Gas Engine for Vac Pump

[Dennis H.]

Ok I need to find a gas engine for one of my vac pumps.

I am looking at replacing the 1.5HP electric motor on my surge alamo with a gas engine. If I remember correct you have to double that for gas. So I should be looking for a 3HP gas engine. Is this correct?

My question is how do you find a 3 HP engine when they now show the torque rating instead? I know there was a lawsuit out against the engine manuf's about over rating the HP of the enigine so all of a sudden they no longer show HP just the torque rating. So how much "Torque" will I need for a 1.5HP electric motor replacement? Or should I be looking at certain size engine, cc's?

Next question, how much gas can I expect one of these enigines use in a 24 hour period?? I know I will have to add a larger fuel tank right?

[mountainvan]

I have 5.5 horse honda on my 4 pumps. run 8 hrs on a tank of gas and has plenty of power.

[brookledge]

I had heard that it is 2.5 times for electric to gas
So 1.5X2.5=3.75 Round it up to 4Hp gas
I hadn't heard that you can't by engines by HP ratings. That must suck trying to know if an engine will be strong enough. I'm sure there is a torque rating guide some where. Do a search on it
Keith

[tuckermtn]

Dennis- when I needed to get a gas motor for my surge, I bought a job site air compressor with a 5.5 hp honda motor on it- paid less than $300 and I just switched it over for sugaring season. like a two for one deal...I use it the rest of the year for blowing out the air filter and radiator on my feller-buncher.

worked on the surge bb4 I had it on last season- but this season it will be on the sp-11.

[Haynes Forest Products]

Go on Ebay and play the game. Dont assume that because its red that is a Honda. Bigger isnt always better........unless were talking about my wife;) Having a 7 HP at high idle is as good as a 5 HP ripping and roaring.

Did you know that you can get a lawn mower for free that is a vertical drive and keep it that way and let the belt do a 90 degree twist and all is well:)

[maplemat1]

i have a 5.5 honda on my surge alamo and with the pulleys i only run the engine at about 3/4 throttle to get the 1800 rpm that is the max for that pump

[lpakiz]

I run a SP-11 with a 3 HP motor, which originally had a 3/4 HP electric. I got it off of an old snowblower. (Garden tillers had these also) If your system is leakfree (see Haynes) you won't need much RPM. That is an advantage of gas over an electric motor--You run only as fast as you need to to maintain the vac you want. I can't remember if it ran an hour on 1 1/2 quarts of gas or was it a quart of gas ran it for 1 1/2 hours. I did run it hardly off of idle and it never did foul up or give any other kind of trouble.
Good Luck!!

[Dennis H.]

Thanks for the info, it looks that I will be looking for a 4-5 HP Honda. I did find that on Northern Tools website they had data sheets for the honda's and they show the horsepower and torque curves. So I will look there for the model and size of engine and then look around for the best price.

Now I got to figure out what size pulley I will need for the engine.
If memory serves me correct the alamo likes to run somewhere around 850 rpm's right?

So with the 10" drive pulley on the vac head and the engine running lets say 2500 rpm's I would need a drive pulley for the gas engine that is close to 3.4"

If I am off on the vac rpm let me know. I am going off what I remember and also the rpm's and pulley sizes that are on it right now.

[jasonl6]

I've been looking at a gas engine for one of my remote sections too. The pump didn't have any motor when i got it so i can either put on a gas or an eletric and run a generator.

In my quest to locate a good cheap motor my neighbor suggested one from northern tool http://www.northerntool.com/shop/tools/product_200377914_200377914 They are around $180.00 and he has used them for a few years to power the log spliters he uses. They start every time on the 2nd pull and 80% of the time on the first. You can use a used motor but when it's 20-30 degrees i don't want to be messing around with a used motor wondering why it won't start.

I am considering this motor from heighbor freight http://www.harborfreight.com/engines-generators/gas-engines/65-hp-horizontal-shaft-overhead-valve-gas-engine-66015.html It's 6.5 hp and when i looked this morning it's on sale for $100. I also found a coupon in a magazine this week for harbor freight that gives me 20% off an purchase even on sale items. $80 looks pretty good to me :-)

Jason

[Dennis H.]

I wonder how reliable that one from Harbor Freight really is? It would be a throw away item if you start to have problems.

I saw the Northern Tool ones while I was looking at the Hondas, I see they have a 2 year warranty so I wonder if they are good.

It is kind of hard to not look at them when you are looking at paying almost $400 for a Honda and they run only 1/2 the price

[mountainvan]

reliability is big for me, that is why I use honda. I have 2.5" pulleys on my gas engines. just above idle and I can pull 20-26" all day long. I am going to get boat gas tanks to hook to the engines this year so they can run for a couple days straight.

[jasonl6]

one of the local amish familys use the harbor freight engines and they said in 2 years all they have done is regualr maintence. Of course with cheaper stuff the quality could be hit or miss. For $80 i'm gonna try it. It has i think a 30 or 60 day waranty. I'll bring it home and start it, run a couple tanks and see how it preforms. I only need a 3-4 hp on my sp-11 so i figure i'll be in the clear with a chinese rated 6.5 at a little above idle.

Plans to get on later this week if i do i'll post on how it is.

Jason

[Haynes Forest Products]

I got one of the Honda knock offs and they work ok till the things start to rattle apart. Case bolts falling out and carb screws coming loose.

[jasonl6]

I picked up the motor yesterday. It was an in-store special at $130.00 i told them of the internet price and they told me I needed to print it off and bring the page in to recieve the internet price. After I explained that I had drove over two hours to get to there store :mad: they check the internet themselves and gave me the price. Since they price matched the internet I couldn't use my 20% off coupon :( . I ended up paying around 109.00 with ny state tax. Gonna mount it to the sp-11 today and give it a test run. Will post pics/review later.

Jason

[Dennis H.]

I picked up one this morning also from Harbor Freight.

Put oil in it, 1/2 quart. and some gas, 3rd pull and it was running. I want to mount it to something and let it run for awhile.

Nice little engine, I think well worth $100. Now I have to pull the pulley off the electric motor and try it running the vac.

Jason6 I am glad that you mentioned them. I would love to have bought a nice honda, and I may still, I just have a limited amount $$ to spend on this vac setup. We'll see how long this baby lasts 1st.

[jasonl6]

I had the same results with mine today. I had hoped to mount it to my sp-11 but decided to paint the pump and tank before i mounted it and it was a poor day for paint drying.

As for the motor i pulled it out of the box also put in 1/2quart of oil and fuel. On the rd pull she fired (might have sooner but i didn't look close at the choke picture ;) .

Will try and mount it tomorrow morning if the paints dry and giver her a good running.

Side note for those conserned. 60 day warranty and for $25 can be extended till 2 years. I didn't get it but for some it may be cheap insurance.

Jason

[jasonl6]

Worked on mounting the motor up today. I made a small plate out of some 1/8" plate steal and bolted that to the motor and sp-11. I fired her up on the first pull several times today. With the motor at idle with my hand over the intake pipe I was getting 25" hg. Once I get it hooked to the lines I am hoping for 20+ and I can always idle up if I have to.

So far I'm super happy with my motor. I have about $250 into the motor($110), sp-11($125) and 3" pulley ($11).

[Haynes Forest Products]

I would keep an eye on all the side cover bolts and carb. Looks good and its nice to start out new. I have one on my kids Gokart and it rattles loose every so often but it starts every year without fail.

[Dennis H.]

I just got a coupon in the mail yesterday for 20% of any purchase at Harbor Freight, Man I should go back and buy a second one just to have. They are really nice.

I need to now run to Tractor Supply to pick up a pulley for it.

Jason I am surprised that you were able to start it up with the pump engaged.
I can see how a vane pump wouldn't be a problem spinning while starting the gas engine but a piston pump I would thought be too much resistance to allow the engine to get up to speed to fire up.

nice setup though

[jasonl6]

Yep it pulls fine. Not sure how one would make a setup for it to disengage unless a centrificule (SP?) clutch was used. Waiting to see how she pulls and runs at 20f on a cold march morning.

Jason

[3rdgen.maple]

Loctite Haynes Loctite.

[Dennis H.]

I am going to go see a setup this coming weekend, but if I had to build one myself on my own I would have an idler/tensioning pulley in there that is on some sort of lever that you would use to engage the idler pulley to the belt. It would take just enought tension off the belt so it would slip until the engine is up to speed.

With my sp22 it has a 1 1/2 HP electric on it and in the mornings when I turn it on it will trip the breaker once or twice till it gets things going. Right now I can go out there and it will fire right up no problems. The oil tends to get a little thick when it is hovering around freezing.

Just something to think about.

[DrTimPerkins]

With my sp22 it has a 1 1/2 HP electric on it and in the mornings when I turn it on it will trip the breaker once or twice till it gets things going. Right now I can go out there and it will fire right up no problems. The oil tends to get a little thick when it is hovering around freezing.

Our oil-flood pump would do that too. We just put two good-sized reflector bulbs hanging close by pointing right at the pump. When we turned the pump off after things had completely frozen up, we'd turn the lights on. Kept the oil just warm enough to start-up smoothly. Once the pump was on and running, the lights were turned off.

We're just finishing switching out our two flood systems this year for two Busch Rotary Vane "Claw" pumps. No more oil or cooling water to worry about...we'll see how it goes. Got our fingers crossed.

[Bucket Head]

Hello Dr. Tim. I know very little about vacuum pumps, so your "no water or oil cooling" statement got me wondering. Do these pumps generate less heat than the others? Or are these pumps air cooled like an air compressor pump or small gasoline engine? Do they have cooling fins on them?

Thanks,
Steve

[tuckermtn]

a few things I learned about gas motors for vac. pumps last spring-

1. don't skimp and buy the cheap "white" metal pulleys from tractor supply- get a good cast iron one-

2. buy several spare keyway pieces- use silicone or some other type of binder/sealer (perhaps loctite or RTV?) to coat the keyway- then let it set up- absorbes some of the vibration caused by the motor

3. you can start a BB-4 or other large vacuum pump under load if you have vacuum regulator near by- just open it way up to get the pump started and then twist it down to where you want it once the pump is going.

just my $.02 worth- but Parker gets most of the credit for the solutions...

[Haynes Forest Products]

I go along with Tucker when it come to GOOD pullys. The best ones are a hub and sheave set up that is a keyed hub with a taper that the sheave tightens to. They dont slip or vibrate off because the hub gets clamped to the shaft. NOTHING is more agrivating then trying to keep a pully tight on a shaft. Plus the HP rating is higher on the better pullys so the belts last longer. I have a tightner on mine and I use a double pully with the idlers set up that makes cold starts easy.

[DrTimPerkins]

I know very little about vacuum pumps, so your "no water or oil cooling" statement got me wondering. Do these pumps generate less heat than the others? Or are these pumps air cooled like an air compressor pump or small gasoline engine? Do they have cooling fins on them?

Specs and info are at http://tinyurl.com/39zopvw

They are forced-air cooled. Whole thing is encased in a metal shell, so hard to tell what it looks like inside. They are very high tolerance, but with no contact between the rotors, so less heat generated (supposedly). These types of pumps are often used in science and industry for reliable high-vacuum (or compressor) applications.

Advantages: Compact. Low maintenance. No oil or water. Very high Hg and great CFM at high Hg. Can run on a VFD (less wear and more energy efficient).

Disadvantages: Cost (quite pricey little buggers) and you don't EVER want to pull liquid though them. They come with a special type of moisture trap to remove moisture in the air stream and to (hopefully) prevent liquid from moving through the pump. If you pull water through it or it breaks for some other reason (unlikely if it's running 6 wks per year)....you're probably not going to be capable of fixing it yourself. This is not your standard dairy pump gents.

Lapierre and Bascom's sell these (we got ours through Bascom). Both of our two bush areas will have identical pump systems (finally). Ours are the model 1142.

We've had a collection of different pumps over the years, but like to try new things. Not a lot of them out there in the woods yet that I know of though. Hope to have good things to say about them after next season.

[Bucket Head]

Thanks for the pump info Tim. Good luck with them and I hope you have good results to share with us also!

Steve

[tuckermtn]

not sure if anyone else on here has dealt with www.smallenginewarehouse.com but I have been impressed so far. tons of motors- some without gas tanks, so you can add a bigger one.

just bought a new robin/subaru 4.5 hp gas motor for one of my sp-11's. $210 and 20 for shipping. have a decent reputation from what I can tell. more expensive than the chinese ones but cheaper than the hondas. We will see how it holds up...