Designing for long hours of off grid use.


Bottom Side of Gen Sub Frame

Bottom Side of Gen Sub Frame

A lot of things work for backup, but lots of running hours cause us to pay closer atttention to our designs. I’ve been studying a generator that was in the field for 10 years, and ran as much as 12 hours a day. The weakest part of the design was the generator mount, it ran a lot of years before a part broke on the sub frame, but it did break, and Murphy will assure it breaks at the worst possible time.  It caused me to ask.. how would I do it differently in the future?



There’s a list of things I like to consider in  DIYer design, but being able to remove a sub assembly quickly and take it to a work bench, or better place to work on it is a high priority in my designs. If we meet this goal, we also make it easy to remove a part to gain access to what’s behind it or under it. I placed the locking bolts on the right because the generator sets flush on the other end, and here on top and to the right, they are easy to see, and quickly locked or unlocked with a racheting box end and a single hand, the other hand sets the belt tension.  

In addition,  I try and avoid designs that others will have a hard time duplicating.. like long sloted holes for adjustments. Not everyone has the equipment to make them. 

A generator sub frame should be firmly mounted to the frame, as movement can cause bad things to happen over 40,000 or more hours.

So here’s a latest attempt to make it quick and easy and still clamp the head in place tight and secure.  The video was shot on my cell phone,  Hopefully you’ll get the idea, and maybe even better my starting place.   Don’t let that generator vibrate on the rails, it’ll cause a problem sooner or later.

As we develop our ideas, it is nice to avoid rountine tasks that take three or more hands.   Let me offer you an example of another thing you might see.  On this LisGen-6/1, the oil drain plug and the large access door are at one end of the machine, and easily accessed.  A pan easily catches an oil drain, and the big door is right there and un-obstructed to do any kind of work you need do. I’ve seen a few DIY Gen Sets constructed where the generator sat on that end, and made far more difficult the access.



We are DIYers, and few of us are professionals in design, but I doubt we’ll be able to top some of the blunders made by pro designers.  Some recent example given by DIYers? 2007 Toyota Prius Head Light bulb replacement.  A most expensive and time consuming task.   Others? How about the Chevy Monza, where the engine had to be jacked off it’s motor mounts to change a spark plug?  We DIYers can do far more thoughtful work. 

A caption for the above picture?  “Oil change time! I brought my friend along, we’re just gonna set this 230 pound gen head aside and put a pan under the drain plug”.   

Just one more bit of advice, I’ve seen some thoughtful builds, and on the final install, that important access door was wedged up tight against a corner in the gen shed.  I am a believer that Murphy takes note, and visits early to teach us that we need install a machine designed to be rebuilt in place in a place where we can rebuild it in place 🙂

Murphy seems to teach us more lessons over a life time than any other Teacher.  

Tools required to make this Subframe mount? A composite cut off saw, (cheap at Harbor Freight).  A drill motor and drill bits, and a welder.    


This entry was posted in DIYer Generator, DIYer Skills, Off Grid Power, Slow Speed Engines, Small Diesels and tagged , , . Bookmark the permalink.

9 Responses to Designing for long hours of off grid use.

  1. Nate says:

    long slotted holes, drill both ends and use a cut wheel ;). This article has given me some other ideas, hmm.

  2. George B. says:

    Nate, thanks for your comment..

    After looking over some of your recent work, I’m not sure you qualify as an amateur builder.

    Regarding the cutting of long slots, I’ve tried a number of things…. drilled holes at the ends and used the plasma cutter…. following a straight edge guide for one. But nothing seems easier than avoiding the need for slotted holes 🙂

  3. Nate says:

    I think im abandoning the slotted holes. They are not in the correct location, guess that happens when you don’t double check the model. I think i’m going to use a piece of flat bar on either side of the generator base so it can slide forward and back and hold it square to the flywheel. Use a front stop to limit forward motion, maybe another flat bar ontop to overlap the generator mount and something to hold it from moving back. I have to raise up the generator about a half inch to line up correctly so i dont know if i should just space it or make a new bracket but slightly lower so i can shim to fit. Open to ideas haha.

  4. George B. says:

    Do note the trick Soon Wah Lee taught me, a gift from his Father. You need design your mount where it can be ‘knocked’ into alighnment and then welded. Use shouldered bolts an never need align again. No shims required..

  5. nate says:

    not sure if i follow. If I use 4 studs in the correct location with a nut on each stud under the mounting place to align the alternator then jam it with a nut from the top to lock it together?

    • George B. says:

      OK… we need note, you are asking about direct drive gen sets and two beairng gen heads.. so others can follow along..

      Here’s the lesson from Soon Wah Lee’s Father.. (for direct drive with couplers)

      After the end of the Japanese occupation, Lee’s father was 16 years old and got his first good job on a plantation and was assigned to drive a tractor nobody else wanted.. a ‘Diesel’. Over the years he became the expert on diesels on this big plantation, and later the fabricator of a lot of machines. He built a lot of pumps, generators sets and more. Fifty years or more of experience.

      Just picture this…. make a sub frame for your gen head.. the first part is two pieces of angle laid out on the main frame. Now another set of angles attached to the gen head and the holes and shoulder bolts are a tight fit. Yes, you may need to add cross ties, as you will be making the angles meet on each side so you can ‘C’ clamp them together.

      Set a little too high. Use a small hammer to knock it down slowly as you watch your dial gauge and level to get a perfect alignment at the coupler.

      A digital level can allow you to put it on the main frame, and then reset to zero, this makes it easier to match the main frame as it need not be on the level where you work.

      once you know you have good alignment with spider in place, tack weld the angles together at the four ends.

      Recheck alignment, once you are satisfied, you now weld the sub frame base to the main frame OR use a drill bit and shoulder bolt that match, and drill the four holes you need through sub frame base into main frame base.

      What you end up with is a gen set that doesn’t need shims, and you can unbolt the sub frame and re-attach it without the need to re-align.

      Couplers ‘eat’ spiders when the alignment is poor, shoulder bolts and good holes are a must. Keeping them tight is important. Some pro builders even use a thick precision washer that makes use of a longer bolt shoulder, and then these washers are welded to the angles. We can’t have a longer shoulder on the bolt than the material thickness, and material thickness assures a better alignment and we use a more common shoulder bolt length.

      I hope this ‘paints’ the picture. I could write pages, but do note, some people attempt to fix basic alighment problems with spiders way too hard, or the use of a metal spiders. This can and does cause other problems.

      The value of Mr. Lee’s practice can be seen in the mind’s eye when you change out that first spider……no need to catch a stack of shims, and remember where they go..


  6. Gary Harper says:

    This is a great website! I really like the black strip over the eyes, as if changing the oil was an illegal or immoral act. Very cool website.

  7. ray balcom says:

    Like to know typical problems encountered from off-gridders who pump water on a regular basis. We are on solar trackers but occasionally have to run a generator off daylight hours to keep our tanks full during hot summer days. In order to be more efficient we are switching to a lister clone from a welder generator.

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