Eccentric size

[DalboyParticipant @dalboy]

[DalboyParticipant @dalboy]

While watching a u tube machinist (Hobbiest for the want of a better word) they are making the Stuart s 50 eccentric the plans call for a 5/8" diameter yet the material is just under that and it would need cleaning for a nice smooth running of the rod. My question is being smaller than what the plans state would this effect the movement at the other end by shortening the stroke.

If this is true why would a reputable company supply under size material as part of a kit

Edited By Derek Lane on 07/02/2021 16:24:43

[JasonBModerator @jasonb]

It is the offset of the shaft hole from centre that influences the movement of the eccentric. Provided hole in the strap was made to suit it will be fine. Also its a generally accepted rule of thumb that any dimension shown on a drawing in fractions of an inch is +- 0.015" back in the day when pops was making his S50 all he would have had to measure the stock with would have been a steel rule and firm leg callipers, no micrometer of digi callipers!

Not seen the video (Ades? ) but if a few thou then that is quite common on bright mild steel stock which is a "nominal" 5/8"

Edited By JasonB on 07/02/2021 16:36:50

[SteviegtrParticipant @steviegtr]

I think it was Quinn.

[JasonBModerator @jasonb]

Oh dear just watched the video. IF you are making one Derek note the following.

1. The groove is not an oil groove but there for the spigot on the end of the eccentric rod to locate into so strap does not move sideways.

2. He should have clocked the part at 0.188" not 0.094" as the offset is 3/32" giving a total valve movement of 3/16"

Edited By JasonB on 07/02/2021 17:10:32

[JasonBModerator @jasonb]

Quinn is making a PMR engine not a Stuart S50

[DalboyParticipant @dalboy]

Thank you Jason I am not making one at the moment but trying to understand various items of the hobby and the learning curve is quite large at the moment.

It was just an observation and it just got my brain working. Hopefully sometime this spring I will have a new workshop to fill and make a selection as to a model to make.

Yes it was Ade's

Edited By Derek Lane on 07/02/2021 18:15:12

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