Author Topic: Building a model Drag Saw  (Read 6875 times)

Offline Tennessee Whiskey

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Re: Building a model Drag Saw
« Reply #135 on: September 20, 2018, 12:49:22 AM »
Just wonderful Brian; do MEM members get a discount on the plans?

Whiskey

Offline Dave Otto

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Re: Building a model Drag Saw
« Reply #136 on: September 20, 2018, 01:18:55 AM »
Nicely done Brian!

Dave

Offline Brian Rupnow

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Re: Building a model Drag Saw
« Reply #137 on: September 20, 2018, 01:35:15 AM »
Just wonderful Brian; do MEM members get a discount on the plans?

Whiskey
That is my discounted price. Designed, detailed, built, de-bugged, and operational.

Offline Jasonb

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Re: Building a model Drag Saw
« Reply #138 on: September 20, 2018, 07:21:56 AM »
Just wonderful Brian; do MEM members get a discount on the plans?

Whiskey

By the time Brian has paid out all those who have helped him with info during the build there won't be much left for him if he discounts it any more :LittleDevil:

I think the two knots had more effect on the time it took to cut the first log than the blade, looking at the videos they both take about 30secs to get to the same point where the knots start. I wonder if the linkages were made from steel rather than aluminium if you would get a better cut as there would be more weight on the saw blade though that may start to bog down the engine.
« Last Edit: September 20, 2018, 08:21:29 AM by Jasonb »

Offline Brian Rupnow

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Re: Building a model Drag Saw
« Reply #139 on: September 20, 2018, 01:57:48 PM »
Jason--You may have missed it in an earlier post.--all of the saw links are made of steel. If they were aluminum, the saw wouldn't feed at all. The knots definitely had an effect on the cut in the first video. The saw is not bogging down at all, so I could safely add weight to the mechanism. The problem is that when I start adding weight anywhere, it looks less and less like the original dragsaw it was patterned after.
« Last Edit: September 20, 2018, 06:40:28 PM by Brian Rupnow »

Offline NickG

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Re: Building a model Drag Saw
« Reply #140 on: September 20, 2018, 08:40:58 PM »
Great project and result Brian, I might be way off the mark here but could the log be set too low? It looked at the end like the blade was being pushed down into the log, shouldn’t the angle mean it is pulling down into it on the back stroke? Anyway, it worked well and I think the blade you used can cut on front and back stroke?


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Offline Brian Rupnow

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Re: Building a model Drag Saw
« Reply #141 on: September 20, 2018, 08:53:19 PM »
Nick--It's all in the position of the pivots and the lengths of the arms. When the saw blade is held up by the log it takes on a totally different path as it strokes than when the main overhead arm is held up by a bolt underneath it to prevent from the saw cutting too deeply and plowing into the ground at the end of the cut. When the saw is setting more or less level on top of the log, it maintains that level, but as the saw drops thru the log the saw takes on more and more of a tilt in the swing as it gets lower and lower. There is a "range" of where the saw stays level, but above or below that rang, the saw tilts more and more.

Offline Craig DeShong

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Re: Building a model Drag Saw
« Reply #142 on: September 21, 2018, 02:08:05 AM »
Nice Brian.  I've seen a few of these in operation and your model really mimmicks the "real thing".  :ThumbsUp:
Craig

Offline Larry

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Re: Building a model Drag Saw
« Reply #143 on: September 21, 2018, 04:04:49 AM »
Love watching these at engine shows - another great job !