Honda GX390 120 Volt RV Generator

[Henry W]

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.

[Henry W]

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.

[Henry W]

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.

[Henry W]

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.

[Henry W]

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.

[Henry W]

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.

[veggie]

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

[Henry W]

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.

[Henry W]

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.

[veggie]

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 ?

[Henry W]

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.

[Henry W]

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.

[Henry W]

Here are some pictures.

[Henry W]

To prevent oil getting all over the base. The Base was filed below the drain plug.

[Henry W]

A top view of the idler assembly.