come up also with a way to make this a bit more modular. I envision attaching something that self centers to the rocket then attaching your template jig to that. But again that is way more complex.
My other idea to to use an oversized aluminum tube, for 75mm it would b 3.25" ID x 3" long. It would include six set screws to align it and hold on the rocket (3 at the top, 3 at the bottom). Drilled into the aluminum would be guide patterns for 3, 4, 6, 8, 9. The holes would be oversized and you'd use a drill guide in each hole. This would prevent you from rounding out the hole and if you need you can get a new spacer. Something like this would cost more, though.
You can buy drill bushings made from hardened steel and precisely sized for whatever drill you choose from McMaster-Carr or Enco. I've used those in hole-drilling jigs for 80-20 extrusions and after several hundred holes there's no sign of any wear.
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The one downside to drill bushings is the cost. A 1/4" OD x 1/16" ID drill bushing runs between $8-12. Much more than I believe the market will bear for this product.
Any thoughts on aluminum vs the original idea?
Why not 3D print radial guides planning for a metal drill guide/bushing sized for a small, nominal hole size (say sized for 2-56 shear pins)? With the small, pilot hole drilled, a larger hole can easily be made without affecting alignment.
Mark - that is exactly what these guides are. They will drill a 1/16" hole where you need them and then you enlarge them as needed. I know 3D printing is the hot thing right now, but I can easily beat a 3D printed guide all day with a CNC machined aluminum guide - and the aluminum will be much more durable.
Here is a rendering of the aluminum guides - this one is for 75mm/3inch rockets. It is 4 inches long. It has two sets of drill guides, one is for near the edges of airframes and one is for the interior of the airframes. It has guides for 1, 2, 3, 4, 6 and 8 holes equally spaced around an airframe. You put it around the airframe and then use six 10-32 set screws to center the airframe and hold it on. Then you use a sleeve that is 1/4" OD x 1/16" ID to drill 1/16" pilot holes. Once you remove the guide you can enlarge the holes to what you need.
I'll get prices on these if people are interested. I'm planning on 38mm, 54mm, 75mm and 98mm. To make it economical I'll probably need orders for 10 of each size. I just can't machine single ones and make it worth it to start.
I'm going to work on prices for the aluminum version - speak now or forever hold your peace.
I am in!
Would be interested.....
I'm getting prices together - but I suspect it will be above what the market will pay.
What ballpark are we talking about?
I know my material costs, but I'm working on the machining costs. I won't know until I get that done, which takes a bit because real life gets in the way. My target for 75mm is less than $20.
For a tool that I will use for years with all future 3" kits, I would pay anything $20 and under. Looking forward to this!
Interested in a 3" version
I'd be in for a 3" and a 54mm for sure, if available sub $20.
$20. Dam that's cheap. I'll be all over it.
Yup. Cheap. I would take one.
I figured out my prices and I definitely can't do it for $20 or less. I'm going to contact a couple shops and see if they can. The problem is that I'm not making enough of them to bring the cost down. I doubt I'd sell 100 in a year, so I'd just have stock sitting on the shelves.
I was wondering how you were going to pull that off.
It was my goal, but I couldn't get there. I'll see if a couple other shops I regularly use can do any better.
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