The Home Machinist!

rkcarguy wrote: ↑Sat Jul 06, 2019 4:03 pm It's a tall order making it sound decent. I know on my kart engine I ran the valve lash at zero (cold). When warm the lash opens up a little, but it made the clatter go away 95% and also gets every .001" of lift in the game.

That is characteristic of air-cooled engines. Aircraft engines are the same way: the cold valve lash is close to zero but opens quite a bit as the cylinder barrels heat up and get longer. The Briggs V-twin has a 0.004-0.006 valve lash spec when cold. I have mine almost at zero, which works out to about 0.018-0.020 once the engine is at operating temperature.

I was looking at the specs on the V-twins and they are more "cube" shaped and have the crank centered, would still fit inside my cab. So it's possible to stuff one of those in there in the future.

I have a machine-readable set of drawings of the V-twin, which I used to work out mounting, clearance around other parts of the locomotive, etc. Lemme know by PM if you want the file.

Thanks for the offer BDD. I will see how the GX390 works as far as having enough power and go from there. Because I have the adjustable gear ratio on the final drive I can always mount a larger drive sprocket to turn the additional HP into speed or leave it the same for more torque if I upgrade to a twin. Interestingly enough the smaller twins are only a couple ft/lb of torque more than the GX390, so it's hard to tell how it's going to do until I simply get the locomotive finished and try it out.
There is more interesting issues with lift and valve lash as well. One of my racing kart motors makes good top end but lacks a little in the tight turns, and it's sealed spec so I can't mess with the cam. So when we race the "full" 19 turn course I run the exhaust valve lash about .018" loose when cold. It sounds like a tractor but it increases the mid-torque an amount that is felt, and is good for about 2-3 10th's per lap. When we run with the technical section closed off (9 higher speed turns), I set the lash near zero for the best top end and again it's enough to feel and see. Between that and tucking my head on the straights I can pull up a couple kart lengths on each one.

I removed the GX390 from it's old pressure washer frame tonight, removed it's muffler, and sat it on the chassis to get it measured up for a motor mount. I think I'm going to cope a chunk of C8 or C10 channel and bolt it across the frame rails the wood is only to hold the engine up for measuring distances horizontally. It's tight, but with the valve cover pushed to the left as far as I can it fits nicely and will have room to spare for the hydraulic pump and housing. The header is also going to be tight, I'll have to weld up an S-bend so it clears the inside corner of the cab on the left side. A 1-3/4" stainless flex coupling(the kind with the braided stuff on the outside) is due to arrive tomorrow and will provide the movement for any chassis flex and expansion contraction of the exhaust so I don't end up chasing cracks.
The top of the air box lid is going to be really close to the inside of the cab, but it will definitely fit without the cover or if I modify it.
2nd picture is the laser cut truck parts for the bulkhead flats and my solid 2x1 rectangle bar "super duty" bolster bar and "slide bearing-(design copyright BDD )" parts just slipped together for a test fit. I'm shooting for at least a 2000# max gross weight capacity on these, so I'm making everything beefy.

Great progress!
I've enjoyed watching your work, starting as a railroad newbie with grand ideas.
It is fun to watch you forge ahead and achieve your ideas and goals. Not everyone has such success!
Keep posting, please.
~RN

Thanks NP! I have a couple aces in the hole, mainly CAD and access to the laser. I'm able to draw up all my parts, fit them together, then export them into groups of parts that are the same plate thickness and send them to the laser programmers estimator/processor. As long as I scrap bin dive for my plate which is pretty easy for these smaller parts, it's been free and I only have to pay for the laser time. Often it involves dragging a "skeleton" out of the scrap pile and cutting off the remnant I need so it's not entirely effortless.
4th and final piece of rolling stock is going to be a "extreme super duty" gondola with a "tailgate" for hauling and applying ballast to the track, it still needs to be drawn up and I also need to calculate it's capacity(gravel weight), and if I'm comfortable hauling it up down 3% grades at that weight. I'm thinking of using a pair of C8's with a 4"x6" rectangle tube down the center, then have 12ga sides laser cut.

Here we go, making the motor mount from a piece of C8x11.5:
Pic 1-Drilling the holes that will mount the engine to the channel, and channel to frame rails. I'm not welding this piece on, so I can change it in case I want to change engines and also so the welding doesn't warp the frame. I had to take the front jaw off the vice and put a piece of strapping in there so the channel would fit. Also used a roto-broach and put a large hole under the oil drain.

Pic 2-Out of the roto-blaster all cleaned up. I want to sit the engine lower, so I will be coping the ends of the channel so it drops in between the frame rails some. Also got the exhaust flange (and an extra) laser cut for the GX390 so I can start putting the header together.

I got the header all tacked up which was a multi-step process because I didn't want to take the whole frame back into work, cut, tack, test fit, repeat.
Now I can weld it up Monday and then I just need to cope the motor mount and match drill the holes in the frame and I can see how it sounds.
The exhaust piping is all oversized past the smallest part where it mates up the to GX390, for deeper tone and the ability to mount a bigger engine later if need be.

Looking good! Coming together nicely. Don’t forget to bring it down to Woodinville for a test drive!

I coped the motor mount channel during lunch and welded up the header...….and burned a small patch of hair out of my head from all the sparks lol. A reminder to always wear a welding hat even if your weld helmet wraps well up over your forehead, sparks will find a way in and hair burns nicely.
I also have a pair of 6.1 cu/in per rev. hydraulic motors on the way.

It runs! Turns out the factory muffler was rusted through in one spot and was rattling inside, it's now very quiet out of the exhaust stack-well the flange for the stack. But, I have a leak at the flange between the header and engine because I couldn't get the inner nut on the stud. I'm going to have to pull the stud and use a flange bolt that is M8 with a 10mm hex head and that will fit.

I found the right bolts and got the exhaust bolted up tight and leak free. It sounds much better but there is still a fair amount of noise coming from the engine itself, I guess that is to be expected. For whatever reason, it idled much higher plumbed through my muffler than it did with the factory one, and I was able to turn the idle down a lot more without it stalling out. It's also quieter without the plastic air cover over the air filter, which doesn't look like it's going to fit inside the cab anyway.
I changed the oil and it looked pretty good, no glitter or chunks or anything. I refilled it with some petroleum base Maxima 4 10w-40, which is my go to for everything because it's 2nd in zinc content to Amsoil.

I ran the engine for awhile longer about 20 mins, pretty happy with the muffler. The outside only gets a little warm to the touch the rock wool seems to really help, I'm sure under load it will be hotter but I'll be moving too so I don't know if it will be that much different.
Tonight I'm cutting the "firewall" out of the cab front so the body will fit over the engine and exhaust.