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Post by phutcheson on Feb 1, 2010 13:41:41 GMT -5
I've been looking at the details for the Side Rods mounting and I don't see anything to prevent the Side Rods from rubbing against the Drive Wheels hub. In this case it would be SS303 against 12L14. Doesn't seem to be a good match.
I was wondering what other builders (past and present!) were doing ... if anything because it may be a no issue.
Although when installing the Side Rods it easy to keep them away initially but when it is actually chugging down the track I'm thinking that they could slowly move (over time).
So ... what am I missing?
Thanks,
Pat H
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Post by GregMiller on Feb 1, 2010 20:06:16 GMT -5
Hi Pat,
I see your concern.
It looks like the bronze bushings (page 82) are the same width as the Side Rods (Page 79), 0.200". I would think that if the bushings were to be just a 'smidge' wider, that it would have been stated.
I too am curious to see what the further along builders have to say on this topic.
Greg
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Post by kenrinc on Feb 2, 2010 18:55:58 GMT -5
Pat,
Your hubs are stainless or 12L?
I wondered about this myself but haven't gotten there yet. Considering it's just around the corner for me it would be nice to know. Nelson shows a shoulder on the crankpins and the coupling rod pins in his book.
$ .02
Ken-
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Post by grege on Feb 3, 2010 8:42:00 GMT -5
Mine do rub a little- only enough to make a swirl on the wheel hub though. It isn't a bearing surface though so my opinion is that its more the aesthetic issue. The reverse crank can rub on the main rod also as it goes around. You could make some thin bronze washers or adjust rod bearing length, but may want to lengthen the crank pin to accommodate.
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Post by kenrinc on Feb 3, 2010 12:16:03 GMT -5
Good to know. I was thinking of making everything "traditional" with shoulders but then you have re-calculate everything else. Adds time to the project which catches up with you fast.
Curious why Kozo specified the rather high tolerances for the crankpin diameters. Chances for sucecss for a beginner are rather slim. Seems to me you could just use one piece of drill rod all one diameter over it's entire length and call it good.
Ken-
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Post by pkastagehand on Feb 4, 2010 11:55:49 GMT -5
I'm not that far but I would think that the incidental side load would be low enough that it would be no problem, especially if kept oiled a little.
Unless maybe you have a bent rod?
My $.04 (2 cents plus two for inflation)
Paul
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Post by phutcheson on Feb 5, 2010 14:30:22 GMT -5
Thanks all for taking a look.
Most likely it really doesn't matter. If there was a problem (or even a perceived one) it probably would have been mentioned somewhere in the forum.
My only real concern was that the drag would cause the engine to work more. Trying to keep the friction down as much as possible.
Maybe a small .005 - .010" flange on those bushings might be okay... then make up the additional amount by reducing the spacer width by that amount. Or some other combination to keep everything in line. I'll have to think on that a while ... do a little more research.
My drivers are 12L14.
Later,
Pat H
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Post by siggy on Feb 5, 2010 21:09:45 GMT -5
Yes, the side rods will rub on the drivers a bit but since there is no load on that friction point you won't need to worry about much power loss. I built mine per Kozo's plan and haven't had any issues at all with it.
Another poster wondered about the tight tolerance on the crankpins and the liklihood of success for first time builders. I think the answer is that the tight diameter relates only to the fit between the pin and the bearing surface of the rods. Since the side rods have one bearing set up with a slight eccentric, any misalignment created inadvertently by the builder can be eliminated by slightly rotating the eccentric bearing to make it fit. It works perfectly. If instead you managed the error my loosening the fit between pin and bearing you would have enough slop to oval out your bearing and cause premature bearing failure.
Robert
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Post by kenrinc on Feb 25, 2010 3:39:55 GMT -5
Robert,
The side rods do not have bearings turned eccentric. You are more than likely referring to the special "drill bushing" that is turned eccentric so that you can mount it in the side rod workpiece, turn it until it matches up with the crank pin, loctite it in place, then use it to drill the holes in the actual rod workpiece. The bearings themselves are not eccentric.
The bearing fit has come up on other forums recently. It's been proven that no slop in the rod bearings can in some cases prevent a locomotive from running or prevent it from tracking (staying on the track, esepecially on curves). Kozo shows more tolerance in the bearing to rod fit than in the pin to bearing fit (around .003). Which makes sense. That's where he's put the "slop". (actually now that I look at it, it's a total of .006" of tolerance).
Ken-
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Post by siggy on Feb 27, 2010 18:54:07 GMT -5
Yep - you're right about the side rod bearings. I guess that's what I get for trying to go from memory instead of looking it back up.
Robert
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