It's been almost 9 years when I started collecting parts to build another belt drive generator. Some members might remember the first belt driven generator I've built in 2009. ( http://www.microcogen.info/index.php?topic=61.0 ) The thing was heavy, it weighed over 1200 Lbs, At the time I was barely able to role the thing out of the garage to run it. I threw my back out a number of times and I decided to get rid of it before I seriously injure myself. I than built a direct drive generator using a Kubota Z482 engine driving a Markon 3600 rpm generator head. ( http://www.microcogen.info/index.php?topic=1283.0 ) it was a very nice looking little unit and it worked ok, but, there were some things I did not like about it.
* It was not quiet.
* Engine seemed stressed out running at 3600 RPM's.
* The Markon generator head emitted a good amount of trash when loaded.
With these issues I decided to sell it and start another build. And the last one was a beauty. It used a Kubota D1005 3 cylinder diesel directly coupled to a Marathon 1800 RPM generator head. ( http://www.microcogen.info/index.php?topic=1743.0 ) The unit seemed to be low stressed. The power it produced was very clean and if needed, it could run hundreds of hours non stop.
The only concerns I had were:
* Parts were expensive.
* Most of the time it was too large for my needs. So a load bank was set up to load the generator to at least 50% load.
I felt it was a waste operating a load bank and I was thinking of switching to propane, so I sold Kubota D1005 powered generator to a member on this forum.
Years went by and being undecided on what power source I will be using on my next build I decided to wait.
Early this year I wound up purchasing a number of Yanmar clone diesel engines to sell and it turned out I kept 2 engines for this project. I decided to start one of the engines up. Well, it was LOUD. I realized that these engines will not meet noise restrictions for RV use. This is when I decided to try out a Honda GX390 gas engine and this is where this project starts.
The base is 6061-T6 aluminum channel, 12" wide and 1/2" thick at the web. The material cuts very well with a cross cut carbide blade on a table saw.
My understanding is that 6000 series aluminum is not easy to weld. And, the amount of welding required would generate enough heat to possibly warp the base. I don't want to take that risk. So, I decided to bolt the base together. Before I bolted the 3 inch angles to the channel the surfaces of both angle stock and channel that butt together when bolted were cleaned and than primed with LOCTITE 7649 primer. This gives the LOCTITE 680 retaining compound a good surface to adhere to and, helps speed up the curing process to under one hour. The retaining compound stops all sliding/movement that can happen from vibration. Been using it for years and it works. The fasteners used were 3/8-16 grade 8 bolts. LOCTITE 271 high strength thread locker was put on the bolts and installed than torqued to 25 ft-Lbs. The reason 271 Red LOCTITE is used is this part of the install is considered permanent and there will be no need to remove the angle stock from the channel.
Before mounting the engine and generator head, the base was checked for flatness. I brought the base to a friend that works at a metrology lab and he checked it and mentioned it was good the engine end was flat but generator end was off a couple thousandths. It was no big deal. I spoke to the application engineer at Meccalte U.S. headquarters and what they recommend is, loosen up the housing bolts and push the generator down on the base until all four feet are planted firmly with no gaps and then re-torque the housing bolts. Everything worked out well. Once the engine and generator head were mounted the pulleys were installed and checked for alignment. The alignment was so close I could not slide a sheet of printing paper between the pulleys and straight edge.
The idler tensioner bracket was cut with the table saw. Since I don't have a Bridgeport Milling Machine so, I had to use what I have. The Delta Uni-saw did a pretty good job. The ends are straight and square. I finished rounding the corners with the router and an 1/8" round over bit.
There will be two idler pulleys used. It took quite a while to find an idler that will adjust manually by rotating the pulleys. On my first test run I noticed that the belt still has some harmonics while running. The simple solution is to run another on the pull side. It does not need to flex the belt much. A quarter of an inch at most should be fine. The pulley just needs to put just enough pressure on the back side of the belt to deaden the harmonics.
The pulleys I'm using are 1995 Ford Taurus SHO timing belt tensioners. They are very wide and seem to work well.
Just finished mounting the idler for the belts pull side.
Unfortunately I will have to wait till Monday to test the setup. The idler pulley is cracked and splitting open so another one is on the way.
That unit is looking really good !.
Can't wait to see pictures of the finished product.
AND the youtube walk-around video of the unit running.
cheers
Thanks Veggie,
I'll work on a YouTube clip soon.
Thanks for your support. I appreciate it. Your input helped speed up the process for this project to happen much sooner than expected.
The belt tensioner replacement was supposed to be here Monday. DHL is great, it arrived three days early!
The pull side tensioner was installed and I had time to do a short test run. So far so good. Tomorrow is the day to stress the unit out.
I'll get the digital tach out and get true numbers unloaded and loaded close to 30 amps.
I'll be unlocking the topic this weekend. Probably after I post the most recent pictures.
Posted picture below is of the idler assembly while the unit is running.
Another important step are the fasteners used to mount the engine. The holes for the engine block, in the specifications read 11mm. Most people would accept 10mm fasteners and move on. When I drilled the base a jig was made and locked down on top of the base before drilling. It prevented any movement when drilling holes for the generator head and the engine. The fasteners used for the engine are 7/16-14 grade 5 bolts with smooth shoulders that slide through the base and most of the engine block. This reduces movement of the engine block. The 7/16 fasteners are slightly larger than 11mm (Decimal for 11mm converted to inches is .4331 & Decimal for 7/16 of an inch is .4375) and the fasteners slide in by hand. I guess my Craigslist $5.00 delta floor standing drill press might need an overhaul, or, the holes that Honda claims to be 11mm are actually machined to 7/16 of an inch? Hmmm... Anyways, the 7/16 of an inch bolts are a very snug fit and hopefully everything will stay aligned for a long time.
The fasteners used for mounting the generator head are 10 mm, 1.25 pitch, 8.8 grade.
Judging from the pulley diameters you are running the engine in the 2700 rpm range.
Is the noise level at that speed more or less in line with what you were expecting ?
From the calculations It's running in the 2570 to 2600 range. I'll have exact readings later today.
And the noise level is better than I expected. The genset definitely can be made to meet noise ordinance requirements for RV parks.
Veggie, with no load@ 62.67hz you were almost dead on! ---2711 rpm.
With a 31 amp load @ 60.49hz I got a reading of 2604 rpm.
I only need 30 Amps continuous. I just got done pulling over 55 Amp momentary surge and the good thing is frequency is not drooping below 59 Hertz at any time.
The engine needs some time to break in so more tests will be done soon.
Here are some pictures.
To prevent oil getting all over the base. The Base was filed below the drain plug.
A top view of the idler assembly.
The next step is to instal an electrical enclosure for the capacitor's and buss-bar where the generator will be wired. There will be a 30 amp RV breaker box that will tie into this enclosure.
I felt the test the other day was not as accurate as it should of been so I decided to do another.
The Makita heat gun used on the test was constantly switching on&off and in turn, true readings were impossible to record.
For this recent test the equipment used to load up the generator were:
2——1500 watt rated space heaters
1—— CFC vacuum pump.
1—— Delta sawdust/wood chip vacuum
With no load the readings read 129.4 volts at 63.79 hertz.
With a 31 amp load the readings read 116.7 volts at 59.79 hertz, engine speed was 2588 rpm.
(Readings were taken after an hour of continuous run time loaded at 31 amps.)
I feel the readings turned out to be more accurate on this test.
I met the goal of reaching 3600 watts continuous output with a good surge rating.
I'm curious on the fuel consumption on a 3600 watt load. More testing soon.
That's an interesting generator head. Have not seen one like that before.
What type is it again ?
The generator head is a Mecc alte SA20-130/2 APU generator head.
8.4 kVA - 3600 RPM
120/240 Volt, Single phase, 60 Hz.
There is not much info on these for the public. They were designed for specific OEM's such as Thermo-King, Carrier and a few others.
Here is some info:
https://www.meccalte.com/downloads/SA20.pdf
Thanks hwew,
It's a nice little compact gen head.
I would like to play with one of those pancake alternators like you had on your Kubota 2cyl.
Unfortunately they are very expensive and hard to find in Canada.
I had an idea of putting one on the shaft of my Lister. I think they make power at low speed, although greatly reduced power.
Did some testing on the generator this afternoon and I've been noticing a good amount of vibration resting my hand on the engine. At first I thought the 7" pulley was out of balance. But, when I increased or reduced the RPM's on the engine by a couple hundred RPM's higher or lower the vibration would reduce considerably. I took the pulley off and ran the engine again and nothing changed. This engine has all the classic symptoms of critical speed phenomenon at the speed I've chosen to run it. Honda also has a write-up about this In their tech manual and says to watch out for it at certain speeds and make adjustments as necessary. So, where does this leave me? The engine speed/output was enough to meet my needs where it was set. So, I will have to go up in RPM's. I'll be setting it up to run it at 2950-3050 RPM's and than test it again.
Henry
How are the noise levels on the Honda GX?
Are they acceptable for your application?
It's been a while, just got done setting up the genset to run at around 3000 rpm's. The belt will be in tomorrow.
Veggie, the noise levels are ok. They will be better when the enclosure is made.
I hope I'm able to do test runs tomorrow.
Ran tests of the genset. Here are the results. With a 1200 watt load running at 3060 rpm the engine stalled. It just burned through over a gallon of fuel in just over an hour. ::) Sitting here puzzled how this could happen? Bob G suggested to measure 32 oz. of gas and and do another test run with the belt off the engine. Well, it ran for 21-22 minutes with no load.
It did not use this much before when running around 2700 rpm.
Here are the fuel consumption specs. under rated load. Honda GX390 uses .977 gal/hr @3600 rpm with an approximate run time of 1.8 hrs. per tank.
Today we think we solved the mystery. The engine had a bad vibration problem from 2600 - 2800 rpm. So this was the reason I changed pulleys to run it near 3000 rpm's. We think the vibration frequency near 3000 rpm caused the float needle valve not to seat properly and in turn gas more gas was being drawn in the carburetor and in turn caused a rich run condition. The spark arrester screen was covered in heavy soot. This GX390 had such bad vibration that when putting a hand on while running it the vibration hurt and causing some numbness.
What is going on with this project.
I brought the engine back and got a complete refund.
I purchased a GX240 and will be mounting it in the morning and continue testing again.
Will start over by running it at 2700 rpm and see how it does. Than run another test at 3000 rpm.
If the vibration is considerably less I will continue with the build. If the vibration is the same as before. I might have to change the design.
The reason I decided to try the GX240 is less rotating mass.
*Smaller, lighter piston
*Shorter, lighter connecting rod
*Lighter crank with shorter stroke
*Slightly higher compression
Hopefully the lighter rotating mass might reduce the vibration considerably.
More later.
Hooked up the GX240 and test ran it.
The results are as follows:
Ran much smoother but the engine surges bad. Did tests by heating it up good and no change. Next test was recommended by our fearless leader. Started the engine and closed the choke slowly to see it it stops the surging. Well, it worked!
I went on the internet and found the the Honda GX240 has surging issues. It is the way the carb is set up in the idle circuit. And this is non adjustable. I can't blame Honda. I blame our EPA. Do they understand that an engine that constantly surges will use more fuel than one that operates properly with the correct fuel mixture. All engine manufacturers are going through the same issues. The only way I see getting around this is pull the carb off, throw it out and install an after market fuel injection system.
But I'm at the point that I'm ready to abandon the gas engine.
Back to the drawing board.
So, I returned the engine.
PS, I just thought of something. What would of worked is rip the carb off, throw it out and replace it with a good Marvel-Schebler VH-12 carb from the 40's & 50's. But that modification would void the warranty.
Added:
Here is the carb I used on a Bolens 800 garden tractor with a Wisconsin S7D engine.
https://partmartusa.com/products/vh-12-carburetor-vh12-marvel-schebler-wisconsin-new-old-stock
Quote from: Henry W on January 26, 2021, 07:26:11 PM
Hooked up the GX240 and test ran it.
The results are as follows:
Ran much smoother but the engine surges bad. Did tests by heating it up good and no change. Next test was recommended by our fearless leader. Started the engine and closed the choke slowly to see it it stops the surging. Well, it worked!
I went on the internet and found the the Honda GX240 has surging issues. It is the way the carb is set up in the idle circuit. And this is non adjustable. I can't blame Honda. I blame our EPA. Do they understand that an engine that constantly surges will use more fuel than one that operates properly with the correct fuel mixture. All engine manufacturers are going through the same issues. The only way I see getting around this is pull the carb off, throw it out and install an after market fuel injection system.
But I'm at the point that I'm ready to abandon the gas engine and look for a good diesel.
Back to the drawing board.
So, I returned the engine.
PS, I just thought of something. What would of worked is rip that piece of §#¥% carb off, throw it out and replace it with a good Marvel-Schebler carb from the 40's & 50's. They are some of the best carbs period. I've seen how one worked. But that modification would void the warranty.
Added:
Here is the carb I used.
https://partmartusa.com/products/vh-12-carburetor-vh12-marvel-schebler-wisconsin-new-old-stock
Another option is to drill the jet to richen it up a bit.
I thought of it.... People say the idle circuit is non adjustable and you can't get to the holes to richen it up. The engine is gone. I returned it. I'm going to take some time and think about it. I would like to have the flexibility of adjusting the fuel mixture without taking the carb apart. And as we all know that ability has been taken away from us. So, when an RVer camps out 8000 feet in elevation the carb has to be taken apart and rejetted. And than do it over again once down to 3000 or below. How stupid is that? If someone wants an engine to run right at different elevations the carb should be adjustable on the fly. Spare the time of having to take it apart all the time. The EPA should of allowed RV generators to be exempt from this issue.
Henry
check your email in re to the air cooled diesel engine
bob g
Dr. G, your a genius!!!
You solved the problem!
I know what I'll be doing now.
Skunk Works is back in business!!!
i am flattered, however i am no genius
just a poor boy that has had to live outside the box in order to afford to get done what i want done.
i wouldn't have a clue what it would be like to simply put down a pile of cash for a ready made solution to a problem.
:)
It's time to take everything that was learned from the last 12 years and put it all together.
Going to rework a design that is 11 years old. When something works why re-invent the wheel.
This build is officially over.