Welcome to our newest forum

[Matt]

I have set this forum up as a place for me and the rest of GBO to share information about DIY projects.

Myself I almost never pay someone to do something for me that I can or think I can do myself except for oil changes 

I also hate to buy anything that works... I would rather buy it broke and fix it so I pay much less for it. I guess having just enough money to get by prompts one to save every chance they get or at least it does me. Plus I just like the satisfaction of doing it myself rather than paying to get it done. I like to think of myself as a jack of all trades who has even managed to master a few. In my chosen profession I am able to accumulate lots of "stuff" in which I can later use to fix the other "stuff" I have. This also leads me to experiment and create things just to see if I can. One of my current projects it s 3 axis CNC mill to etch my own circuit boards for my many other projects. I just completed a AVR/IPS programmer so now I can add micro-controllers to my projects such as the Charge Controllers.

With my CNC project I am getting real familiar with stepper motors and controllers which I can later use for robotics projects and such.

So anyone got any DIY projects they are working on that they want to share with the rest of us? Or maybe you want to do a project but have no idea where to start... ask away I will do my best to find you a tutorial or if I know how I will write you one... I am sure others here are as if not more knowledgeable than me and I hope they will chime in as well.

Matt

[Cornbelt]

I'm thinking of an air compressor that would put out a lot of volume (for a booth blaster). I can't help but thinking that a V-8 engine would put out enough CFM's to make it work, but still be a lot cheaper than the genuine article. Passed up a chance for  one at a swap-meet the other day, but they'll have another in April, so maybe by then I'll know whether or not its feasable. My idea is to disconnect the exhaust rockers and discharge through check-valves in the spark plug holes. Hopefully the 5-7 HP motor I've got will drive it fast enough even if I have to step it down to a lower RPM. Any ideas on how to figure needed horse power?

[Matt]

Can I ask what a "booth blaster" is and does?

I believe I would take the intake pushrods out and put in real weak springs on the intake valves and just let the vacuum open the valves as the piston goes down each time. Otherwise if you let the cam open the intake valves they will only open every other revolution of the crank shaft and you'll be wasting fuel. In a 8 cylinder engine with weak springs on the intake valves you would have two cylinders pumping air at the same time so actually you'll have a 3 cylinder compressor.

I assume this will be tank less so I think that a 7hp might do the job but a 10hp would for sure and run the water pump as well. I think with a 7 you will need to figure a different method of pumping the coolant like an electric motor. Or you could pull the head off your 7hp and replace the head gasket with some high temp copper RTV which will give it a little extra kick. You may need to redo the RTV after about 3 to 4 hundred hours of use though.

I would think that a 2:1 or 3:1 ratio would give you more than enough CFM at around 90-120psi depending on the shape the motor is in to start with and how much piping down you do from the motor to the nozzle.


*EDIT: I would also use a 200-250psi pop off on each cyclinder as well just for safty sake after all if you were to get a clog in the output side it could get real nasty real quick...

Matt

[mirage1988]

Or if you could figure out a way to block off the fuel and spark to one bank of cylinders you could use one side to run the compressor on the other side. The hardest part would be modifying the intake manifold so you get air but not fuel.

After thinking about it a bit more, I would put all three ideas together. Take out the intake pushrod and lifter from one side so the intake valves stay closed, put a weak spring on the exhaust side so the exhaust valve acts as a check valve, and install a check valve in the spark plug hole. Ground the plug wires on that side,and you have a self powered air compressor.

[Matt]

After thinking about it a bit more, I would put all three ideas together. Take out the intake pushrod and lifter from one side so the intake valves stay closed, put a weak spring on the exhaust side so the exhaust valve acts as a check valve, and install a check valve in the spark plug hole. Ground the plug wires on that side,and you have a self powered air compressor.

You can buy a kit to convert most v6 and v8 motors or a VW air cooled kit. It is a 4 stage compressor head and a cam. I have the site book marked but can’t think of it right off the top of my head.

The only problem that I see using the exhaust as the intake it that unless you have the heads reworked there is a better chance of getting carbon in the cylinder and a clog later down the line somewhere. Also it would be much easier to filter the air if coming from the intake.

Matt

[45-70.gov]

i once had an air compressor on the job  to run  a ram  hoe

it was  an  inline  6 cylender

3  had spark plugs
3 had an airline

i  bet a  v8  might be better

intake manifold for  one side  only thing tricky

exhaust  one side ...compressed  air on the other

cam  and valves  need  no modification

[Matt]

i once had an air compressor on the job  to run  a ram  hoe

it was  an  inline  6 cylender

3  had spark plugs
3 had an airline

i  bet a  v8  might be better

intake manifold for  one side  only thing tricky

exhaust  one side ...compressed  air on the other

cam  and valves  need  no modification

Although it might work you will still only be getting air compressed on every other stroke. This will cause it to be much less efficient. Also the exhaust ports I think would be best left closed and air pumped out plug holes to reduce stepping down the piping and increasing potential failure areas... jmo though

Matt

[Cornbelt]

I like the idea of a weak spring on the intake. Have a Cushman Cub with that design. Another question is cooling; how hot will it get without combustion going on? I'm thinking that the radiator could be a whole lot smaller. Also the water pump could have half the wings on the impeller pruned (people used to do that to both pumps on flathead V8 hotrods).  If it makes a difference, the  5-7 hp motor is electric.

[Matt]

Another question is cooling; how hot will it get without combustion going on? I'm thinking that the radiator could be a whole lot smaller. Also the water pump could have half the wings on the impeller pruned (people used to do that to both pumps on flathead V8 hotrods).  If it makes a difference, the  5-7 hp motor is electric.

I agree the cooling system can be hacked up. You should need no more than a few gallons of water to keep it cool.

What is the rated RPM of the electric motor?

You may have to change the ratio to more like 8:1 or 10:1 if it is a high rpm motor (over 4000rpm)

The v8 will need to run at no less than 750rpm for the oil pump to work properly and you should also use thin or light weight oil seeing as there will not be anywhere near the heat that the engine is designed for so thicker oil will strain the electric motor.

I would think that the best speed for the v8 would be around 1500rpm max.

 I cannot stress enough that you will need pop off & check valves on each cylinder to prevent an explosion.

Matt

[45-70.gov]

solid plate blocking intake on one side
all push rods removed  so valves stay shut  on same side [air side]
check valve at each exhaust port to  only allow air  in
check vallve at each spark plug hole  to  only allow compressed air out
then they can be plumbed to the tank

that would  compress 4 times per revelution
hallf  of  350 cubic inches    is   175 cubic inches   per revelution
and 4 thousand rpms  is  700 thousand cubic inches per  minute  of  air volume

700 thousand divided by  46,656  =  cubic yards per minute
[don't have my calculator  and that ine is too big to do in my head]



might want a smaller  carberator

[Cornbelt]

Electric motor RPM is 3450. If using all 8 for compression, speed of V8 could be reduced to considerably lighten the load on the electric motor and still give me 500 CFM's, which is what I'm shooting for.  .45-70, according to your math, I could spin it half as fast and still get 450 CFM's. I could live with that.  Weak intake springs could also be used as a compression release with a handle to cam them open till the thing gets up to speed, (a la Cushman).

[mirage1988]

Using an electric motor to turn a big v-8 seems like a good idea, but it is like using a sledgehammer for a fly-swatter when you think about it. A gas motor is built to withstand 12,000 psi or more combustion pressure. To turn the crankshaft alone would use up most of your 7 horses, much less the rods and pistons. Don't mean to rain on your parade, but I am not sure it would pump much air.

[45-70.gov]

i  think  the main purpose  is to eliminate power dependency

[Cornbelt]

Ideally, an air screw would be the ticket, but they have a pretty stiff price, and you don't see many used ones lying around. As far as pressure goes, I wouldn't be needing nearly as much as a typical compressor puts out; just a lot of volume which would reduce the resistance against the electric motor. Pressure wouldn't need to be more than 75 lbs.

[45-70.gov]

i  do small jobs  mostly

just  use my scuba tank [3 thousand psi stepped down  to a hundred] 

to run my nail guns....blow dirt inflate stuff   ect......stays in truck  on a backpack

i  helped install  the compressor at the dive  shop

so refills are free.........last tank  lasted  all summer

[mechanic]

Compressor companies once routinely did what you are talking about for portable compressors.  I once rebuilt a 302 Ford engine that ran on 4 cyls. and compressed with 4.  The intake valves were left intact, and the exhaust pushrods were not present.  The spark plug holes had a spring loaded one way valve screwed in.  It put out enough air to run a very large sandblaster.  It was on a fixed stand with a standard auto radiator for cooling, and the whole shebang was mounted on a trailer.

You might look around some old equipment lots and luck up on one that could be refurbished.....