# Building a model Drag Saw



## Brian Rupnow (Aug 28, 2018)

I am going to build a model drag saw. The power for this saw will come from the second i.c. engine I ever built--The Kerzel hit and miss engine. There are so many things that I don't know about a drag saw that it makes my head vibrate, but I am a fast learner. I am going to use a driving mechanism similar to the one in the attached picture.  One of the first things I have to design is a "dog clutch" which enables me to shift a lever and put the engine "out of gear" so that I don't have to shut the engine down to stop the saw blade moving. I have at one time or other built everything in a drag saw (on other machinery) except for a dog clutch. Since I have the capability to cut my own gears, this saw will have a gear drive instead of a sprocket and chain. If you like this sort of thing, then follow along. Parts of this story may be boring, but parts of it will be something new.


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## Brian Rupnow (Aug 28, 2018)

This first bit is a head scratcher. Where do I start?--well, the green colored part is the available shaft end and flywheel hub on the side of the Kerzel opposite from the governor weights. It is 3/8" diameter x 1.125" long. The brown colored part is a steel shaft extender 3/8" i.d. x 7/16" o.d. that slides over the Kerzel shaft and is pinned there by a 3/32" diameter cross pin. (And maybe some Loctite). The dark blue gear is a 24 dp x 20 tooth gear which has an internal bore of 1/2" and has a bronze bushing (red color) pressed into it. It also has three "dogs" machined on one side. It actually "floats" on the shaft extender and is not keyed to it in any way. There is a shoulder on the end of the brown shaft extender which the gear rides up against. The  pink part is a steel sliding bushing with three "dogs" machined on it that will fit into the three slots between the dogs on the blue gear. It has a "groove" machined into the outer diameter, which a pair of pins on the shift lever fit into. It is capable of sliding along the shaft extender, and is also keyed to the shaft extender so it can not rotate freely. (I haven't quite worked that last bit out yet.)


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## Brian Rupnow (Aug 28, 2018)

Okay---I got it!! Two pictures here, one with dog clutch engaged and one with dog clutch disengaged. The green cross-pin on the extreme right hand end is for my electric starter.


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## Brian Rupnow (Aug 28, 2018)

This is it for today. Since I have now modelled the dog clutch, I will decide whether to stop designing and make some real metal parts or do some further design tomorrow.


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## Brian Rupnow (Aug 28, 2018)

I may very well put a ramp on the driving dogs. I just did a little test out in my main garage. I put a spruce 2 x 4 in my vice and got one of my handsaws. My son was here and had a stop watch built into his cell phone. I sawed at what seemed to me to be a reasonable speed, and he timed me for three different 10 second intervals. Seems like 14 strokes per 10 seconds is "reasonable". Six times 14 equals 84 strokes per minute. The ratio between my two gears is 108 divided by 20 equals a ratio of 5.4 to 1   So---5.4 x 84=453 rpm at the engine crankshaft. I don't remember what speed my Kerzel engine runs at, but I will probably start it tomorrow and check it with a laser tachometer. I know my single cylinder flathead engine runs at about 1000 rpm. I think the Kerzel runs slower than the flathead, but I will have to check it and see. If I have to have a second stage gear reduction built into this drag saw to make it work, I would much rather know now at the design stage than after it is all finished.


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## minh-thanh (Aug 29, 2018)

Use the engine to do something
I like this idea !


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## Brian Rupnow (Aug 29, 2018)

First thing to do this morning was machine ramps on the driving dogs. Others have told me this makes the dog clutch much easier to engage. Now I'm off to my garage to start the Kerzel engine and decide what rpm it runs at.


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## werowance (Aug 29, 2018)

so how will the clutch engage/disengage while running?  some sort of lever mechanisim running int he grove on the purple piece?  or some sort of spring loaded setup?  I'm just not understanding the mechanics of that part.  at least not the ability to do it while running.


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## Brian Rupnow (Aug 29, 2018)

I set up the Kerzel engine this morning and ran it. My laser tachometer tells me it is turning at 960 rpm. This is twice as fast as I require, in order to get the saw to make 12 to 14 strokes every 10 seconds. I can not make the engine run any slower, so I will have to put one more set of gears in the drag-saw gear train. I currently have a 5.4:1 ratio in the gears on the saw, so I will have to install a second set of gears at 2:1 ratio to give an engine speed of about 900 rpm.


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## mortimer (Aug 29, 2018)

the square dog clutch ,under load is Very difficult to disengage.   I have made then with a 1 degree taper to assist with Dis-engagement. on the last one I used,  the motive power was 15 Kw and 50 RPM


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## Brian Rupnow (Aug 29, 2018)

Werowance--A swinging lever with two pins which engage the slot in the purple/pink sliding dog.


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## a41capt (Aug 29, 2018)

Following your build Brian.  As usual, you have some great ideas here.  Even though the load on a model may not be that heavy, you may find that a single pin on your sliding clutch is inadequate.  Splines can be a pain, but that may be required to ensure that you don’t sheer off your pin during engagement from a standstill.

Looking forward to seeing it in action!

John W
Camp Verde, AZ


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## Brian Rupnow (Aug 29, 2018)

I've spent 6 hours today in "geometry world", coming up with a set of linkages that will work for the drag saw. I know of no set of equations that will let you calculate this stuff. It is more "try it and see" engineering. What I have here is a set of linkages that go through all of the required motions without binding or going into a "lock" position. Now I have to take the time to do a visual comparison between what I have and what a real drag-saw looks like. This is fun stuff, but it isn't easy. Before I cut any metal, I will build these linkages full scale in cardboard and using "stick pins" work it through all of the required motions.


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## Brian Rupnow (Aug 29, 2018)

I am having second thoughts about using the Kerzel engine with the drag saw. The Kerzel has a 3/4" bore, while the Odds and Ends engine has a 1" bore, larger flywheels, and is all around a bigger engine. I'm looking at the size of the Kerzel compared to the larger  Odds and Ends hit and miss engine and I think the Odds and Ends engine would be a better choice.


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## werowance (Aug 30, 2018)

ok, I get it,  like a clutch fork on a throw out bearing.  now I'm jumping way ahead and wondering what the saw blade will be made out of,  I realize a lot of linkages and ratios to work out before you get to that point but just curious.


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## Brian Rupnow (Aug 30, 2018)

Probably a keyhole saw.


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## Brian Rupnow (Aug 30, 2018)

Okay--Got that sorted. The engine is now the Philip Duclos "Odds and Ends" hit and miss engine. In order to get from 1000 rpm at the crankshaft to 84 rpm at the disc which the saw arm attaches, and to fit the constraints of what I have, there are actually two gear reductions coming off the engine shaft and one roller chain reduction. Part of the reason there are two gear reductions is to get the disc spinning the same clockwise rotation of the engine, and to get that large 108 tooth pulley with the spokes far enough away from the engine crankshaft to enable getting a cross shaft underneath the engine to reach the far side of the engine where the chain and sprockets will be. I haven't changed anything on the drive disc and linkages which are shown.


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## Brian Rupnow (Aug 30, 2018)

I pulled the flywheel off of the starter side of the Odds and Ends hit and miss engine. It appears that I will be able to make my dog clutch work on this side and still be able to use my electric drill starter. I am proceeding with more layout work on the drag saw mechanism and frame.


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## Brian Rupnow (Aug 30, 2018)

This thing is going to be big!! I'm pretty sure I have all the calculations right. The log is 3" diameter which is fairly close "scale-wise". The keyhole saw I inherited from my father and haven't used in 20 years is going to provide the blade for this beast.


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## Brian Rupnow (Aug 31, 2018)

Someone said that a journey of 1000 miles begins with one step. The only thing on this drag saw that I haven't made before is the "dog clutch". So---that is where I will begin. The design is going to be marginally different from the one in the attached 3D model because of minor differences in the output shaft on the Odds and Ends engine from the Kerzel.


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## Brian Rupnow (Sep 2, 2018)

Today I machined the crankshaft extension for the Odds and Ends engine. There is more to this extension than meets the eye. It has two counterbores machined on the far end, one to precisely fit the flywheel hub, and one to match the 1/2" length of crankshaft that extended past the flywheel hub. The end you can't see is drilled and tapped six places to match the clearance holes in the flywheel. You can see that in the pulley I removed in order to fit the extension on. In a perfect world, there will be no wobble in the end of that shaft extension when the engine is running. The 20 tooth gear, bushing, and drive dog will all be fitted to this extension. I machined two grooves in the large outside diameter of the extension  in case I want at some point to drive o-ring drive belts with this engine.


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## Brian Rupnow (Sep 3, 2018)

Today has been mostly cad work, figuring out the overall layout, how part A connects to point B, etcetera. I still have to find room for a gas tank, as the one currently on the Odds and Ends engine will be in the way. I'm liking this. The log being sawed is 3" diameter.


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## Brian Rupnow (Sep 3, 2018)

This shows the dog clutch lever  by itself and how it assembles to the drag saw, where it pivots on the axle. It moves very little to engage or disengage the dog clutch. Right now I'm not sure how to make it stay "in gear" or "disengaged". There isnt enough movement to use ball detents`. Maybe a couple of spring washers and a bolt through the bottom pivot?


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## Brian Rupnow (Sep 4, 2018)

This morning I even found room for a gas tank. I also changed the two members that reach from the engine up to the log. I originally had them as 1/2" round rod, but all of the drag saw videos show them as being rectangular wood. I'm getting close to the point where I start cutting metal.


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## Brian Rupnow (Sep 4, 2018)

Today I finished most of the detail drawings and machined the gear half of the dog clutch. It may prove interesting to make the other half.


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## Brian Rupnow (Sep 4, 2018)

Something in my black old heart tells me that both parts of the dog clutch should be hardened, then "drawn back" to a point where they are tough but not brittle. My heat treat capabilities are limited to oxy-acetylene torch and my wifes kitchen oven. I already had the gear, made from 1018 mild steel so can't heat treat it, but I am going to machine the drive dog tomorrow, and it just happens that I do have a piece of o1 material the right diameter. I will machine it to size, heat it to cherry red with my torch, then drop it into a container of oil. Then 2 hours in my good wifes kitchen oven at 350 degrees F for two hours.


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## Brian Rupnow (Sep 5, 2018)

Hark Hark--The dogs bark!!! Dog clutch is finished and will engage and disengage as I had hoped. A lot of fussy set-up, but turned out great. Pictures show it engaged and disengaged.


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## Brian Rupnow (Sep 5, 2018)

All the gears that will be used in the drag-saw are finished. The largest and smallest were "repurposed" from the walking beam project. The center gear was just finished 15 minutes ago, and I'm done for the day. My back is killing me and I have to go across town and pick up some aluminum from my supplier.


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## Cymro77 (Sep 6, 2018)

Brian, I think a back massage should be the order of the day!  I love your way of working through problems.


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## Brian Rupnow (Sep 6, 2018)

So far today, it has been "work like Hell and not accomplish much" kind of a day. I did drill and ream holes in a piece of scrap at the calculated gear centers, and all seems to be fine. Gears mesh with no binding. In the picture they are running in the mill with lots of oil on them. I will let them run for 15 minutes or so before tearing the set-up down. Now, I have a calculated number for the sprocket centers, and will test the chain and sprockets the same way, after I have shortened the chain to the appropriate number of links.


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## Brian Rupnow (Sep 6, 2018)

My calculation for sprocket center distance seems to have been "right on". After a half hour struggle with the master link it all goes together and looks about right. Not under tension but not a lot of slack either. The uglies on the face of that large sprocket are a testament to just how bad my vision is getting for welding things. A little J.B. Weld will fill those cavities. I buy my sprockets as "flat" sprockets with no center hub. I make up my own center hubs and weld them in.


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## Brian Rupnow (Sep 6, 2018)

Cymro77--Thanks for stopping by and leaving a comment. It helps me with my builds when I know people are interested enough to have a look and maybe say Hi.---Brian


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## nel2lar (Sep 6, 2018)

Brian
Very nice start and it looks like you have a good plan. I'm watching.
Nelson


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## Cymro77 (Sep 6, 2018)

Brian, you are welcome.  I watch all of your builds, have even built one of your beam engines.  Thanks for the learning experiences.  DW


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## werowance (Sep 7, 2018)

that spoked hub gear - the large one sure is nice to look at.


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## Brian Rupnow (Sep 7, 2018)

Hello Nelson--Good to have you following. Werowance--That large gear with the spokes wasn't difficult to make, it was just time consuming.--Brian


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## Brian Rupnow (Sep 7, 2018)

Progress is being made. This morning I finished the 1/2" thick engine sub-base which connects the engine to the rest of the components underneath, and gives me an alternate place to mount a gas tank. The original gas tank on this engine was mounted to the side where you see the two socket head cap screws, and would have been in the way. The next plate I make, which is going to provide a place for the 108 tooth gear shaft and the 30 tooth gear is going to be a challenge.


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## LorenOtto (Sep 7, 2018)

I am following with interest also, Loren


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## Brian Rupnow (Sep 7, 2018)

The complex endplate is roughed in using the bandsaw, and tomorrow will be milled to finished size. That 1 1/2" hole bored in the center is cosmetic, nothing more. The large sprocket with the shabby welding showing on the one face was treated to some J.B. weld, left overnight to harden up, then painted with a rattle can. A little paint hides a lot of sin!!


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## nel2lar (Sep 7, 2018)

Brian
My brain is going faster than you can machine. Question: How are you going to connect the saw to the drive with the engagement lever where it is? I've always liked the drag saw and yours is looking to take shape. 
Enjoying it all.
Nelson


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## Brian Rupnow (Sep 7, 2018)

Nelson If you look at the very first post, I think that you will see that the engagement lever on my model is in the same place as the one on a full size saw. As I understand it, first you started the engine with the lever not engaged. Then you grabbed a handle on the parallelogram and lifted the saw blade so it was not touching the wood, then you engaged the lever and after the saw started moving you set it on the log so the weight of the mechanism would make the blade cut.---Brian


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## nel2lar (Sep 7, 2018)

Brian
I can almost see it, but I be watching
Nelson


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## Brian Rupnow (Sep 8, 2018)

That went very well!! The riser plate is finished and installed. The gears all mesh perfectly. I have a couple of shafts to shorten, but all in all I'm happy with the way that turned out.


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## Brian Rupnow (Sep 9, 2018)

This morning I completed the other riser block, which serves as the bushing holder for the large sprocket shaft and also gives a place to bolt the two long rectangular "handles" to. I have removed the engine from the drag saw platform to make some adjustments to it before reassembly. The chain fits as I had intended, with no last minute surprises. While I was boring this last piece  in the lathe, I managed to turn out the tailstock spindle too far and it all came apart, so now before I do any more work, I have to figure out how that goes back together.


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## nel2lar (Sep 9, 2018)

Brian
My mistake, I was not looking at the countershaft in front of the engaging handle. I was thinking it was on the same shaft. I can not wait to see it saw.
Keep it coming.
Nelson


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## propclock (Sep 10, 2018)

I am enjoying your build also, Go Brian!


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## te_gui (Sep 10, 2018)

One of the potentially exciting quirks of many drag saws is they were two-strokes. You pull them up and bounce them against compression to start , but  they are almost as likely to start in reverse as well. It gets very exciting when you drop the saw onto the log and the whole thing attempts to fling itself over backwards, and then thrash about until you can hit the kill switch.


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## Brian Rupnow (Sep 10, 2018)

Today is a milestone in the drag saw build. I wanted to be certain that the Odds and Ends hit and miss engine had sufficient power to cope with the gear train of the drag saw. It handles it with no difficulty, which is great. Now I can proceed with the rest of the build.


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## Brian Rupnow (Sep 10, 2018)

Nothing real exciting machined today. Just an axle. The real, full sized drag saws had short stub axles, each attached to a pivot so the machine could be dragged along using the handles, or the wheels could be turned at 90 degrees to help prevent the drag saw platform and engine from moving as the saw cut through the log. Obviously, I'm not going to do that with mine. Mine will have the handles pinned to the log to prevent the platform and engine from moving as the saw cuts. If you look closely, you can see the 3/16" hole thru the right hand end of the axle where my dog clutch arm will pivot.


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## Brian Rupnow (Sep 10, 2018)

I've  got a little mystery to solve here. The engine runs at 1000 rpm. I have an overall gear ratio of 12:1. That means the piece of tape should be turning  1000/12=83.3 rpm, which equals 13.9 times per 10 second interval. I just had my son count of 10 seconds on his cell phone/stop-watch, and it looks like the tape is going about 20 complete turns per 10 second interval.--Which would mean 120 rpm, which multiplied by 12 gives an engine rpm of 1440 rpm. Check the video and tell me how many revolutions that piece of tape makes in a 10 second interval.---Brian


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## nel2lar (Sep 10, 2018)

Brian
I watched the video in Windows Media Player
 When you click a restart point in the progress bar, the clock starts over and I counted several times to get 12 or 13 rotations.
Maybe others will help you out on this.
Nelson


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## nel2lar (Sep 10, 2018)

Brian
I sit here watching the video and tried to imitate the holding a saw and keep up with your flag and I find it just about right. I am not rushing to keep up with it and it feels right.
Looking good my friend
Nelson


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## TonyM (Sep 11, 2018)

Hi Brian
I just checked at 1/4 speed and got 9.5 revs in 5 seconds so 19 in 10 seconds. 114 rpm 1368 engine rpm so pretty similar to yourself. I checked at three different points on the video and got 10, 9.5 and 9


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## nel2lar (Sep 11, 2018)

Brian
What would work a lot better than visual is a mechanical tachometer. There are many out there and I found some on EBay:
https://www.ebay.com/sch/i.html?_fr...=0&_odkw=mechanical+tachometer&LH_TitleDesc=0

The price has gone wild since I bought mine but it not that bad, and they are accurate.
Good Luck
Nelson


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## Brian Rupnow (Sep 11, 2018)

It isn't a huge problem. That sought after 14 strokes in a 10 second time interval was based on me sawing a pine 2 x 4 with a handsaw. It probably won't hurt is the saw runs a bit faster. I have lots of room on the roller chain side to put on a larger sprocket to bring the speed lower if I need to. Thank you for confirming my count.--Brian


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## Brian Rupnow (Sep 11, 2018)

And there gentlemen, you have the long and short of it.--mostly the long. I knew right from the beginning that this was going to be a lengthy beast, and this just confirms it. The notches in the underside of the rails, out at the end opposite the engine, is for a cross-beam that bolts on and can be "pinned" to the log to keep the main saw body from dancing all over the place during a cut. The notch in the top side is for a beam with an adjustable stop on it that prevents the saw blade from trying to dig a hole thru to China after it has passed thru the log.


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## Brian Rupnow (Sep 12, 2018)

So--We're getting right down to the "short steps" of this monster. Today I made and installed the two cross-members  that fit between the frame rails, the brass "Handgrips" at the end of the arms, and the 4" diameter wheels. I still have to make an arm to control the dog clutch, and all of the parallelogram links in the saw mechanism. I went and looked at saws today, and nothing really appealed to me. Then I called a saw sharpening service here in town, and they charge $10 to sharpen a saw and $4 extra if they have to "set" the teeth. I have about 4 or 5 handsaws that I inherited from my father---They are all dull. I made an appointment to see the saw sharpener tomorrow and I will take my collection of handsaws over to him and explain what I am doing and have him sharpen one of the existing cross-cut saws to use on this project. I may use the keyhole saw I showed earlier in this thread. The only part of the entire machine that motivates the saw to cut thru the log is the weight of the saw blade and the parallelogram arms, responding to gravity. The arms will all be made from steel.


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## nel2lar (Sep 12, 2018)

Brian
Beautiful, You  have a special touch, down right gorgeous. 
I'm lovin it.
Nelson


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## Brian Rupnow (Sep 13, 2018)

I went over this morning and took three of my dad's hand-saws to the saw sharpener guy. I explained to him what I was making, and asked which of the saws would have the best tooth profile for the drag saw. He had a look at them and said that none of them had been sharpened correctly in the past, and there wasn't a lot he could do to sharpen them. Then he went over to a rack of used saws that he had sharpened and no-one had picked up, and he gave me one, newly sharpened, with the correct tooth profile. I gave him two of dads old saws in return, because I've had them over twenty five years and never used them. I am currently working on the parallelogram links to mount the saw blade.


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## stragenmitsuko (Sep 13, 2018)

Beautifull work as usual . 
Can you elaborate on the tooth profile . 
Does a drag saw need a different profile from a hand saw ? 
When sawing by hand , the cutting action ison the forward stroke , hence the 
teeth are a bit tilted forward . 


I guess next will be a model log splitter , and then maybe a fireplace ...


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## goody (Sep 13, 2018)

Nice,   I have a full sized Vaughn drag saw which is currently in a logging museum in Northern California.   My older brother restored it 20 years ago.   The bar is 2 parallel rails about 3 feet long the clamp for the blade mounts on the rails and travels about 2 1/2 feet the whole bar pivots from the rear.  The blade is 6 foot long with 2” double cut teeth, the pitman arm is roughly a foot long and drives to the center of the slide.  Stroke rate is around 60 per minute.


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## goody (Sep 13, 2018)

So I did a google search for the Vaughn and a YouTube video showed up of my older brother running the saw at a show in Idaho. If you want to watch one in action.


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## Brian Rupnow (Sep 13, 2018)

Today was one of those days when I spent more time figuring out how to make some of the parts than I did making the parts. The first three parallelogram arms are semi finished and shown in place.


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## Brian Rupnow (Sep 13, 2018)

Goody--There are two types of drag saw. the one you are describing, and the other type which I am building, with a set of parallelogram arms. See the very first post in this thread to see the type I am building.---Brian rupnow


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## nel2lar (Sep 14, 2018)

goody said:


> So I did a google search for the Vaughn and a YouTube video showed up of my older brother running the saw at a show in Idaho. If you want to watch one in action.


Goody
How about a site we can go and see that saw and it's working. The industrial age brought out all kinds of invention. It just goes to show we are always looking for an easier way to do chores that must be done.
I found the videos and they are all so very much alike with added features like the
*Ottawa Model T.E. 4HP and 5 HP Drag Saw**, *which the transport wheels would turn 90° to be used as stabilizers while cutting. Very interesting how one persons mind works to another, I  suppose it had to do with patent violations. 

Nelson

for those interested in additional saw look here:
https://www.youtube.com/results?search_query=Vaughn+drag+saw


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## Brian Rupnow (Sep 14, 2018)

It doesn't look like much, but I have a full days work in these parallelogram arms. Each arm has oilite bronze bushings at the pivot points. The actual pivot pins are 3/8" shoulder bolts. I got very lucky and discovered that one of my slitting saws was the same width as the saw blade I plan on using, so the bottom link is slit and ready to accept the saw blade. Tomorrow I will possibly make the crank arm and the connecting link. I was a bit concerned about there being sufficient weight in the arm assemblies to force the saw into the cut, but now that I have the arms almost finished I see that there will be sufficient weight.


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## Brian Rupnow (Sep 14, 2018)

Check out this video of a drag saw with parallelogram action, same as the model I am building. Notice that the wheels are NOT turned at 90 degrees, but are positioned the same as the wheels on my model.---Brian


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## Brian Rupnow (Sep 15, 2018)

As I say in the attached video, "We're almost ready to rock and roll." I need to cut out my saw blade and machine a lever to operate the clutch and then I think we will be ready to cut up a log.---Brian


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## Brian Rupnow (Sep 15, 2018)

And for those of you who asked "Where do you get a blade" and "You know those saws only cut on the pull stroke." Here is where you get the blade with the teeth cutting in the correct direction. About 10 minutes work with a die grinder and an abrasive wheel. I wrapped a piece of steel bar with a wet dish cloth and laid it over the part of the saw I wanted to keep so the heat wouldn't warp it. Now if I'm really lucky, I will be able to carbide two 1/8" diameter holes in it to bolt it on.


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## Brian Rupnow (Sep 15, 2018)

I may have to rename this thing the Pinnochio saw---


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## nel2lar (Sep 15, 2018)

Brian
How sweeeeet it is, beautiful. You have done a very nice job on tha Pinnochio Saw.
Can not wait to see it in action. Very nice.
Nelson


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## Brian Rupnow (Sep 15, 2018)

I have a laymans knowledge of handsaws. My dad was a carpenter when he wasn't lumberjacking, so I know the difference in a cross cut saw and a rip saw. I have a vague notion of what "raker teeth" do. My saw knowledge stops about there, and although I am aware of "pit saws" and "ice saws", I have no idea as to the tooth profile. I have never seen a "real live drag saw" other than a couple of weeks ago when I seen one that wasn't operating at a steam show in Milton Ontario, and it wasn't the type which I am building. You folks have no idea of how desperate I get to find something mechanical that I haven't already built. This has been a fun build, and I am in the home stretch now. I may even give this thing a test drive tomorrow, but only on a pine 2 x 4. I won't make a video until I  can find a 3" diameter round of dry cedar or pine with the bark still on it. I still have to build the handle which engages and disengages the dog clutch, but that won't stop me from taking a test drive.


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## Brian Rupnow (Sep 16, 2018)

I am about to finish the final parts of this drag saw. If you have followed this post, you will know I am using a dog clutch which is engaged and disengaged by a lever. I have watched two dozen videos of drag saws on YouTube, and I'm still not certain of what type of clutch they used--it isn't clear in the videos. If anyone has detailed knowledge of how these original drag saw clutches operated, now would be a really good time to contact me and let me know. I have heard that they too have lever operated dog clutches, but I have also heard that they had friction clutches which gave them a gentler engagement than a dog clutch. If anyone has this knowledge, I would really appreciate a heads up.---Brian


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## nel2lar (Sep 16, 2018)

Brian 
I was looking back through some of your builds and there it was. Take a look at your sawmill build and the way you engaged it, it might work better on this.
Nelson


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## Brian Rupnow (Sep 16, 2018)

The cone clutch on that sawmill set up works great, but if you looked closely you will see that after the clutch is engaged, there is a spring loaded toggle that pops up and holds the  engagement lever in place. And--That spring loaded pop up lever has to be depressed before the handle can release. It works great, but there are a lot of parts there to fit into a simple handle.


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## Brian Rupnow (Sep 16, 2018)

Today I finished the dog clutch engagement lever. I realized that I had no way to put in the fancy scallops on each side that are shown in the cad model, because the handle is too long to swing on my lathe faceplate. If I can make it work properly, I may drill a series of cosmetic holes down the face below the hole that fits over the clutch diameter. Right now it works fine as far as engaging g/disengaging the dog clutch goes while the engine is not running, but there is nothing to make it stay engaged or disengaged. I have been warned that it is difficult to disengage the dog clutch while the engine is running. If that is true, perhaps I can just install a light spring that makes the lever disengage when no other forces are applied to it.


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## nel2lar (Sep 16, 2018)

Brian
Another idea. Do you think a ball detent down through the handle with a couple small spots on the shaft to engage in and out. 
Just an idea.
Nelson


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## Brian Rupnow (Sep 16, 2018)

Nelson--If there was a greater range of movement, I would do that. The movement at the clutch components is less than 1/4", so the handle doesn't move enough near the pivot point to use a ball detent.


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## nel2lar (Sep 16, 2018)

Brian
Another one down,
Good luck
Nelson


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## Brian Rupnow (Sep 17, 2018)

So--We have confirmation that everything goes round and round and up and down when the saw is operating but not actually cutting anything. Next step will be for me to tramp around in the woods behind my place and find a real 3" diameter log to cut.


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## werowance (Sep 17, 2018)

nicely done Brian, curious,  how does the engageing lever "feel" to the hand when engaging it?  is it like a clunk or thud,  or does it feel like grinding gears when trying to shift a car without the clutch pedal push?  or does it just feel like a clutch?  it seemed to engage very easily for you.


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## Brian Rupnow (Sep 17, 2018)

So--Today the drag saw cut it's first log. Everything went very well, except that I need to get a more aggressive blade. About half way thru the log, the saw seemed to take forever until I gave it a bit of extra weight from my thumb. A picture taken after the cut shows that there were two knots hidden away in the center of the log. Everything works as I hoped it would. My dog clutch worked as I had hoped. (I never made one of them before).  I will post another video after I get a more aggressive blade and put a spring on my dog clutch lever to keep it from rattling. I sell a complete set of drawings for this drag saw for $25 Canadian, but that does not include the engine.


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## Brian Rupnow (Sep 17, 2018)

Werowance.  I guess I could say it starts with a "clunk". There is nothing gradual about it. One second it is disengaged, the next second it is all in action. I wouldn't try to use a clutch like this on anything that was under a load and needed to be started gradually.---Brian


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## werowance (Sep 17, 2018)

add a hack saw blade and you would have a power hacksaw     very nicely done Brian.


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## nel2lar (Sep 17, 2018)

Brian
Very nice build and it is all you wished. You mention how it was depositing saw dust to both sides of the log, that is normal because as the cutting stroke ends it has dust in each tooth that has not cleared the log carrying it in the back stroke and dropping it. A very nice video showing what a little bit of metal and the right person can do. Excellent job. 
Nelson


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## goody (Sep 17, 2018)

So dad’s Vaughn did use the dog clutch I think it had 4 dogs on it and I seem to remember a canvas or leather, possibly belting pad that worked like a synchronizer to bring it to speed but that was 60 years ago and I only saw it run once bucking up logs to be split.   I didn’t get a chance to run it after my older brother rebuilt it in 1998. I could call the museum and see if they could send me a picture.  In the YouTube video you can see the clutch being engaged, but no details.    

Pat


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## Ghosty (Sep 17, 2018)

Brian,
Another brilliant build, congrats on the saw. You may need to look in the hardware shops where the saw blades for the sawalls blades are kept, some of them have an aggressive tooth design.

Cheers
Andrew


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## Brian Rupnow (Sep 17, 2018)

I just went downtown and spent $12 of the Rupnow fortune on a saw with a really radical tooth profile on one side. Tomorrow we will see about mounting it on the drag saw. I did find out something today. Saws that have a handle which spans both ends of the blade are only .024" thick. Saws that have a handle at only one end are .036" thick.


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## Ghosty (Sep 17, 2018)

Brian, that look like a good saw, I seen this at the hardware shop this morning, its only 9" long, but you found one.

Cheers


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## Brian Rupnow (Sep 18, 2018)

I installed the new saw blade, drilled a few cosmetic holes in the dog clutch handle, and put a very weak tension spring on the dog clutch handle to keep it disengaged. When it is engaged and the saw is moving, it seems to stay engaged without much of a problem, although I can disengage it quite easily by moving the lever. Even with the new aggressive sawblade, this thing is no speed demon at getting thru a log.  When you've been used to chainsaws all your life, this thing cuts pretty damned slow by comparison, but 100 years ago it certainly would have seemed like a marvel to two men on a manual crosscut saw. The batteries for my camera are charging right now, so I might get the final video up before the day is over.


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## Johno1958 (Sep 18, 2018)

Good job on the saw Brian. I agree how much of a marvel it must of been to the guy's on the cross cut saw back in the old days.
If I went back in time and landed on one of those two man cross saws I would give my self about 5 minutes before I was
huffin and puffin and whining about my back.
Cheers
John


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## whitehouse260 (Sep 19, 2018)

I wonder if adding a small amount of weight to the tip of the saw blade would help it cut faster?


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## Brian Rupnow (Sep 19, 2018)

Whitehouse250--yes, it would help a lot, however I am trying to maintain a profile similar to that of the old antique dragsaws from 100 years ago. I have two choices, it seems--add a weight to the arms, or find a log that saws easier. I just spent an hour and a half on the telephone trying to chase down a supplier of 3" diameter balsa wood, but had no luck. I did find a supplier of basswood, but they didn't know if it would saw easier than the spruce log I currently have or not.


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## BobsModels (Sep 19, 2018)

Brian

I have never seen a drag saw with a weight.  I have seen the Economy, Ottawa, and Witte.  When a teenager my grandfather cut wood for his furnace.  He would go out on my uncles farm and cut up fallen trees.  I helped and he had no power saws.  The larger diameter were cut with a two man saw.  He taught me that the saw did the cutting all we did was push - pull it.  If you tried to force down you buckled the blade.  It was just a nice see-saw motion and the teeth cut at a speed that was smooth.  Sometimes you actually had to hold the blade up a bit to get the cut to go.     The oaks, hickory,  and cherry were the worst.  The walnuts were like butter (probably why carvers and turners like it).  Butternut trees not too bad.  If you wanted to re-sharpen your blade try cutting an Osage Orange tree.  When I would use a cross buck saw it was the same thing no pressure.  So when I took up wood working and using a handsaw it was easy for me just let the saw work.

At the fair I mentioned the wood was real wet and he had to hold the blade up to try and get the cut going.

Bob


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## Brian Rupnow (Sep 19, 2018)

This will be my final video of the drag saw, and I am deeming it a success. It cuts logs the way it is supposed to, and the engine has ample power.


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## Brian Rupnow (Sep 19, 2018)

So--an interesting comparison. In the first video, using a newly sharpened carpenters saw, the saw took 7.2 minutes to cut thru the log. In the last video, with a much coarser style of saw profile, the saw took 3.2 minutes to cut thru the log. That is more than twice as fast.


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## velocette (Sep 19, 2018)

Brian Rupnow said:


> So--an interesting comparison. In the first video, using a newly sharpened carpenters saw, the saw took 7.2 minutes to cut thru the log. In the last video, with a much coarser style of saw profile, the saw took 3.2 minutes to cut thru the log. That is more than twice as fast.


Hi Brian another interesting project completed.
A dedicated cross cut saw doing a much better job of cutting and clearing wood fibres.
Eric


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## goody (Sep 19, 2018)

Nicely done Brian, the larger blade is more in line to scale with a full scale saw.    As I said the teeth on the Vaughn were 2” with a double cut profile so it cut on both strokes  the end of a single tooth had a W profile with both sides sharpened in between the wider W teeth was a V tooth I don’t remember the set on theV tooth but I think it was a raker it was slightly shorter.
WVWVWVW
Pat


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## Ghosty (Sep 19, 2018)

Brian,
Another top build, will be looking for your next build.
Cheers
Andrew


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## nel2lar (Sep 19, 2018)

Brian
The only reason the saw dust falls on the back of cut is because the final teeth bearied in the log has the sawdust captive in the tooth and the log will not drop until it is out of the log on the return stroke.
Beautiful, very nice job.
Nelson


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## CHIPWELDER (Sep 19, 2018)

Brian Rupnow said:


> I've spent 6 hours today in "geometry world", coming up with a set of linkages that will work for the drag saw. I know of no set of equations that will let you calculate this stuff. It is more "try it and see" engineering. What I have here is a set of linkages that go through all of the required motions without binding or going into a "lock" position. Now I have to take the time to do a visual comparison between what I have and what a real drag-saw looks like. This is fun stuff, but it isn't easy. Before I cut any metal, I will build these linkages full scale in cardboard and using "stick pins" work it through all of the required motions.


Mechanism Design vol 1 Arthur G. Erdman et al.  Ibuprofin can be sourced locally.  Isn't there a clutch showing in your photo? Possibly a small cone type?


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## Brian Rupnow (Sep 20, 2018)

Goody--believe it or not, the new blade is exactly the same size as the previous blade. The only difference is in the tooth profile.


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## goody (Sep 20, 2018)

But the tooth profile is more closely in scale with the tooth profile of a full size blade.

Pat


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## nel2lar (Sep 21, 2018)

Brian
One of your more interesting builds and enjoyed it all the way. The only thing it needs is a stop so the saw does not try to go to China.
Beautiful bild.
Nelson


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## Brian Rupnow (Sep 21, 2018)

Nelson--If you look really really close you can see a vertically oriented 1/4" bolt setting behind the top swing arm with the hex head on top. The swing arm can only go down that far. That is what prevents the saw from coming out in Peking.


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## SteveM (Oct 4, 2018)

Hello Brian
your drag drag saw is - like all your builds - interesting, beautifully engineered and innovative. I have (like I guess the silent majority) been watching with great interest and wouldn't normally comment.
Now I love your saw as it is, but I cannot help but think that it could be so much better with a different blade.  I've been cutting timber using handsaws in one guise or another for about 40 years, and I agree the modern saws usually have a cheap and cheerful look about them. But they are things of astonishing beauty when it comes to cutting timber! They outperform and outlast plain steel saws by miles. And they can be resharpened quite simply when eventually they fade. I'd be amazed if your machine couldn't slice through that log in less than a minute by using a weighted hardpoint toothed blade designed to cut on both push and pull strokes. Something like this (picture hopefully below).
I'd leave it as broad as could be accommodated to help with stiffness (), and in trimming it to length I would also make it long enough to add a weight to the tip; perhaps a pound or two of lead loosely secured so that it'll break free should it ever foul on the wood.
I hope that helps and it hasn't offended!
Best regards
Steve


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