Thinking of using tow hitch as an air tank.

[slomatt]

On my 2000 I have the newer style of factory hitch where there is a square tube welded to the brackets on each end and the actual hitch hangs down below. You can kinda see it in this picture.

http://www.blankwhitepage.com/gallery/albums/t4r_pardoes_20100918/IMG_1072.jpg

The tube is approx 3" square and 38" long, and as far as I can tell it is welded shut on both ends. Assuming the metal is at max 1/4" thick that means the internal volume is at least 1 gallon. I'm considering tapping some holes and using it as a tank. My two concerns are if the holes will make it less strong, or if I'm just asking for it to rust out. I would definitely shoot some paint inside and use an air/water separator to minimize the amount of moisture that is introduced.

Anybody have any reason why this is a dumb idea? :)

- Matt

[strykersd]

It just sounds like more work then it's worth. One gallon won't really help airing up, but I guess if you have a need for air tools it could be useful.

[Robinhood4x4]

Your holes will be pretty small so I don't think it'll harm the integrity much. Usually things break from fatigue and I don't think you tow enough to have to worry about it. The optimal place to drill your holes will be through the mounting brackets on the ends of the tube.

I say go for it.

[Scuba]

I'm with Patrick. That small thing just won't have much volume.

But if your itching for a rainy day project.. Who am I to stop you..
Have fun!

[slomatt]

I'm with Patrick. That small thing just won't have much volume.

But if your itching for a rainy day project.. Who am I to stop you..
Have fun!


Scuba, I agree that it won't do much to help out with airing up the tires. But, I figure if I can get this working for $20 or so it's worth it for the ability to use air tools and for the small amount of time it saves when airing up.

- Matt

[4x4mike]

Like it's been said go through the brackets. I think this could be done very easily and you'd benefit. My system only uses a 1/2 gallon tank but at idle it's the difference between being able to use an air gun to blow off or not. At about 1000 rpm I can run air tools.

For you and your MV-50 it'll give you a little reserve that will allow you to use that air gun with better results. After you drill your holes I'd shoot something in there that will coat the inside. There is a good product guys use on the beds of their lathes but I forget what it is called but I do remember it's got an aqua colored label. Go for it and post pics.

[L33T35T Tacoma]

I'm gonna have to say nay. the biggest concern would be the need for a drain cock on there (yes, I said cock). I looked in to using my rock sliders in the same fashion, and it looked like more hassle than it was worth. Plus yes, you'll run the risk of it rusting from the inside out, even though you plan to paint it, I'd still be worried.

I'd type more but I'm exhausted

[4x4mike]

If you're concerned use this: http://www.treefortbikes.com/product/333222339240/351/JP-Weigles-Frame-Saver-Aerosol.html

If you're really concerned use it twice a year. A filter isn't going to get rid of all the water in the air. It's hot coming out of the compressor and will be warm in the tank. When it cools the moisture will form. To really cut down on the moisture don't store air in the tank and drain when you're done using the air. I do this with my home compressor and everything stays dry enough that my filters aren't really used.

[strykersd]

Scuba, I agree that it won't do much to help out with airing up the tires. But, I figure if I can get this working for $20 or so it's worth it for the ability to use air tools and for the small amount of time it saves when airing up.

- Matt


It's been a while since I've done the math, but if I remember correctly a one gallon air tank, even at 100PSI won't save you much time airing up, maybe a minute or less. My other question is if there is a way to paint the inside of the tube without having to cut it up and reweld it?

[4x4mike]

My other question is if there is a way to paint the inside of the tube without having to cut it up and reweld it?

Hence the reason for the frame saver. You can spray it in and you're good to go. Cutting and rewelding won't solve anything since the rewelding will cook off all the paint in the weld zone.

[slomatt]

I've looked into this a bit more and here's an update. Mike noticed that there were black stickers covering holes on the sides of Ken's hitch, and when I checked I had the same setup. The holes are 14mm in diameter which means that the smallest NPT fitting that would fit is 3/8", which is fine since you can just install a 1/4" adapter. The problem is that for some reason the edge of the hole overlaps with the rear part of the hitch tube by about 1/8" or so. In other words, the edge of the hole is blocked on the inside by the hitch tube. This is a problem because NPT taps are tapered and I'm not sure you can buy a blind NPT tap, and even if you could I'm not sure it would seal properly because of the taper.

So, what to do about this? Here's the options I've come up with and I'm very interested in hearing other people's input.

A. Use a die grinder to "hog out" the part of the hitch that overlaps. I'm not sure this is really possibly since a 3/8" NPT tap requires a 9/16" hole which is 14.3mm. I'd have to remove about half the wall thickness with the grinder, and then keep the tap straight enough that it threads the wall a bit.

B. Somehow seal the holes and drill new ones, but sealing the holes enough to hold ~110psi is going to be tough. If I had a welder, no problem, but since I don't have one I'm looking for other solutions. I guess I could fill the hole with JB weld and then JB weld a plate over the top. Ideally I'd put a bolt through it with a washer on the outside and silicon to seal it, but how to hold a nut in place on the inside?

Any other ideas?

- Matt

[4x4mike]

I'm going to grab some lunch and mull this over.

[Seanz0rz]

i was thinking about this the other day. is it the 3 piece model with two side brackets and a main bar with 3 bolts a each end, or is it a solid piece? mine is a 3 piece and the ends of the middle bar with the hitch, are open.

i dont think you are going to accomplish this without a welder. ideally you would weld up the existing holes and drill and tap new ones. then pressure test in a bucket of water and weld up any leaks.

[slomatt]

Sean,

This is the one piece model where the ends are welded to the cross bar and the hitch mounts below the cross bar. I've inspected the welds and can't see any holes. The only openings into the cross bar are at the ends and those are welded to the side plates.

- Matt

[4x4mike]

Matt, let's say you welded the existing holes shut. Would the "tank" be sealed? As in, is the middle section welded all the way around the side plates? I'm thinking it is but the image I paint in my head of the situation you described makes me wonder.

I think hogging out the hole with a die grider would be a PITA and might not work. Those side plates are pretty thick.

This is just me thinking out loud but if it were me I'd try to close the hole up a little. I'd weld the hole on the side where there is the 1/8" overlap. Then make the hole a little larger in the opposite direction. It's most likely easier said than done and really I haven't tried to tap a hole I've welded shut although I know it's common practice especially when threads go bad. In the end the hole will be more centered and you'd be able to tap it properly. Another option would be to source some NPT bungs and weld them over the hole. It still requires welding and would probably be a little easier. With my little welding skills I'm sure I get the bung too hot and warp it in and effort to make an airtight weld but maybe you can find someone who could make it happen. I guess if you could find that person you might as well have them weld the holes shut and you just drill some new ones anyway.

Jb weld may hold as you described. Back in my first summer before college I made some PVC tanks and used JB to hold some caps and fittings. In the end it didn't hold up but only because of the slight expansion that occured when you fill PVC with compressed air. Pumping up your "tank" won't have the same expansion if any so you maybe good.

I'd use this project and a few potiential others (LCA mount skids and gas tank skid armour) as reasoning to get a small welder. I know what you said about your neighbors and memories of the fire but as long as you're cool you most likely won't be breaking any laws but making a few welds every now and then. Hell if it got really bad with the neighbors bring the wleder inside and weld in the kitchen :wrenchin:. My little POS, HF, 90amp flux core welder has more than paid for it's self and lasted longer than I hoped for. I'd like a better welder with more power but for $89 mine was hard to beat. No gas, 110v and small. It's done what I've asked of it and I'm satisfied.

[slomatt]

Here's a small update on this project. This weekend I discovered that the hole on the other side does not overlap the tube so I was able to drill it larger and tap it to 3/8 NPT. Currently I have a plug in the hole, but I can easily switch to a 3/8->1/4 NPT reducer if I want to use that port. The hole on the driver's side does overlap the tube so it was more complicated to seal. I ended up putting a modified t-nut into the hole and using it and some jb weld to weld a cover over the hole. The cover is bolted and welded in place so it shouldn't be going anywhere. This evening I hooked up an airline and pumped the bumper tank up to 100psi, it worked perfectly and the gauge didn't budge after 30 mins so it seems very well sealed. Pictures coming when I get around to taking them. :)

- Matt

[4x4mike]

Cool. I like the idea and have toyed around with th eidea of getting a factory receiver so I could do this. Since your port is on the other side are you going to flip it and cut the bumper?

[slomatt]

Mike, are you asking if I'm going to cut the bumper middle section out and flip it upside down to gain some clearance?

My plan is to modify the bumper as little as possible, to that end all I've done is sealed up the two holes and tapped a new 1/4" NPT hole for the air input. I'll probably also later tap another hole on the bottom above the hitch chain mounts (for protection) where I'll install a drain valve.

- matt

[slomatt]

Here are some pictures as promised.

Driver's side hole partially obstructed.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2847.jpg

Tapping the passenger's side hole to 3/8" NPT.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2851.jpg

Plugging the driver's side hole with a t-nut and a washer. The bolt and wire are only temporary.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2857.jpg

Passenger side with plug.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2858.jpg

Temporary rig for pressure testing.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2859.jpg

Parts for the "secret" next stage of the project.

http://www.blankwhitepage.com/gallery/albums/t4r_oba/IMG_2862.jpg

- Matt

[4x4mike]

Mike, are you asking if I'm going to cut the bumper middle section out and flip it upside down to gain some clearance?

My plan is to modify the bumper as little as possible, to that end all I've done is sealed up the two holes and tapped a new 1/4" NPT hole for the air input. I'll probably also later tap another hole on the bottom above the hitch chain mounts (for protection) where I'll install a drain valve.

- matt



Yep, a flip of the receiver and notch cut out of the black bumper. Sounds like that a no. I thought your "good" hole was on the passenger side not the drivers where your current hose comes out.

I think this mod will be a solid one and work well. And with a drain where you mentioned will be well protected even if you come down on a rock.

[strykersd]

Looks good! This got me thinking, I wonder if I could make my first generation 4runner's roll bar into an air tank...

[paddlenbike]

Nice work Matt. I am anxious to see what the electronics are for.

[slomatt]

Nice work Matt. I am anxious to see what the electronics are for.


Imagine that you have a small controller in your car where you can store several preset pressure settings and when you hit the "go" button it automatically inflates your tires to the selected pressure. You can walk away while it's running and have a beer. I'm working on the proof of concept at this point and as of yesterday all the parts have arrived. It's also technically possible for it to deflate your tires to a particular setting, but I'm happy with my Stauns and would rather not have to hook up hoses to all 4 tires to deflate.

- Matt

[4x4mike]

Similar to what I was thinking. I thought the 2 little sensors would control pressure into the tires (front and rear), like pressure switches. That's cool if you can get them to deflate as well. I like the idea of having an OBA system capable to reaching a high pressure but also have a secondary "setting" that would cut off air (input) at a certain pressure. I've tried it before with a regulator but it didn't work as I wanted.

[L33T35T Tacoma]

Another way of having preset pressures would have multiple pressure regulatos pre-set, and use a series of T-fittings and electronic air solenoids. A little more mechanical than electronic, but effective.

[slomatt]

Similar to what I was thinking. I thought the 2 little sensors would control pressure into the tires (front and rear), like pressure switches. That's cool if you can get them to deflate as well. I like the idea of having an OBA system capable to reaching a high pressure but also have a secondary "setting" that would cut off air (input) at a certain pressure. I've tried it before with a regulator but it didn't work as I wanted.


Mike, a friend of mine has a setup using a regulator and it works but it's just slow. I think the problem is that as the tire pressure approaches the regulator pressure the air flow into the tire gets really slow since the pressure differential is so small. My goal is to always be pushing high pressure into the tire so it fills quickly and then stop it when the target pressure is reached. The difficult part is that the pressure you read while filling the tire is inaccurate so you have to cycle the valve off and let things stabilize to get an accurate reading. I'll also have a "full pressure" mode where the system is wide open.

- Matt