Well now it’s offically silly season.. I’m tearing down the front of my house and want to double timber frame it as I did the back of my house. (hopefully somebody can find pictures of it in the archieves and post for those interested).
Anyway I want to build Black walnut posts.. They’ll be about 10 feet tall (plus base and top) and about 24 inch in diameter.. I’d use actual logs except for two things, the likelyhood of the logs checking badly and the early wood in black walnut isn’t decay resistant. (plus it’s white and won’t go well with all the rest of the outside timbers)
Thus I’ll need to turn my own columns. I’ve figured out how to glue up 4×4’s into a circle to make the rough blank and I’ve figured out how to build a cheap lathe using mostly scrap pieces and just a little fabricating, the only problem is that I don’t know what speed to turn the column. given that I should be able to figure out the pully sizes.
I’m assuming that I’ll start out with the glued up column about 26 inch at it’s maximum but when finished it should be around 24 inches..
Oh, and if anybody has a simple method of fluting the columns I’d like to know.. I had thought of using a router and a simple guide but that would make the base flutes much wider than the flutes at the top. I believe they are also supposed to taper in width to counteract the taper that the top has..
Replies
I would suggest 150 rpm max, with the low end around 100 rpm, but good luck, that will be a humongous lathe.
You must be getting your walnut almost free, were it me the columns would be hollow and segmented.
I've got stacks and stacks of 4x4 walnut, in fact so many that I build sawhorses out of them and use them as cribbage under more valuable wood. (I paid $2.00 each for them) and in spite of giving away over half of them Istill have too much..
(thus the frame work of my lath will be 4x4 black walnut)
You said 150 RPM was max with 100 RPM as the slowest you'd turn, I know this sounds like nit picking but I only want to buy one set of pulleys (they're about the only thing I'll have to buy, the rest is just a matter of fabrication and old stuff around the shop)
in fact so many that I build sawhorses out of them...
OH dang! And I just bought some walnut.. I think I'll go for a drink! Geeeeeeee....
set up a video camera the first time that you turn this home-made lathe that you are going to throw together and put a 1500 pound log on turning 100- 150 RPM's
Maybe you can get NORM and the TV crew out for that! It would be a CLASSIC show!
Ya made my day! LOL
Edited 4/29/2005 1:06 pm ET by Will George
Try making a roughing gouge out of scaffold pole tube while you are at it.Cutting the tube for a few inches lengthways makes a great roughing gougeand 6-8 feet long you have a serious mechanical advantage
Frenchy,
Do a search on huge columns, I have seen a site of a bloke doing this.
But.
The way fitters deal with this problem is to calculate the speed of the surface past the tool. (bearing in mind that I have not done this since '89 so please correct the algebra as you please and I'll try doing this in imperial measure)
I would rough a spindle down to 1" at about 540rpm if there was any chance of flex or instability.
1"* 3.14 * 540 = 1695 "/min past the tool
=> desired speed = 1695 / (diameter * 3.14)
<=> desired speed = 1695 / (26' * 3.14) = 20 rpm
This is still pretty scary, but we have all seen video at least of some very big table tops being turned at the 100-150 mark.
Have you considered building a router lathe? You would need two centres to fix the post an some sort of rail to run a router parallel to the axis. The post could turn at hand speed. The same setup would then be used to create your flutes.
Dave
Patto,
That's a thought, and no I hadn't thought about it. It would eleminate the motor (which I already have) and buying pulleys (which I don't) plus the complex bearing and squeeze assembly would be eliminated. There'd be a lot less fabrication involved and the issue of safery would be reduced to that of keeping the router on the guide system..
I like it!
This is a great site isn't it?
Frenchy, It doesn't matter if you have enough wood to give half away or not, you don't need to make life any more difficult than it needs to be.
Making them solid doesn't necessarily make them better nor easier.
I think it would be fun if you would set up a video camera the first time that you turn this home-made lathe that you are going to throw together and put a 1500 pound log on turning 100- 150 RPM's. Would you please look into the camera and grin real big. Maybe have James Taylor playing loud in the background " I'm a steam-roller baby, I'm going to roll all over you."
Your wife should be able to make enough money off of selling the video to buy a small island in the tropics with what she can get from selling that clip. I'll bet you might even make the Darwin Awards.
As Andy Warhol said, "We all get 15 minutes of fame before we are dead", so don't go out too fast now, I mean the saying would be wrong if your 15 minutes came after you were dead.
I did a little math for you. If your lathe gets this thing up to speed. It will have a peripheral speed of 680 ft. per min. Now you may be saying to yourself, " Hell I can run that fast", But just remember. You will be backing up, and there may be a wall back there somewhere, unless you have already torn it down. You know a wall would not be your friend about now. The more I think about it. How are you at the high jump?
Frenchy, I know it sounds like I am coming down pretty hard on you, but just the thought was too much fun to leave alone.
I will tell you how I would go about it later, if I were you. I think there is an easier way, but it is getting late, and you won't get this till tomorrow anyway.
How long does "Official silly season" last anyway? I would suspect whenever it is no longer -20 degrees out, it has to be a real blast for a couple of weeks anyway. Just remember. Try to slow down and take a few deep breaths every now and then. Too many of those little shallow panting short breaths will just throw you off. Later K
Rootburl,
I didn't intend to make them solid, I figure a cut at 22.5 degrees would give me an 8 sided column and I could cut a piece to plug into the ends.. Patto spoke about using a router over a hand pivoted post and it sure makes a lot of sense..
I can curve the guides to make the column have the proper curve into it and then use the guides to do flutes.. great idea.
I'm sorry if that means you won't get your video tape, or cheap laughs but your warnings didn't fall on deaf ears...
Edited 4/29/2005 10:46 am ET by frenchy
LOL,
That was funny, but honestly this can be done safely at 150rpm with an ordinary lathe chisel. The trick is to get either balance, or have a structure that takes care of the vibration.
The way to get rid of the vibration is building a raft with the logs first, with a wooden tail-stock and a head stock driven by a Mercury outboard engine. (You'll have variable speed also).
You do the turning in the middle of the lake, so the water absorbs the vibration through the raft and you don't pose any risk to nearby structures.
Also, I believe wet wood turns a lot easier.
The turned logs are tied with rope and pulled back to shore, you need a few extra logs, so the raft won't disappear underneath you, as you turn finished logs.
When I worked in Siberia, this was actually standard practice, only they used some Vodka as well.
Just don't drop your tools. Yours actually sounds like the voice of experience. Do you think I could do that in my pool instead?Do they have Mercury outboards in Siberia? I thought they just used skates.Andy"It seemed like a good idea at the time"
Hi Frenchy
I second Patto's suggestion that you make yourself a route lathe. You've enough "scraps" of lumber lying around the place to knock together a bench on which you could mount the rails. The latest FWW has the basic design for one, you just have to scale it up to your dimensions. The process will be a little slow, but fluting the resulting cylinder will be a cinch.
As to the column, you really only need a cylinder to carry the load, but laminating the 4x4s and getting a good glue joint along the entire length might be a challenge. I'll let another Knothead do the maths on the total clamping force needed, but I wont be surprised if it works out at a clamp every 4 inches or so.
The columns are on the outside so you will be useing a water proof adhesive wont you?
Ian
BTW 24in seems awfully big for a 10 ft long post
I agree with you and Patto. There's no reason in the world to try cutting these with a lathe chisel. With the router, the finish is independent (or very nearly independent) of the surface feet per minute of the wood, and you can turn the columns at one rpm, or two, or five, whatever suits your fancy.I think this approach also sometimes makes sense for other, more normal size projects, like long, thin balusters that tend to whip when turned at the nominally "correct" cutting speed.
Ian,
I'd planned on using strap clamps to hold everything to gether and I do happen to have a ton of them so every four inches isn't tough..
It's a big timber frame so 24 inches isn't going to be as large appearing as that, however you may have a valid point. I can easily scale it down if it seems wrong, at least using 4x4's will allow me to get the proper amount of taper without making the post too flimsy.
Darn I wish I could remember what that curve was called, the one that Greek columns have in them..
" Darn I wish I could remember what that curve was called, the one that Greek columns have in them.."Entasis.It helps accentuate the perspective of large columns viewed from the ground............
From Beautiful Skagit Co. Wa.
Dennis
Dennis,
Thanks I knew if I asked someone would have it!
Isn't this great site?
ps now I'm going to use that and claim full credit for knowledge (if I'm really feeling kind I'll give you credit ;-)
Now!the real challenge,who has the mathmatical formula to figure it out!!!
I don't claim any credit for the term, Frenchy. The Greeks came up with it even before ~I~ was born! (hahaha)As for the math, I can't help you any more with that. I had lots of diagrams and stuff in my old architectural history books but I've long since donated them to ...... sheesh, I even forgot who. (grin) All I can remember is that the curve is very subtle to the point that without it being pointed out, it's almost imperceptible............
From Beautiful Skagit Co. Wa.
Dennis
Now!the real challenge,who has the mathmatical formula to figure it out!!!
frenchy,
Get you a copy of Chippendale's "Gentleman and Cabinetmaker'sDirector". Dover #0-486-21601-2
The first few pages give a very good description of the various orders of Greek architecture, with explanations of proportions for the columns, amount and placement of entasis, etc..
Regards,
Ray
Ray
Frenchy
You need to generate 10 PSI (maybe a bit more or a bit less) on a glue joint to hold it together while the glue sets. You're face gluing 4x4s so your clamping force needs to be about 40 or 50 lbs per INCH of length. With clamps evey 4 inches this works out at 160-200 lbs of force in each clamp. I don't think strap clamps can do this. The type of joint you are using would normally be held together with G clamps or F clamps.
Ian
Ian,
I suspect that 160 pounds is easily in the range of the straps I plan on using, we hold equipment that weighs several thousand pounds in place on trailers with straps like these and I can really put a lot of "crank" into the straps.. In fact I remember once bending a 4x4 with just two straps.
well have fun. just make sure that the applied force is normal to the glue surface !
Frenchy, you don't need clamps. Drill pilot holes and screw the segments , remove the screws before turning. I would screw each segment first about a foot on center, remove screws and glue up. Then screw at each hole and add more screws if needed. The holes will be removed when you shave the mitered segments. Might be easier to plane the edges near the dimension you want before routing the taper.
mike
Mike, thanks for the tip, (I just read it) sounds like another great idea..
Knew guy who made commercial colums and made ####very low speed lathe with router to machine the colums. Think in terms of lathe duplicator with the router horizontal and a template to shape the column. That way you substitute a core box router bit for the flutes and all you do is change bits and router depth.
He was very successful as he understood the classical order of proportions in columns. The slight bulge 2/3's the way up is called "entasis" , so look that up to understand the bulge I'm referring to. Obviously you will be using epoxy so the clamping pressure isn't as great using other glues.
Can I ask WHAT the heck is want to 'double timber frame it' ?
Will George,
A double timber frame is one where there are timbers both inside and outside. Between I have SIP's to provide the insulation. You wind up with 18 inch thick walls but it's tremendously strong. (SIP's are approximately 200% stronger that stick built and when you add the strength of two sets of timbers together with the SIP's the numbers get really impressive)
Impressive as that sounds, I did it just because I like the looks...
150 RPM sounds about right.
Using the formula...(simplified) of Surface speed X 4/Diamter of work piece (or cutter - for flat stock)
I cheked SurfCAM and the surface speed for Mahogany is 1000 (feet per minute) and I can't imagine walnut is all that more or less...so 1000 x 4/24 gives you roughly 166 RPM.
I hope that is works for you, do be aware that the surface speed will be extremely fast (over 1000 feet per minute). Not to mention the force included with the amount of wood you are rotating, the inertia will be very large/strong.
You can find most of this information in the Machinist's Handbook or on the internet searching for cutting speed formulas.
Donkey
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