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Moravian Bench Reimagined #4: Which Bench, Part 2

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Blog entry by MagicalMichael posted 10-08-2019 04:06 PM 304 reads 0 times favorited 2 comments Add to Favorites Watch
« Part 3: Build Which Bench Part 4 of Moravian Bench Reimagined series Part 5: Over and Under Planning »

So,…. at this point I had decided on a split top Roubo with an HNT Gordon face vice in place of the classic leg vice. I was still undecided about the tail vice except that I had finally ruled out a traditional tail vice in favor of a wagon vice. The romantic in me favored the Lake Erie (L.E.), the accountant favored the Hovarter, and the perfectionist favored the Benchcrafted (BC.) As I continued to study these alternatives it finally dawned on me that my unacknowledged criteria included ease of installation and completing this project in a modest amount of time. I did not want to spend a whole winter building this bench while many other projects percolated in my imagination, and of course the set of nesting tables my wife had requested on multiple occasions. The L.E. installation instructions seemed straight forward enough but suggested a very high degree of accuracy, much like my leg vice. The Benchcrafted (B.C.) seemed a bit easier. The Hovarter seemed easiest of all, but required a very big – 150 -175mm end cap securely anchored. I didn’t like the way that would look on a Roubo Bench and I didn’t like that it doesn’t work in reverse to use as a spreader. Not an absolute deal breaker but… I finally settled on the BC and dove into the details of the build.

Three things displeased me. One percolated just at the edge of consciousness; one in the realm of denial; and one in the minutia. This split top roubo bench was going to take a long time to build; this bench used a huge amount of material; this bench required either humongous through mortises into the top with exposed end grain, or lag screws into the top,neither of those appealed to me. You may remember that my current bench’s fatal failure was with lag screws. So I searched for a third way and posted for suggestions on the Work Bench Smackdown Forum. That created a turning point.

Someone, (Jeff ?) suggested, given my concerns and priorities (I may be moving in a year or two and at 75 I could envision the bench being transported 3,000 miles to my son’s home in California. and so wanted a bench that could be disassembled) that I should be building a Moravian bench. In all of my research I had never more than brushed up against this design. It is not mentioned in either the Lewis or Schwartz books. I’m sure I had seen pictures, probably on the L.E. website, but had always thought of it as an oddity, an evolutionary dead end. It looked strange. Perhaps not as strange as a Nicholson but still strange looking to me.

As you may have guessed by know, I am trained as a corporate planner. I analyze and analyze and analyze. But not always. Almost 30 years ago, not many years after building my current Scandinavian Bench, I picked up a trifold from a seminary in Indiana describing their program to prepare people for chaplaincy in prisons and hospitals. I immediately decided to become a prison chaplain, where I was currently offering three day, intensive, experiential workshops on conflict resolution. I eventually became a hospital chaplain, but that’s another long story. Something similar happened here. After about a week, I discarded nearly three years of study, abandoned the Roubo and decided to build a modern reinterpretation of the classic Moravian bench.

As I got past my prejudice against this odd looking design, and my fixation on right angles, its virtues began to appeal to me. The triangulation (yes it looks like a trapazoid but the joinery creates triangles) creates a bench with great rigidity while using about 1/3 less material and requiring less time to build than the Roubo. The frame is more compact and the top, 75mm instead of 100mm, attaches with simple pins, instead of through mortises or lag screws. Having it easily break down is just the icing on the cake.

Swapping out a leg vice for the Gordon face vice simplified construction considerably, but reopened the question of how to incorporate a tail vice. My prior decision, the BC, requires a 100 MM top. I was not enthusaistic. Now I know there is a widespread believe that a bench needs to weigh 400+ lbs to be stable and rigid. My Scandinavian, which doesn’t way anything near that is quite stable and has as much weight as I want to wiggle around my shop. I went back to looking at the Hovarter, which can be easily installed on 75 mm top but would then require a 120 MM end cap securely fastened to the top. Also, it doesn’t work in reverse, so it can’t be used to spread open joints. Not too big a deal, but… I finally came back to the Gordon tail vice. It is ultra simple to install, offers plenty of clamping power and because it attaches directly to the top doesn’t require a locked-down end cap. Yes it is slow, but so am I, and have decided to live with that limitation. Slowing down isn’t all bad.

I have never been good at coloring between the lines, so right away, having seen the advantages of the Moravian bench design I began to ask why this and why that. Unconsciously I set out to use the traditional design as the foundation for something that incorporated my personal needs.

The first question that came to mind was why are there three rails, each with a different joint when all other benches have either two, or just one and rely on the top itself for horizontal stability? My first response to that was to note that the upper rail with a saddle joint offered great vertical strength but lacked horizontal strength apart from any pins that might be added. Since it was a saddle joint in my Scandinavian bench that first created a problem, I was immediatly concerned. At that point I assumed that the middle rail, set high with a classic through mortise and tenon joint was there to create the horizontal rigidity which the saddle joint lacked. As my research unfolded I noticed three things, which after a few weeks (those summer house repair projects did give me time to think about the bench design.) First, I noticed that the original model did not have the middle rail on the right hand side. Then I focused in on the dimensions of the long stretcher. The Myers Bench has ultra beefy stretchers that are 3 1/2 X 2 3/4. I wondered why the design required such a massive stretcher. It wants 1 1/8 or so for the tusk tenon but then 2 1/8 would be plenty wide enough. Finally it dawned on me that all of this joinery was designed to stabalize the force of the leg vice against both the rail and top joint. The middle rail frames an opening for the screw to go through and the bottom stretcher is fat enough to resist flexing under the load.

Since I would not be adding the leg vice I didn’t need to worry as much about the forces on the leg and stretcher. My first thought was to beef up the top joint and then eliminate the midddle rail all together. Then I thought I might add it simply as a lift point for when I wante to move the bench this way or that a foot or two. That’s about where I was when I set off to Tree House Hardwoods to buy the rough lumber for this bench.

At this point lots of planning went out the window, but I’ll leave that tale for another day.

Here’s what it looked like, stacked up and ready for the dance.

-- michael



2 comments so far

View Sylvain's profile

Sylvain

881 posts in 3012 days


#1 posted 10-09-2019 07:59 AM

- “I noticed that the original model did not have the middle rail on the right hand side.”
Interesting. It had escaped me.

- With the vertical leg vise, there is no clamping effort in the leg. The only effort is between the vise backer-board’ stub tenon and the top (via a groove in the top)
It is not the same with the angled leg vise version. In that case, the leg serves as backer board and the pin must resist to the clamping effort.

- the workbench rigidity and the strength of the joint long-strecher/ leg-frame relies on the tenon shoulders. So it would be good practice to have the strechers 3 X 1”1/8. Especially with the required loose fit, I would not make narrow tenon shoulders. Now if you think the 3”3/8 is not needed for the whole length of the strechers, you might try to beef up the strechers only where they meet the leg-frames.

-- Sylvain, Brussels, Belgium, Europe - The more I learn, the more there is to learn

View MagicalMichael's profile

MagicalMichael

150 posts in 1029 days


#2 posted 10-09-2019 04:13 PM

Thanks for that clarification. I completely agree with you. I had not even thought about the angled vise. It seems to me that the vertical leg vise will exert a consierable amount of pressure on the stretcher, which will get transferred to the leg and on the top, where it will get transferred to the bridle joint. However, since I am using a Gordon Face Vise (see my earlier blog post) I don’t feel I need to worry about that. 54 mm stretchers will be plenty strong enough to hold the end frames rigidly in place and two sturdy rails will hold the end frames.

Michael

-- michael

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