Model Sawmill Dreaming---

[Jasonb]

Brian you don't need a gear cutter to do ratchet wheels, a standard end mill will do the job, just set it so the edge of the cutter is on centre line or the ratchet wheel. Or for a better undercut a simple singel point tool can be made like a fly cutter.

I have done a few for the tarchet lubricators on traction engines, each stroke of the valve rod gives about 1/40 to 1/60 of a turn to teh pump ram.

A #1 cutter in any DP will cut the correct profile for a straight rack, you may have to make it in sections if you don't have ahorz. mill.

J

 

[Noitoen]

To back the carriage, they may use the flat part of the ratchet wheel. It's difficult to see if there's a flat belt or not.

 

[Jasonb]

I would say the four handled spider in front of the ratchet wheel is used to manulally bring the log upto the start of the cut and then wind it back for the next cut. Lift the wooden handle that you can see moving up & down to disengage the ratchet

J

 

[johnmcc69]

Hi Brian,
You may want to check out the SDP Stirling instruments
Catalog web site, I see they have a nice selection of
Racks in lengths up to 18". You may be able to find
something in a suitable scale. They also have CAD
models available.

Looking forward to your design & build on this!

John

 

[Brian Rupnow]

I'm still tossing this sawmill idea around in my head. After prowling around on a dozen "Muley" type sawmill videos, I have a pretty good idea of what I will design. One thing of note, is that these sawmills which cut with intermittant strokes generally incorporated a good sized flywheel somewhere in the system.The kinetic energy "stored" in the rotating flywheel during the "non cutting" part of the cycle would be released during the "cutting stroke" and help keep the waterwheel from bogging down. ----And if it worked for waterwheels, the same technology will work with small hit and miss engines. A number of people who have actually built similar model sawmills have told me that the small engines bog down badly during the cutting stroke combined with the foreward movement of the carriage and log. I have an idea of how I might address the issue. Since the foreward motion of the carriage is initiated by an eccentric which drives the ratchet and paul, it would probably be a really good idea to have an adjustable eccentric. This would allow you to "dial in" the amount of carriage advance during the cutting stroke of the sawblade. My next idea, and it may be a good one, is why use a ratchet and paul if there is something better. The "something better" in this case would be a "one way bearing" ---see attached link. If the outer race of the bearing was Loctited into a peice of round stock, and the inner race atached to the pinion shaft which drives the rack on the carriage, then the arm from the eccentric could just rock the roundstock back and forth and the bearing would only transmit rotary motion to the pinion shaft in one direction. The "arm" could be a quick disconnect from the roundstock to enable returning the carriage to its home position after a cut was made.
http://www.onewaybearings.com/

 

[Brian Rupnow]

Well, I guess I have to start somewhere!! For my sawblade I have settled on a good old garden variety hacksaw blade. They are available in many different tooth configurations and only have about a .055 kerf. I can cut them to whatever length I want.--For a sense of scale, it measures 4 1/2" between the vertical arms on each side. I have only guessed at the length right now. You will see I have placed 1/8" wide "wheels" in the vertical uprights to cut down on friction with the guides when the log is being fed into the saw.

 

[Brian Rupnow]

Enough of this foolishness this morning!!! Its a beautifull day out and I'm not going to set inside for the rest of the day designing.

 

[Brian Rupnow]

Something like this---

 

[Jasonb]

The con rod looks quite short, a slightly longer one would put less sideways load onto the frame and give a smoother running saw.

J

 

[Brian Rupnow]

Good Lord!!! What have I gotten myself into here???

 

[Brian Rupnow]

Well, with the exception of the incrementing drive parts for the carriage, there it is, mostly designed. I will probably shorten up the carriage a bit, and consequently the overall length will come down about 1 1/2". In theory, it will work. Its almost impossible to know how much power it will take to drive it. I will finish up the incrementing drive tomorrow.

 

[starnovice]

Brian,
I have just finished reading all of your threads. I feel like I have known you for about 4 years. You have done some really great work and have taught me a lot. I can't wait to see this sawmill completed.

th_wav

Pat

 

[Herbiev]

Looking great Brian. Cant wait to follow the build.

 

[Brian Rupnow]

Thanks guys, I appreciate your comments. When I do this sort of thing everyday, all day, it doesn't seem like such a big deal to me. I always get such a big thrill when I know that others are watching and commenting as I go along. I will be posting the plans as I go through this, as I usually do.----Brian

 

[bret4]

Looks like a fun project. I know when I made my first engine a long time back a young person said "so what does it do?" This looks like something that the younger generation would find more interesting to watch when run by a steam engine.

 

[Tin Falcon]

Well Brian what can I say. It seems like within a few hours you go from a dream and pondering to a near complete set of plans. I guess that is what happens when you have 20 plus years experience as a designer. I can draw parts fairly well on alibre but still having a time assembling stuff. practice practice I guess.
thank for sharing.

I have seen a few model saw mills , drag saws etc at cabin fever but do not recall seeing one like this good work.
Tin

 

[Brian Rupnow]

This is a view of the sawmill with the adjustable eccentric, linkage, and one way bearing which will advance the carriage and log into the saw blade. Also a blow up of the adjustable eccentric area. I still have to design a method for "quickly unlatching" the linkage to allow the carriage to return to the other end once the log has been sawed.

 

[Brian Rupnow]

Tin---Try 47 years plus!!! I started this foolishness (designing machinery) in July of 1965.--And that is all I've worked at my whole life.---Brian

 

[johnmcc69]

Looking good Brian. Which of your
engines will be powering this?

John

 

[Brian Rupnow]

Looking good Brian. Which of your
engines will be powering this?

John

Right now I'm thinking the Kerzel hit and miss.