Super Soaker Central forums

tim jones · 04-08-2008, 02:00 PM

I need to define my terms more precisely. The desired change in inside diameter is 1.000" - 0.125" = 0.875", so the desired length of the conical section (with 1:8 taper) is 8 * 0.875" = 7.000".

I'm not having much luck finding an appropriately tapered female mold of adequate size. Perhaps I'll finish the mandrel first, and build the female mold from it, using fiberglass and epoxy.

Silence · 04-08-2008, 09:14 PM

Yeah, I got confused. I was thinking of it one side at a time - since the nozzle is symmetrical, you could do 1/2" - 1/16" = 7/16" and then multiply by 8. But when you put the two together, which I forgot to do, it become 1:4 instead. Whoops. Sorry about the confusion.

6061 · 04-09-2008, 02:38 AM

I still think that your best bet is to use wax, you may find a candle with dimensions that are very close to that and then fiberglass around it, but to turn that shape isn't going to be easy, the rigidity at the small end will definitely cause issues.

As for sand casting, basically all valves housings, larger brass shapes, and even most engine blocks are made through sand casting. Basically you take an object, mold sand that is impregnated with oil all around it, remove the object, and pour liquid metal into the cavity. The threads and mating surfaces are machined after to ensure a good fit. It is a cheap and easy manufacturing method, and the sand can be reused many times.

tim jones · 04-10-2008, 12:38 PM

The mandrel has been turned, and it ended up with about 9-1/2" taper. The tip is 1/8" off center, so the blank must have been slightly skewed in the chuck. The finish is much smoother than I expected, so filling and sanding will be at a minimum before casting the female mold.

In related news, the last of our Latex Rubber Tube (3/8" ID x 3/4" OD x 5', and 3/4" ID x 1-1/8" OD x 5') arrived from McMaster-Carr this morning. I'll probably finish and test the pressure bladder before I mess with the mandrel any more.

EDIT:
04/11/08 I spent my 45 min of free time last night fixing the ecentricity of the mandrel. It now has a 9-1/4" taper, the tip is 1/16" dia, and the tip is within 1/32" of the center - good enough for government work.

04/14/08 The good news is that I finished casting the female mold over the weekend. The bad news was that it appeared to be cemented to the mandrel. I pressed off the mold with the hydraulic press in Maintenance. This damaged the tip of the mold, but it is still usable. The mandrel is badly warped from absorbing moisture from the mold release. I think this is what caused it to get stuck to the mold. I'll have to see if it straightens out when it dries.

In other news, the 8" LRT bladder is complete and installed on the gun. The pump is also finished, but needs a pair of check valves for a pressure test.

Ben · 04-23-2008, 07:16 PM

Hmm... never noticed your edits to this thread. Any more news? Have any better success in making a mold?

tim jones · 04-28-2008, 02:18 PM

Sorry i haven't posted progress in a while. I was out of state for the rest of the week after the 14th, and my wife had shoulder surgery last week when I got back. I haven't had much free time till yesterday.

The wooden nozzle mandrel has been drying for two weeks, but still had a bit of warp when I checked it this morning. I'll try to use it as-is. The female mold is dry, and its internal surfaces are fairly rough from the process used to separate it from the mandrel. I'll just have to try it on Wednesday and see how it goes, but I may need to turn another mandrel out of something like UHMW next week.

In other news, the basic watergun is nearing completion. It has a 3/8" ID x 1-1/8" OD x 8" pressure bladder, a 4" threaded case for the pressure bladder, a 1/2" dia. x 16" pump, and a 5-gallon backpack. It still needs a 1" nozzle (obviosly), a charging handle for the 1" ball valve, a sling, and a pistol grip (or top-mounted tote handle - I haven't decided which yet).

I performed a pressure test and leak-check yesterday. The bladder expanded to 3-1/4" dia. x 20" long, but at only 40 psi. I expected a slightly larger diameter (3-3/4" to 4-1/8", using the 8-9 x ID + wall formula) and higher pressure (60 psi), since the inner LRT is rated at 35 psi and the outer LRT is rated at 25 psi. Do past experiences indicate that the bladder will still hold more water, or that it will pop?

Ben · 04-28-2008, 04:25 PM

No problem.

The 800% increase in diameter was removed from McMaster-Carr a few years ago. (I think it was 800% at least.) It might only apply to smaller diameters. I might have to look at a stress vs. strain curve for latex rubber to figure out where it stops expanding substantially.

The pressure figures don't add like you expected. The pressure is a function of the thickness and the inner diameter. Smaller inner diameters and more thickness result in more pressure. The pressure figures on LRT are for their own inner diameter, not the smaller tube's one, so for that reason alone you can't add them. Also, if you examine the pressure ratings of LRT, you'll see that you get diminishing returns for larger thicknesses. So it's not surprising that you get pressures around 40 PSI, which should be plenty adequate. I'd suggest layering bike tubes over that to increase the pressure more if you do want more pressure. Two layers of LRT plus 10 or more bike tubes is very strong.

A few months ago I tried to figure out a function to approximate the pressure of LRT, but the data from McMaster-Carr was both inconsistent and imprecise, so I decided to put it off until later. Figuring out an equation may not be an easy task. Rubber doesn't follow Hooke's law from what I've read, so I'd have to learn some new stuff. We might get lucky and some Hasbro or Buzz Bee Toys engineers could come and explain too.

I had planned and outlined a page about LRT, so these basics will be covered in a new article in a month or two.

tim jones · 05-01-2008, 01:09 PM

I attempted to thermo-form a nozzle from 1" SDR-21 (200 psi thin-wall) PVC pipe last night, using the wooden mandrel and female mold. The attempt can only be categorized as a "learning experience", failing to produce a usable nozzle.

The problems are mostly with the female mold. Damaged sections of the rim at the larger end of the cone tended to catch and buckle the softened pipe end, rather than compress it into a conical taper. I bevelled the damaged end to about a 1:5 taper with my Dremmel and tried again, but with the same result. The pipe end would start to form, but would drag on the rough mold interior and buckle the pipe just outside of the mold. I'll need to make a new conical mold with a mouth that is slightly larger than the pipe OD, and with smoother interior surfaces. Fiberglass and epoxy is starting to look pretty good.

Another interesting note is that the softened pipe, when removed from the female mold, springs back to its full initial OD. To form a nozzle, I'll need to hold the pipe in the mold until it fully cools.

I've got a busy weekend comming up, but I'll start work on a new (and improved!) female mold.

aEx155 · 05-02-2008, 11:36 PM

This is slightly unrelated, but related at the same time...

http://www.orbitonline.com/products/Tools/02/49/22/440/

Has anyone tried using these as nozzles?

Silence · 05-03-2008, 12:41 AM

Wow, that at least looks effective. I'm guessing the aperture is 1/8", and I'm sure it's less than 1/4". The question is, in that product, is the conical piece actually used as a nozzle? Or is it part of the rest of the device?

I see a tube with the cone on it underground in one of the pictures. I'll investigate further tomorrow...it's late.

aEx155 · 05-03-2008, 09:41 AM

I did see one of these at Home Depot one time, but I didn't get a chance to measure it. I wasn't thinking about it that time...

When you use it for it intended purpose, you would take your piece of pipe, cut it to longer than the thing your tunneling under, then cement the two parts to the pipe. Then you would dig two holes on either side, hook it up to your hose and use it to blast away the dirt from one hole until you reach the other side. Then you can cut off the tunneling parts and install things on the pipe as necessary.

Code:

        _____           _____
= pipe, ///__ hose end, _____> nozzle end
______                                  _____
///_======================================___>

Of course, for out purposes, we would just make it so the two halves are right next to each other to use it as a (albeit long) nozzle.

Code:

__________
///_====__>

Silence · 05-03-2008, 06:57 PM

I think I get it now. Thanks. It seems that piece could be a viable nozzle after all. And it combines the size of small pipe nipples and the shape of firehose nozzles, which is also a good sign. The next question is whether the end of the orifice has parallel walls - if there's a taper all the way through, the stream could be rather turbulent. It's not a big deal underground but it is when in the air.

aEx155 · 05-03-2008, 10:46 PM

When I get the chance, I'll drop by Home Depot and look at it. Hopefully this has some promise.

tim jones · 05-07-2008, 01:43 PM

I made a conical mold out of sheet metal over the weekend. It was made from a long triangular piece, simply formed over the wooden mandrel and spot-welded. The ID of it's large end is about 1/4" larger than the pipe OD. I used this mold in another failed attempt to thermoform a nozzle from PVC pipe.

The pipe end would start to form, but would adhere to the mold interior and buckle the pipe just outside of the mold.

I wonder if the pipe is just not hot enough to soften the plastic sufficiently for forming? I'll try again, this time heating the pipe in oil instead of water.

04-08-2008, 02:00 PM	#16
tim jones Junior member Join Date: Mar 2008 Posts: 12 UserID: 1480	Re: homemade nozzles I need to define my terms more precisely. The desired change in inside diameter is 1.000" - 0.125" = 0.875", so the desired length of the conical section (with 1:8 taper) is 8 * 0.875" = 7.000". I'm not having much luck finding an appropriately tapered female mold of adequate size. Perhaps I'll finish the mandrel first, and build the female mold from it, using fiberglass and epoxy.

04-08-2008, 09:14 PM	#17
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: homemade nozzles Yeah, I got confused. I was thinking of it one side at a time - since the nozzle is symmetrical, you could do 1/2" - 1/16" = 7/16" and then multiply by 8. But when you put the two together, which I forgot to do, it become 1:4 instead. Whoops. Sorry about the confusion. __________________ Forum rules

04-09-2008, 02:38 AM	#18
6061 Junior member Join Date: Mar 2008 Location: vancouver Posts: 9 UserID: 1485	Re: homemade nozzles I still think that your best bet is to use wax, you may find a candle with dimensions that are very close to that and then fiberglass around it, but to turn that shape isn't going to be easy, the rigidity at the small end will definitely cause issues. As for sand casting, basically all valves housings, larger brass shapes, and even most engine blocks are made through sand casting. Basically you take an object, mold sand that is impregnated with oil all around it, remove the object, and pour liquid metal into the cavity. The threads and mating surfaces are machined after to ensure a good fit. It is a cheap and easy manufacturing method, and the sand can be reused many times.

04-10-2008, 12:38 PM	#19
tim jones Junior member Join Date: Mar 2008 Posts: 12 UserID: 1480	Re: homemade nozzles The mandrel has been turned, and it ended up with about 9-1/2" taper. The tip is 1/8" off center, so the blank must have been slightly skewed in the chuck. The finish is much smoother than I expected, so filling and sanding will be at a minimum before casting the female mold. In related news, the last of our Latex Rubber Tube (3/8" ID x 3/4" OD x 5', and 3/4" ID x 1-1/8" OD x 5') arrived from McMaster-Carr this morning. I'll probably finish and test the pressure bladder before I mess with the mandrel any more. EDIT: 04/11/08 I spent my 45 min of free time last night fixing the ecentricity of the mandrel. It now has a 9-1/4" taper, the tip is 1/16" dia, and the tip is within 1/32" of the center - good enough for government work. 04/14/08 The good news is that I finished casting the female mold over the weekend. The bad news was that it appeared to be cemented to the mandrel. I pressed off the mold with the hydraulic press in Maintenance. This damaged the tip of the mold, but it is still usable. The mandrel is badly warped from absorbing moisture from the mold release. I think this is what caused it to get stuck to the mold. I'll have to see if it straightens out when it dries. In other news, the 8" LRT bladder is complete and installed on the gun. The pump is also finished, but needs a pair of check valves for a pressure test. Last edited by tim jones : 04-14-2008 at 12:10 PM.

04-23-2008, 07:16 PM	#20
Ben Founder Join Date: Mar 2003 Location: College Park, Maryland Posts: 6,054 UserID: 1	Re: homemade nozzles Hmm... never noticed your edits to this thread. Any more news? Have any better success in making a mold? __________________ email: / Forum rules / Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas.

04-28-2008, 02:18 PM	#21
tim jones Junior member Join Date: Mar 2008 Posts: 12 UserID: 1480	Re: homemade nozzles Sorry i haven't posted progress in a while. I was out of state for the rest of the week after the 14th, and my wife had shoulder surgery last week when I got back. I haven't had much free time till yesterday. The wooden nozzle mandrel has been drying for two weeks, but still had a bit of warp when I checked it this morning. I'll try to use it as-is. The female mold is dry, and its internal surfaces are fairly rough from the process used to separate it from the mandrel. I'll just have to try it on Wednesday and see how it goes, but I may need to turn another mandrel out of something like UHMW next week. In other news, the basic watergun is nearing completion. It has a 3/8" ID x 1-1/8" OD x 8" pressure bladder, a 4" threaded case for the pressure bladder, a 1/2" dia. x 16" pump, and a 5-gallon backpack. It still needs a 1" nozzle (obviosly), a charging handle for the 1" ball valve, a sling, and a pistol grip (or top-mounted tote handle - I haven't decided which yet). I performed a pressure test and leak-check yesterday. The bladder expanded to 3-1/4" dia. x 20" long, but at only 40 psi. I expected a slightly larger diameter (3-3/4" to 4-1/8", using the 8-9 x ID + wall formula) and higher pressure (60 psi), since the inner LRT is rated at 35 psi and the outer LRT is rated at 25 psi. Do past experiences indicate that the bladder will still hold more water, or that it will pop?

04-28-2008, 04:25 PM	#22
Ben Founder Join Date: Mar 2003 Location: College Park, Maryland Posts: 6,054 UserID: 1	Re: homemade nozzles No problem. The 800% increase in diameter was removed from McMaster-Carr a few years ago. (I think it was 800% at least.) It might only apply to smaller diameters. I might have to look at a stress vs. strain curve for latex rubber to figure out where it stops expanding substantially. The pressure figures don't add like you expected. The pressure is a function of the thickness and the inner diameter. Smaller inner diameters and more thickness result in more pressure. The pressure figures on LRT are for their own inner diameter, not the smaller tube's one, so for that reason alone you can't add them. Also, if you examine the pressure ratings of LRT, you'll see that you get diminishing returns for larger thicknesses. So it's not surprising that you get pressures around 40 PSI, which should be plenty adequate. I'd suggest layering bike tubes over that to increase the pressure more if you do want more pressure. Two layers of LRT plus 10 or more bike tubes is very strong. A few months ago I tried to figure out a function to approximate the pressure of LRT, but the data from McMaster-Carr was both inconsistent and imprecise, so I decided to put it off until later. Figuring out an equation may not be an easy task. Rubber doesn't follow Hooke's law from what I've read, so I'd have to learn some new stuff. We might get lucky and some Hasbro or Buzz Bee Toys engineers could come and explain too. I had planned and outlined a page about LRT, so these basics will be covered in a new article in a month or two. __________________ email: / Forum rules / Read this page before emailing me. Do not send me a PM or email with a water gun question if someone else could answer the question. Post at the forums. You will get a response from me along with others' views or ideas.

05-01-2008, 01:09 PM	#23
tim jones Junior member Join Date: Mar 2008 Posts: 12 UserID: 1480	Re: homemade nozzles I attempted to thermo-form a nozzle from 1" SDR-21 (200 psi thin-wall) PVC pipe last night, using the wooden mandrel and female mold. The attempt can only be categorized as a "learning experience", failing to produce a usable nozzle. The problems are mostly with the female mold. Damaged sections of the rim at the larger end of the cone tended to catch and buckle the softened pipe end, rather than compress it into a conical taper. I bevelled the damaged end to about a 1:5 taper with my Dremmel and tried again, but with the same result. The pipe end would start to form, but would drag on the rough mold interior and buckle the pipe just outside of the mold. I'll need to make a new conical mold with a mouth that is slightly larger than the pipe OD, and with smoother interior surfaces. Fiberglass and epoxy is starting to look pretty good. Another interesting note is that the softened pipe, when removed from the female mold, springs back to its full initial OD. To form a nozzle, I'll need to hold the pipe in the mold until it fully cools. I've got a busy weekend comming up, but I'll start work on a new (and improved!) female mold.

05-02-2008, 11:36 PM	#24
aEx155 Senior Member Join Date: Apr 2008 Posts: 315 UserID: 1517	Re: homemade nozzles This is slightly unrelated, but related at the same time... http://www.orbitonline.com/products/Tools/02/49/22/440/ Has anyone tried using these as nozzles?

05-03-2008, 12:41 AM	#25
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: homemade nozzles Wow, that at least looks effective. I'm guessing the aperture is 1/8", and I'm sure it's less than 1/4". The question is, in that product, is the conical piece actually used as a nozzle? Or is it part of the rest of the device? I see a tube with the cone on it underground in one of the pictures. I'll investigate further tomorrow...it's late. __________________ Forum rules

05-03-2008, 09:41 AM	#26
aEx155 Senior Member Join Date: Apr 2008 Posts: 315 UserID: 1517	Re: homemade nozzles I did see one of these at Home Depot one time, but I didn't get a chance to measure it. I wasn't thinking about it that time... When you use it for it intended purpose, you would take your piece of pipe, cut it to longer than the thing your tunneling under, then cement the two parts to the pipe. Then you would dig two holes on either side, hook it up to your hose and use it to blast away the dirt from one hole until you reach the other side. Then you can cut off the tunneling parts and install things on the pipe as necessary. Code: _____ _____ = pipe, ///__ hose end, _____> nozzle end ______ _____ ///_======================================___> Of course, for out purposes, we would just make it so the two halves are right next to each other to use it as a (albeit long) nozzle. Code: __________ ///_====__>

05-03-2008, 06:57 PM	#27
Silence Administrator Join Date: Apr 2006 Location: Virginia Posts: 3,293 UserID: 576	Re: homemade nozzles I think I get it now. Thanks. It seems that piece could be a viable nozzle after all. And it combines the size of small pipe nipples and the shape of firehose nozzles, which is also a good sign. The next question is whether the end of the orifice has parallel walls - if there's a taper all the way through, the stream could be rather turbulent. It's not a big deal underground but it is when in the air. __________________ Forum rules

05-03-2008, 10:46 PM	#28
aEx155 Senior Member Join Date: Apr 2008 Posts: 315 UserID: 1517	Re: homemade nozzles When I get the chance, I'll drop by Home Depot and look at it. Hopefully this has some promise. Last edited by aEx155 : 05-08-2008 at 12:08 AM.

05-07-2008, 01:43 PM	#29
tim jones Junior member Join Date: Mar 2008 Posts: 12 UserID: 1480	Re: homemade nozzles I made a conical mold out of sheet metal over the weekend. It was made from a long triangular piece, simply formed over the wooden mandrel and spot-welded. The ID of it's large end is about 1/4" larger than the pipe OD. I used this mold in another failed attempt to thermoform a nozzle from PVC pipe. The pipe end would start to form, but would adhere to the mold interior and buckle the pipe just outside of the mold. I wonder if the pipe is just not hot enough to soften the plastic sufficiently for forming? I'll try again, this time heating the pipe in oil instead of water.

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