Engine Question


Old 03-09-03, 11:51 PM
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Exclamation Robin (Subaru) Engine "loping"

I have a serious problem. I hope that somebody can help me out. I am building a gas powered portable welder out of a Robin (subaru) 7.5 h.p. horizontal shaft engine (model ey28) and an alternator. i have them both mounted on a steel plate that has feet on it. My problem is the engine "lopes". it vibrates the whole platform and if I run it for more then 2 minutes it'll end up on the other side of the shop. I placed rubber grommmets between the engine and plate which helped a little, but it's still walking across the floor. I'm thinking if I mount the plate to a frame and pnuematic tires to the frame this should dampen the vibrations considerably. Am I correct? If that doesn't work, I have 4 trampoline springs I could mount to the plate and suspent that on the springs from the frame. I've been told that won't help though because the springs will still pull the frame, causing it to move still. I've also had the idea to use shock absorbers (like the kind you would use on a small go-kart) mounted to the plate and then to the frame. I really don't want to spend that much money on the shock absorbers though if I'm not positive they'll work. You can find the engine on surpluscenter.com. I'm 99% positive it's not my cast iron 5 1/2" pulley I use to drive the alternator because I have the same engine for a go-kart and it "lopes" also without a pulley or anything on the shaft.
If somebody could give me some suggestions I would greatly appreciate it.
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Old 03-10-03, 06:12 PM
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Hello meyn, I have three experiences that may give you some thoughts. To bench run horizontal shaft engines without a 500 lb. bench I came up with a base from a pump that cushioned the engine by using four 1 1/2 inch springs by two inches tall with the mounting based attached to them. A quarter inch rubber mat on the base finished the deal and I get little if any vibration.
I had a 12 hp Kohler horizontal that lost a motor mount on a John Deere and I couldn't believe how hard that 12 was hitting. The engine seems to hang in its mounts and moves rather freely compared to a vertical rigid mounted engine.
I have a Mazda that uses the dogbone type of mount and it is really a big version of the John Deere style and the key to using rubber grommets is the bolt is always rather loose in the mount allowing a great deal of play.
Hope this helps some......Mike
Old 03-10-03, 08:32 PM
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Thanks for the advice Mike. I saw the spring idea in a Northern tool catalog on a pump. It looks like a good idea, but I would have to do quite a bit of fabricating for the "base" on either side, wouldn't I? Could you give me a little more detail on that setup? Here's the link for the pump I would like to model mine after.
Did your base look something like the one in the link? How did you attatch the springs to the base? I dou have a welder. Do you think my idea will work with suspending the plate with the engine on it in the frame with the springs? It sounds as if that's pretty much how your John Deere is set up, only with rubber. If I did use either spring idea, do you think I could just use mu grommets instead of laying down a pad? I do have the bolts rather loose, with locknuts on them. There's quite a bit of play in them.

Do you think the pnuematic tires will help any? They should dampen some of the vibration I would think. I'm thinking if I build anymore of these they will be with a vertical shaft engine. Do you know why the horizontal shaft engines do this?

Well, I appreciate you taking the time to answer my question. Thank you.
Old 03-12-03, 05:04 AM
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Sorry about the delay, I had to make a trip to the shop to see how mine was made because I didn't build mine, I just adapted it to my needs. My base is almost exactly like the one at the link you posted except smaller with 4 larger springs instead of 6. It is held together with flush mount screws run from the top down through the upper rails, through the middle of the springs and into hole in the lower rails. There is just enough tension on the screws to hold it all together and locking nuts are used. I used mine without the the rubber pad for a long time and added it to help keep my tools on the bench. I think the rubber grommets would serve the same purpose if you need them at all. Your suspended plate would work well if the extra room it takes works for you.
Smaller horizontal engines seem to vibrate/hit harder that vertical due to the forces pounding down onto whatever its mounted to rather than forces which are horizontal to the base. Somewhere along various engine makers lines, usually about 8hp, they go to a counter balance system that offsets the vibrations in the engine......Mike
Old 03-18-03, 04:33 PM
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Thanks Mike for the help. I had another friend of mine look into a remedy for this problem and we solved it. we just went with the pnuematic tires and they work great. They're 10" x 2.5". I just let a little bit of the air out of them to soften them up. The store had them at their max p.s.i.. This was a much cheaper and easier remedy. The tires only cost $4.99 each, plus $5.89 for the 5/8" axle. It was well worth it though. Now I can take the welder anywhere.

By the way. I am now producing these welders at an unbelievable price. For a gas powered, 7.5 h.p., portable welder we are asking $700 + s/h. If you know of anybody looking for one they can e-mail me at [email protected]. The best I can do for them now is a few pics of it and a description.
Thanks for the help

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