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Old Mar 02, 2014, 11:40 PM
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United States, MN, Shoreview
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Home built foam cutter thread

I was thinking of starting a thread about building DYI foam cutters. There are a lot of different methods out there and I hope this can be a place where people will discuss different ideas and show us their creations. They have been covered multiple places on RC Groups scratch built foamies is a good place to bring it up.

I finished a couple of hot wire cutters Iíve been planning for a while. I still plan to put together a smaller bow, a few more profiles for the stiff wire cutter, a router base and a stationary scroll cutter. I also have nearly finished a gravity feed machine for cutting foam wing cores. Iíve got about $60 total for the power supply, two bows and the stiff wire cutter. I have maybe $20 in the gravity feed. I will post some more pictures n try to explain how I made them in case anyone wants to build one for themselves.
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Old Mar 05, 2014, 11:56 PM
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This is a six inch bow. Works nice to cut hatches and such. It's made from 1/8" plywood, PVC pipe, a few screws and a little wire. It might not be too clear how it works to tighten the wire. The wing nut adjusts the tension on the wire. It can pivot on the 1/4 20 bolt. Here is how I put it together and an example of how it works.
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Old Mar 06, 2014, 02:26 AM
BGR
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Looks like some well thought out devices. I have a pair of 10 amp Staco Vibratory feeder bowl rheostats but they are 110 VAC so way to powerfull. I think I can hook the Staco up to a battery charger output and regulate the power that way. Just gotta build a bow and give this a try.

What kind of wire are you using?
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Old Mar 06, 2014, 01:30 PM
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Looks like some well thought out devices. I have a pair of 10 amp Staco Vibratory feeder bowl rheostats but they are 110 VAC so way to powerfull. I think I can hook the Staco up to a battery charger output and regulate the power that way. Just gotta build a bow and give this a try.

What kind of wire are you using?
For the 6" and 36" bows I use #16 guitar string. For the other one I use .032" music wire available at a local hobby store. It is stiff and can be bent to ant shape. I'm still experimenting with it. I find it should beat least 10" long. shorter than that and it seams too draw too many amps.

I think the rheostat you are describing would work well to regulate the current into a battery charger. You are right in thinking it shouldn't be run straight through 110 AC. Sounds like a fire or shock waiting for a place to happen. If you do try it, put the rheostat before the battery charger to reduce the current into the battery charger, not after to reduce the output to the bow.
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Old Mar 06, 2014, 01:41 PM
BGR
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Originally Posted by psychedvike View Post
For the 6" and 36" bows I use #16 guitar string. For the other one I use .032" music wire available at a local hobby store. It is stiff and can be bent to ant shape. I'm still experimenting with it. I find it should beat least 10" long. shorter than that and it seams too draw too many amps.

I think the rheostat you are describing would work well to regulate the current into a battery charger. You are right in thinking it shouldn't be run straight through 110 AC. Sounds like a fire or shock waiting for a place to happen. If you do try it, put the rheostat before the battery charger to reduce the current into the battery charger, not after to reduce the output to the bow.
I would have to check the Battery chargers design to see if reducing the input power will work. These rheostats are simply a wire wound variable resistor and do not care if AC or DC is input. I will have to experiment with it a little.
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Old Mar 06, 2014, 05:30 PM
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Here is mine for cutting cores. Did a good job on the test wing now to cut my 48" FPV wing with a small skinny center section! Here are some pics. I will try and video my next cut and post it here as well.

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-Ben
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Old Mar 06, 2014, 05:32 PM
FPV Proximity is FUN!
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Also wire is steel fishing wire I love this wire haven't had a piece snap on me yet
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Old Mar 06, 2014, 05:41 PM
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Home made carving tools:


Chop saw/stationary bow made from drawer slides:


I have a 48" bow made from hardwood and smaller ones made from hacksaw and coping saw frames. Best wire I've found so far is Rene wire from Jacobs online.
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Old Mar 06, 2014, 06:45 PM
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[QUOTE=fOaMmaSh87;27711149]Here is mine for cutting cores. Did a good job on the test wing now to cut my 48" FPV wing with a small skinny center section! Here are some pics. I will try and video my next cut and post it here as well.

Ben the wire fixed on one end has always looked like a great way to make tapered wings. It is definitely on my list of projects to do. I would really like to see yours in action. I look forward to the video.
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Old Mar 06, 2014, 07:06 PM
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Originally Posted by Granted View Post
Home made carving tools:

Chop saw/stationary bow made from drawer slides:

I have a 48" bow made from hardwood and smaller ones made from hacksaw and coping saw frames. Best wire I've found so far is Rene wire from Jacobs online.
Granted your caring tools are outstanding. They are simple and I bet you have excellent control over the cut. What type of wire did you use to make them? Do you know how many volts and amps the pull. Iím curious if my power supply will work if I made some like yours. Your chop saw is also very ingenious.
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Old Mar 06, 2014, 07:36 PM
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where do you guys get the templates for your wing cores? and what template making material do you prefer to use?
i plan on using that drawer hanger system with a base to carve wing cores
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Old Mar 06, 2014, 10:04 PM
serial scratchbuilder
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@psyche - I used .035" mild steel welding wire for the carving tools and my ghetto power supply will run them, no idea what they draw.
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Old Mar 07, 2014, 12:00 AM
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where do you guys get the templates for your wing cores? and what template making material do you prefer to use?
i plan on using that drawer hanger system with a base to carve wing cores
You can do a google image search for airfoil or wing cross section and you will get any type of airfoil you can imagine. From there copy the image and use your favorite program to size it to your needs. I use word. The scale on the top and side of the page makes it easy to get it sized to fit my needs. Save the file and then you can print them anytime you need. Cut it out and trace it onto your template.

I make the template out of many different things. If I'm gonna make a lot of them I use scrap 1/8" hard board or aluminium. For just a couple of cores, thick card stock or aluminium flashing works well. It's also easy to cut it out with a scissors. Two sided tape works to hold the templates on the foam. The main thing is to not have the template move during the cut.

I'm going to take some pictures of my gravity feed I use with my bow to cut wing cores as soon as I get a chance. It dose a very good job cutting cores.

When you get yours going post some pictures I'd like to see it.
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Old Mar 07, 2014, 12:02 AM
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@psyche - I used .035" mild steel welding wire for the carving tools and my ghetto power supply will run them, no idea what they draw.
Thanks Granted. I'm going to try to make some like yoursand see how they work with my battery charger power supply.
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Old Mar 07, 2014, 02:31 AM
FPV Proximity is FUN!
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Yep I will surely video it for you I just added a spring near the pivot point to keep the tension. (Mums idea)

-Ben
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