Hot rod compressor

[Robbyrockett2]

Good for those, who can get a golf cart. But they don't need to even think about the compressors!

I've seen several of DIY ideas for gas powered comps:

straight connection without any pressure switch etc - pump and the engine work all the time, it's no good at all.

centrifugal clutch - seems good, but engine works continuously at the time pump stops (good). I don't know how to lower the engine's RPM here automatically when the tank is full . It's possible, but it seems it requires complicated solutions. I thought about this way of making gas powered one, but today saw that video with electric start engine. I'm impressed, need to think over it.

engine with electric start - I think it's the easiest solution. Both pump and engine stop, it's real good. Here life of the parts become longer and you don't need to burn your gas all the time For an easy start (it's very important for gas engine start, I think) we can use the same valve that's used in random comps (that drops down the pressure between the tank and the pump).

On the centrifugal clutch . You would just wire an electric solenoid to the pressure switch. It pulls the throttle when air is low, thus accelerating the motor and engaging the clutch
It releases the throttle when the air is full, thus disengaging the clutch and returning the engine to idle speed.
Works exactly like electric compressors, except the throttle is what is controlled and the motor either revs up or idles.
No need for timer circuits or decompression valves.

Yeah starting and stopping the motor is great for not burning gas, depending on how you use it. ( keep in mind a carbureted motor can idle 3-10 minutes on the amount of gas it wastes to start up)
I still like the idea, however, also keep in mind , how long will your starter last if it is used every 5 or ten minutes?
It's also easier on an engine to idle for 8 hours then to start and stop 25 times.

Which is better just depends on how you use the compressor


Here you can find old gas golf carts for $100 sometimes. The ones that operate like I was saying have very large starters with very large gear teeth and are designed to be used very frequently. But might be a better idea just to get a muffler for one. I don't know what a golf cart motor and starter weigh, The starters are sometimes as large as the motors.

 

[Vladimir]

On the centrifugal clutch . You would just wire an electric solenoid to the pressure switch. It pulls the throttle when air is low, thus accelerating the motor and engaging the clutch
It releases the throttle when the air is full, thus disengaging the clutch and returning the engine to idle speed.
Works exactly like electric compressors, except the throttle is what is controlled and the motor either revs up or idles.
No need for timer circuits or decompression valves.

Yeah starting and stopping the motor is great for not burning gas, depending on how you use it. ( keep in mind a carbureted motor can idle 3-10 minutes on the amount of gas it wastes to start up)
I still like the idea, however, also keep in mind , how long will your starter last if it is used every 5 or ten minutes?
It's also easier on an engine to idle for 8 hours then to start and stop 25 times.

Which is better just depends on how you use the compressor


Here you can find old gas golf carts for $100 sometimes. The ones that operate like I was saying have very large starters with very large gear teeth and are designed to be used very frequently. But might be a better idea just to get a muffler for one. I don't know what a golf cart motor and starter weigh, The starters are sometimes as large as the motors.

You're right. Solenoid and electric start depends on how one's going to use it. And frequent starts for cheap starters also means something.
Good thoughts you've given!

 

[Robbyrockett2]

I'm not bashing the Idea, please don't take it that way. Just kind of spitballing

 

[Robbyrockett2]

Heres another thought, you could combine the two. put a thermal switch to control the starter. So when you had it turned to the "on" position. It would crank the motor if either the pressure was low or the engine temp dropped below a certain point. The solenoid would only speed up the motor if the pressure was low. When it reached pressure the pressure switch would kill the spark after the solenoid throttled down the motor but only if the engine were warm.
This would be excellent for if the compressor was going to run infrequently.
The thermal switch would make sure the engine ran enough to stay warm while the solenoid controlled how much the engine ran the compressor head.
Sounds complicated but really would just be the solenoid setup with a thermal switch and a DPDT relay.

So youd flip the compressor on, it would start the motor and then throttle up, when it reached pressure it would throttle down but continue to run until it reached temperature. Then it would start and run occasionally just keeping itself warm. unless it needed to pump, which it would start and throttle up.

I can draw up the circuit sometime if you want

 

[Vladimir]

I'm not bashing the Idea, please don't take it that way. Just kind of spitballing

I take all you write as reasonable ideas.

Heres another thought, you could combine the two. put a thermal switch to control the starter. So when you had it turned to the "on" position. It would crank the motor if either the pressure was low or the engine temp dropped below a certain point. The solenoid would only speed up the motor if the pressure was low. When it reached pressure the pressure switch would kill the spark after the solenoid throttled down the motor but only if the engine were warm.
This would be excellent for if the compressor was going to run infrequently.
The thermal switch would make sure the engine ran enough to stay warm while the solenoid controlled how much the engine ran the compressor head.
Sounds complicated but really would just be the solenoid setup with a thermal switch and a DPDT relay.

So youd flip the compressor on, it would start the motor and then throttle up, when it reached pressure it would throttle down but continue to run until it reached temperature. Then it would start and run occasionally just keeping itself warm. unless it needed to pump, which it would start and throttle up.

I can draw up the circuit sometime if you want

It's complicated, I need to think over it.
Yeah, the circuit would be great!

You have more possibilities there to experiment with gas powered compressor. Used golf carts, used compressors (ready to use). I would never find any golf cart here for 100$. No matter how heavy it would be, I think it's great variant to think over, but not here. You can make compressor on car wheels if golf cart parts are too heavy.
Buying ready to use gas powered compressor here is not for me and local market is not for this expensive equipment, I was selling new diesel heater for half a price of new one for almost two years. No result! I haven't even seen these relatively small gas powered compressors (that we're talking about) sold here. Guys in need for such eqpt make their own.
If I'd really need one, I'd have to buy parts and to make my own. I have for some years bookmarked link to centrifugal cluth, a man produces it for gas powered compressors. Some people here can't have 3 phase electric supply, so gas powered for them is only the solution for good air supply.

 

[Robbyrockett2]

I take all you write as reasonable ideas.



It's complicated, I need to think over it.
Yeah, the circuit would be great!

You have more possibilities there to experiment with gas powered compressor. Used golf carts, used compressors (ready to use). I would never find any golf cart here for 100$. No matter how heavy it would be, I think it's great variant to think over, but not here. You can make compressor on car wheels if golf cart parts are too heavy.
Buying ready to use gas powered compressor here is not for me and local market is not for this expensive equipment, I was selling new diesel heater for half a price of new one for almost two years. No result! I haven't even seen these relatively small gas powered compressors (that we're talking about) sold here. Guys in need for such eqpt make their own.
If I'd really need one, I'd have to buy parts and to make my own. I have for some years bookmarked link to centrifugal cluth, a man produces it for gas powered compressors. Some people here can't have 3 phase electric supply, so gas powered for them is only the solution for good air supply.

Ok I'll draw something up later today. I'll do one like I was saying and then one that can eliminate the starter timer circuit. ( you can use a capacitor and small relay hooked in the charging circuit to simply cut out the starter once the engine is running)

 

[Robbyrockett2]

Ok I'll draw something up later today. I'll do one like I was saying and then one that can eliminate the starter timer circuit. ( you can use a capacitor and small relay hooked in the charging circuit to simply cut out the starter once the engine is running)

As I started to draw the circuit I realized the capacitor thing would not work because it's a float charge system and would default to on because of the battery voltage ( I was originally thinking of using a High pass filter from the charging system to power a relay that cut out the starter once it wwas producing solid dc voltage). Oh well. I thought of something better and simpler yet. I believe the Lifans you're talking about are the honda gx200 clones. Some come equipped with an oil pressure cutoff switch. If they dont then there is a port for one so its easily added if im not mistaken.
The oil pressure switch is normally closed. I showed all switches open in the diagram just so you could see them.
T= Thermal switch (easy to find for automotive cooling fans ,usually about 190 degree Fahrenheit) air cooled fins usually are well over 200 warm.
S= Starter
OPS=oil pressure switch
That little guy in the bottom left is the solenoid for the throttle
To the right is the pressure switch
The two boxes above it are standard 5 pin automotive relays, I took a closeup so you could see the pin numbers.
I actually reversed 87 and 87A from how they are normally shown, but it is electrically correct so that is the correct pins to use.
and of course there is a Manual on/off switch for the battery.

When you switch it on the normally closed OPS powers the relay, closing the switch that enables power to the starter through the pressure switch, Once the OPS opens (meaning the engine is running) the relay switches the power from the pressure switch to power the solenoid. That throttles up the motor until the pressure switch shuts off. Now at any time the temperaure switch is usually open which means the top relay is feeding power to pin 30 on the other relay so if the OPS is closed (engine off) it can start the motor unless the temperature is over 190 degrees, then that relay does nothing.
I hope me changing the pin locations on the relays isnt confusing but just remember 87a is the pin the switch rests on when the relay is not powered.
The OPS is closed until the engine has oil pressure. The temp switch is open until its up to temp.

It's actually an extremely simple circuit, but I made a lot happen using it. So its a bit like chasing your tail trying to see how it works.
Im actually kinda proud of it..... Id call it elegant to accomplish all that with two relays, a pressure switch and a thermal switch
All components you could pirate from an old car.
Would have been much easier to just design a circuit and make someone have to order special stuff like normally closed temperature switches that could handle the current involved.

 

[Robbyrockett2]

but I messed up, I have to change it to shut down when it reaches pressure. Hang on....

 

[Robbyrockett2]

Ill have to re-draw it tomorrow. I'm tired... see....like chasing your tail. I'l get it though. I'm just trying to make it as elegant as possible.

 

[Vladimir]

Ill have to re-draw it tomorrow. I'm tired... see....like chasing your tail. I'l get it though. I'm just trying to make it as elegant as possible.

Thanx for the efforts!
You know, after all you write and draw, I wonder why you've ever asked about "any thoughts"? You know so much, that you can make thing almost out of nothing
Waiting for new circuit!

 

[Robbyrockett2]

Thanx for the efforts!
You know, after all you write and draw, I wonder why you've ever asked about "any thoughts"? You know so much, that you can make thing almost out of nothing
Waiting for new circuit!

Thanks, but often times someone points something out I had not thought of.
Sometimes something very simple.
Once because we had no batteries I rigged up a little 120AC to 12vDC converter in order to power the radio. All the while forgetting that the reason we needed the batteries was because we had no power because of the snowstorm. So after all, I realized, where was I going to get 120AC

 

[Robbyrockett2]

This should do the trick, Icaught a couple of mistakes from the original, and included the actual starter relay.
There are easier ways to do it, but only with special order parts.
Still. not bad for four standard 5 pin automotive relays and a solenoid.
Starts, throttles up and down, starts and stops for warmup or for pressure build, all completely automatically as long as the manual switch is on.
The only downside is that two relays remain active when the whole thing is inactive. So you need enough battery reserve to not drain the battery by keeping that small relay active for however long the compressor will sit inactive. You could turn it off if you arent going to use it for a long time. otherwise you could hook it up to a battery charger and leave it switched on all day long.

 

[Robbyrockett2]

The inactive current draw would be about .33 amps so however long your battery can power that and still have juice to crank the motor is how long it can sit inactive.
A little motorcycle battery in good shape could only last an hour or two between starts. With a lawnmower or car battery lasting way longer.
Any battery sitting there with a .5 amp trickle charger would be fine indefinitely.
The setup would be great for a shop that only has household electric and no 220

It would be OK for portable, but for portable id probably just run the simple centrifugal with a solenoid and just let the motor run for as long as I was going to be using it.

I could draw you up that circuit in like 5 minutes if you decide to go that route

 

[Vladimir]

It would be OK for portable, but for portable id probably just run the simple centrifugal with a solenoid and just let the motor run for as long as I was going to be using it.

I could draw you up that circuit in like 5 minutes if you decide to go that route

Do that, please! It would be great to know all possible variants, to think them over and to decide which way to go.

 

[SiRoxx]

Nice work Robby. I admire that you follow your train of thought all the way through, even if it comes to a dead end, at least you know. This one has no dead end and keeps on truckin.

 

[Robbyrockett2]

Nice work Robby. I admire that you follow your train of thought all the way through, even if it comes to a dead end, at least you know. This one has no dead end and keeps on truckin.

It's been about ten years since I've had to draw relay based logic circuits. This one has an AND, XNOR plus a pair of XOR's in one relay if i am remembering correctly.LOL So this was kind of a challenge. I know electronics some but I am no whiz. These days Id usually just accomplish something like this with one of the smaller knockoff arduino boards and a few 5v relays. Same as I would do for simple animatronics. I don't get into the real complicated stuff.

Vladimir, you might want to check back with me or someone else when you get your specific motor if you go that first route. Some of that is based on assuming the OPS is set up the way that common ones are, but they can actually be normally open or normally closed. Once you have a specific one I can look at its wiring diagram and make sure the circuit is right. Plus be able to say which wires to cut and how to tie them into the circuit.

For option B, none of that is necessary
I think the Lifan you're talking about is already wired up with a key switch for the starter and all that. So this is actually as simple as it gets.
All the other wiring would be left alone and just setup how it is from the factory. You would just add this to control the throttle. As easy as a light bulb and switch.

 

[Vladimir]

Vladimir, you might want to check back with me or someone else when you get your specific motor if you go that first route. Some of that is based on assuming the OPS is set up the way that common ones are, but they can actually be normally open or normally closed. Once you have a specific one I can look at its wiring diagram and make sure the circuit is right. Plus be able to say which wires to cut and how to tie them into the circuit.

Thank you @Robbyrockett2! If I'm ready to build my own, I'll be back to you definitely. You've got that bright mind that's hard to meet on the way.
But I think, this will not happen for a year at last. I've got a lot to do, among that "a lot" 2 stage compressor (380V) is the first to be built for the studio air supply. So, gas powered will wait.

For option B, none of that is necessary
I think the Lifan you're talking about is already wired up with a key switch for the starter and all that. So this is actually as simple as it gets.
All the other wiring would be left alone and just setup how it is from the factory. You would just add this to control the throttle. As easy as a light bulb and switch.

Yes, that one I've mentioned has key switch.
I'm not sure what engine I'd buy. Definitely, I thought about Honda. I had power generator from the brand at work, we always took it with us during expeditions (where was no power supply) and there was no issue with it for many years. It worked like Swiss watch.

 

[Robbyrockett2]

2 stage compressor (380V) is the first to be built for the studio air supply. So, gas powered will wait.

I would think so