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Camping fan

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: SpudBlaster15 » Tue Dec 05, 2006 11:00 pm

I believe Latke was using a 50mm CPU fan in his tests, and based on the chamber fan article he also switched it off before each shot. I would expect a camping fan to be more effective at atomizing the fuel, and leaving it on during the shot seems to further increase muzzle velocity. (Probably due to the turbulence induced in the mass of air within the chamber.)

My launcher had a ratio of 1.3:1, but I recently extended the barrel length 2ft using a coupler, thus giving it a ratio of 0.9:1. Tomorrow I shall see if the gain in combustion velocity and efficiency provided by the chamber fan is as evident with a closer to ideal ratio.
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Unread postAuthor: mindtrickonu » Wed Dec 06, 2006 10:29 am

oh ok! .... the wires ARE the mounts ... brilliant ... so the next question is .. how much would it be for screws, nuts and wire ... or is it negligable .... begligable meaning 3 bucks or so .... i think this is a great way to have a really cheap powerful fan that is really easy to replace just by attahing a new one to the steel wires on the inside right?
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Unread postAuthor: SpudBlaster15 » Wed Dec 06, 2006 6:39 pm

The cost of the mounting hardware is around $2. The fan can be detached and removed (mounts and all) in roughly 5 seconds. Reinstalling it takes a little longer, maybe 10 seconds.
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Unread postAuthor: mindtrickonu » Thu Dec 07, 2006 12:07 am

awesome ... i think im going to go get some hardware this weekend and try this thing out!
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Unread postAuthor: LOSTEXAN » Fri Dec 08, 2006 11:15 pm

So does the fan just mix it up better? or what?
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Unread postAuthor: SpudBlaster15 » Fri Dec 08, 2006 11:26 pm

It has 3 functions:

1. It vents the chamber after each shot.
2. It mixes the air and fuel before the shot.
3. If left on during the shot, it induces turbulence in the flow containings the flame front(s), resulting in a faster burn rate.
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Unread postAuthor: mark.f » Sat Dec 09, 2006 7:43 am

So what size threaded rod did you use? It looks to be #6. I used that in my TB cannon, and it just seemed a little flimsy to me.

I just finished installing another fan in another combustion I'm making with 1/4-20 allthread. You have to grind the allthread where it passes through the center of the fan to allow the batteries to slide through, but it's definitely sturdy.

Did you just slide something non-conductive between one of the battery leads and a contact in the fan and then add a switch to the lead and contact? I thought about doing something like that, but in the end I didn't want a bunch of wire and a toggle switch on the outside of my chamber.

For those of you who are skeptical that these fans will work well, I'll tell you right now that they're WAY more powerful than a normal PC fan. I've been using them ever since the summer. Even when I use my friends combustion, (no fan, deodorant powered), I keep a fan in my pocket to vent the chamber after shots. The sizes it can fit in are 3", 4", and up. I know SMOMV uses one in his 8" soccerball cannon, which should tell you just about how much air these suckers push. I bet a few of these could vent and mix a 12" launcher, if you wanted them to.

Just mount them like this, or like SpudBlaster has his. Either way you can mount it will work.

<img src="http://www.spudfiles.com/forums/album_pic.php?pic_id=213&full=true&">
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Unread postAuthor: SpudBlaster15 » Sat Dec 09, 2006 1:04 pm

I used #8 screws. I originally had #6 screws in there, but I replaced them due to the fact that they were extremely flimsy. 1/4-20 screws would work even better.

The batteries are no longer mounted in the fan, they are in the barrel support. Removing them fron the fan assembly gave me lots of room to install the mounts. I simply ran wires from the motor terminals to those posts, which conduct the current from outside of the gun. This configuration allows me to use a concealed, 3 cell "pack" of AAs for a little more power. Not that the fans really need it though, they are already very effective.
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Unread postAuthor: mindtrickonu » Mon Dec 11, 2006 2:23 pm

ok well i went out to the hardware store and i bought a bunch of hardware to : mount it, wire it, turn it on and off .... i was wondering if there was a special way to drill a hole in ti to mount it centered in teh chamber or something along those lines ... also how many shots have you fired with it and is it still working ok?
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Unread postAuthor: SpudBlaster15 » Mon Dec 11, 2006 6:36 pm

Just drill the holes as best you can, and if it is not centered in the chamber just bend the mounts I guess.

I have fired it roughly 30 - 40 times since installing the fan and it is still working fine.
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Unread postAuthor: mindtrickonu » Mon Dec 11, 2006 11:28 pm

ok well i got the stuff and i started work and heres how i did it:

1. drilled a hole close ot the screws that open up the case.
2. inserted a screw thru 2 layers of PVC and into the case, just enough to hold it firmly
3.wrapped the end of a wire around a nut and made it touch against the motor casing
4.wedged the end of a wire in front of the battery plate (the one that has the metal piece that connects the battery to the motor casing)
5. cut the piece that touches the motor casing
6.ran these wires to two screws drilled in the wall of the chamber (which will be wired to a switch)
7. gotta trim the blades for fudge factor (yea i screwed up a couple things, oh well)

so....right now looking at it theres a fan hanging in the middle of the chamber with two wires coming up to screws .... thats about it...im finishing the rest tommorow and im going to see how it fires! .... yay!
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Unread postAuthor: SpudBlaster15 » Mon Dec 11, 2006 11:41 pm

Sounds like it will work just fine. How solid is the mount to fan connection?
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Unread postAuthor: mindtrickonu » Tue Dec 12, 2006 12:21 am

its pretty solid .. i maybe screwed it in about three or four threads and did the ol's shake it really hard test and it seemed fine.... note that the shake it realy hard test is for the most dire of conditions (like dropping the cannon from waist level etc.) ... im going to put some CA super glue in there just for good measure ... then duct tape it and arc weld it
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Unread postAuthor: mindtrickonu » Thu Dec 14, 2006 12:16 am

ok i have it all wired up and it works great!! ... i just test fired it about 15 minutes ago
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Unread postAuthor: SpudBlaster15 » Sat Dec 23, 2006 11:53 am

Well, my camping fan's motor suddenly stopped working for no aparant reason, so I bought 2 more. Both stopped working after 30 seconds. The batteries are all fine, and after disassembling them, everything appears to be in tact, so I suspect an issue with the internal motor parts.
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Last edited by SpudBlaster15 on Sat Dec 23, 2006 1:20 pm, edited 1 time in total.
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