DIY Inverter Generator (Scratch Build)

Matt can you get a fan off a old generator to fit ?



Maybe but then we are hunting for parts and then more likely modifying them to make work. Im not sure its worth the effort. An 8 inch radiator cooling fan will put out more air and would be much simpler. We have well over $1200 bucks we are saving by DIY’ing this so I think we can spend a few bucks on a fan :slight_smile:


I wonder if the radiator fan could be run off of the 12v charging circuit?


Yup, there will be a battery as well. But it will be ran off a relay with the ground of the coil tied to the oil switch. The hot side of the relay coil will be ran to the on / off switch of the engine so its not live constantly. So when the generator is stopped or runs out of fuel or what ever the fan not run and drain the battery.


Fair enough , on my inverter generators the fans are all electric anyway so i guess its in keeping with what you are building .


Ok I got the plates cut out. Well so far its going together, I didnt really plan any of this just in my head and did the part design as I went. But the hold up for now are some 3 inch long 5/16 bolts that I need to secure the stator to the mount plate. Then the next step will be to insert it into the rotor so I can get a measurement between the two plates that will determine the depth of the housing.


Ok I built and installed the housing today. Ran into an issue with the run out on the original taper shaft adapter. So I ended up re making it, this time I trued it up in the lathe. Yeah, yeah, I knowm and I knew better lol.

At least two of the magnets are cracked in the rotor. Not sure if it came that way or if I somehow cracked them inserting and removing the stator the few times Ive done it. Those magnets have also acculated metal shavings from the shop. But anyways I think I have it centered and the plan worked. We will see when we fire it up and try to make some power with it :fire:


That’s very interesting that whoever imports and sells these DuroMax engines over there in the states manage to get imperials into the casings ,what about the other nuts and bolts that say hold the carb on ? they are normally 10mm have they changed those as well Matt ?
Starting to look like it will be making you power real soon .


The Predator engines also use fine thread SAE, at least the two I’ve bought were like that. Maybe it’s just a standard now for Chinese small engines destined for the USA.


Some Chinese engines i tinkered with seems to have both imperial and metric threads at the same engine block, pretty annoying.
Often covers and fan shrouds are mounted with imperial, and some stuff on the block is metric, anyone else noticed this?


Sure. Sure.
And I can even give you my understanding of why this has evolved.
It was in U.S.A. “America” that the 1930’s, and especially in the 1940’s, that small gasoline lawn mowers; walk behind garden tillers/tractors; snow blowers; generators; pumps and small equipment engines really took off. So the driven accessories; their mountings, and shaft specifications were standardized and assigned patterns. SAE numbered patterns.
In “American” inch dimentions.
Later off-shore of U.S.A. engine suppliers knew for the ‘American market’ they had to supply those parts of thier engines in “American” patterns.
The American seeming insatiable hunger for small affordable personal IC engines by purchased unit counts has been a market bigger then the whole rest of the world combined.

Goren I find the tools confusion to use on mixed spec small engines, not so bad.
More confusing and slowing down was a Japanese Mitsubishi engine in a USA all metric Chrysler-Dodge product. Chrysler-Dodge using all 10mm, 13mm, 15mm and even 17mm hex headed bolts and nuts.
Mitsubishi engines using 10mm, 12mm, 14mm and 16mm hex headed bolts and nuts.
Then the European and Japaneses switched uses to inset flush head Allen’s!!!
“Improved” later to triple square male and female.
American then robotic assembly 'improved" to male and female Torx. Then even that improved to an improved Torx like spline inset or male head. Toss-in also many switching to using 12 point bolts and nut heads. Not a triple square. Not a Torx. Not a spline drive. Yeah. Then having to add true spline drive male and female headed tools.
Just tell me you love all of theses, eh-yeah.
This all sells a lot of tools for sure. I’ve had to replace out worn and snapped off new-improved tools just using destroying the tools tips. Where as I’ve never actually worn out a good quality combination wrench.
Steve unruh


Yup I believe this is a grand fathered in “industry spec”. The rest of the engine has to be in metric to satify ISO standards. However bolt pattern specs that are industry standards dont apply to ISO. ISO is for manufacturing conformity and will be in metric.


Yes, it’s true.
Tool confusion is no trouble for me, as interested in “vintage” equipment, old American automobiles, and older European autos also used a lot of imperial threads, i’ve always had a good supply of tools, both inches and metric, and learned how and when to use them, typical brain damage :smiley:
Well, for example the 1/2"(12,7mm) socket is a real helper when it comes to a worn 13mm head (most common on standard metric 8mm bolt)
not the correct way to do it but…

The trouble is when it comes to “new” stuff where threads are mixed, and on some of these chinese made stuff there are bolts with a inches thread, and a true metric head.
And even the opposite.
When you tinker like a “robot” as mechanics often do, this, sooner or later leads to cursing…
:wink: :smiley:

Just remembered: Volvo used both imperial and metric long into 1980s, axles and stuff: inches
Brakes: inches and some mysterious British “thread”
Gearboxes: metric And inches…
Well, it’s a supplier thing, but much parts was made under license in Sweden.


They all were like that. Durring the mid to late 80’s and then into the 90’s after NAFTA was introduced. Toyota Production Systems aka ISO standardization forced the metric system into product designed. The auto industry manufacturers only assemble the vehicals. They dont make the tires, the alternator, fuel pumps, break systems. transimisions, really any of it. Thats all done by third parties and those companies also had to transition to ISO standardization. However these are big companies and changing one bolt thread somewhere with a catalog of thousands of parts is a big deal. So this createda hodgeposh mixed hardware on assemblies thoughout those years. Some companies conformed to ISO standards faster than others and some companies took years to conform.


I just look at the nut or bolt and grab my socket sets and nope to big, nope to small, nope still to small, ahh yes it fits. Simple.


One option for cooling would be a squirrel cage blower. Onan uses them for their Vacu-flo cooling on their generator engines.