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Chevy in Plywood

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Blog entry by apprentice posted 05-18-2013 06:57 PM 1241 reads 0 times favorited 44 comments Add to Favorites Watch

After a play in 3D CAD here is my prototype Chevy in the making.

She consists of a single sheet of grade C birch plywood 18.00mm for the main body, trans arms and internal levers, seat etc, and there is still a couple of square feet left over after all the parts were cut out.

So far the cost of materials comes to just under a hundred pounds for 99% of the materials, the plywood was £40.00 inclusive of tax. All the main sections were cut out acurately for me at the supplier at no extra cost.

I’m making the head unit similar to the traditional but slightly different, so it can be made without complicated joints for those like me without any planer/thicknesser or saw bench. I’m using a router and a bandsaw for the majority of the work, and I have opted for hand cut dovetails for the construction.

Picture above shows the one piece plywood body with the two halves split to show the internals.

The internals consist of two nylon pulleys an bicycle chain and an upholstery spring and three sections of 25.00mm aluminium tube which passes through the body and secured by a pair of R clips on each shaft for easy removal. I turned the pulleys by hand on the wood lathe to take the chain.

The chain travels from the middle of the vice/jaw, around the pulleys to the multi layer foot pedal and arm on the bottom.

Showing the spring sat in its groove to prevent it from wandering during operation.

The vice/jaw opens opposite to traditional Chevy’s, which opens when you depress the pedals with your heels, the vice holds the work nice and firm once you stop cutting, you can let go when you stop cutting.

The main transarm is fitted and passes right through the main body and its secured by a wooden cam to quickly lock up the arm itself, next post will show the arms made from plywood and dovetailed together.

More soon.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded



44 comments so far

View shipwright's profile

shipwright

5010 posts in 1464 days


#1 posted 05-19-2013 04:00 AM

This is interesting. You are making a lot of changes from the time honored construction.
Please don’t take this as criticism, just an observation.
I hope it works out for you.
Can you show us an overview to better understand how these parts relate?

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Jim Rowe's profile

Jim Rowe

561 posts in 979 days


#2 posted 05-19-2013 07:38 AM

Davy
Looking forward to seeing further shots. Was the laser cutting done for free? Will there be enough ooomph in the upholstery spring to hold the jaws of the vice closed tight enough when cutting?
Jim

-- It always looks better when it's finished!

View apprentice's profile

apprentice

201 posts in 826 days


#3 posted 05-19-2013 09:33 AM

Paul

Not at all, I welcome hints and tip from anyone, sometimes it takes criticism to jolt the memory into being. There are several similarities to the traditional Chevy which is basically a vice, the way I aproached things is from an engineering problem solving angle, to the final mechanisms I opted for.

As I put everything together things will become clearer as to how everything sits, its still in the prototype stages and I have seen a couple of mods already. The main aim in this model is price versus minimal tooling, so everyone with woodworking skills can obtain a Chevy for under a £100.00.

Jim

The spring is strong enough to clamp things tight and aided by a floating/pivotting axle which pushes paralell to the facing jaw, holding an area 3 circular inches and pinpointing the very centre, allowing for the compression of the pack, the jaw can also turn and has six cutting avenues.
As the operator is cutting they are using energy to keep the jaws closed, this is where the spring takes the load instead of the legs, release is instant with a press of the heels, saving energy overall.
The other donkey version has other qualities for very detailed work as it lays horizontal, and I will be doing a full test once both Chevy’s are up and running.

The cutting was done on the wall saw not CNC, I worked out that I could cut out and drill all the waster using a router in the same time as the machine, there is very little in it, and I’m 50 quid up.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View apprentice's profile

apprentice

201 posts in 826 days


#4 posted 05-19-2013 04:12 PM

A couple more shots of the side plate, this time with the trans arm hole cut out so you can see where in fits in relation to the main body, it passes through both sides and is secured by a concentric locking cam and lever not shown, when I get nearer I will show more.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View apprentice's profile

apprentice

201 posts in 826 days


#5 posted 05-20-2013 07:32 PM

A little further along the build, the main carcas is now jointed together and secured using screws so it can be dismantled at any time. The front leg is fitted and is also detachable via two bolts that anchor to the lower foot pedal pivot and running through the aluminium tube, pictures tomorrow.

The vice is now tuned and holding very firm, tomorrow I will fit the seat which will incorporate a tool box underneath it for all your spare blades etc.

Here is how I do the dovetails really quickly, first mark them out and handsaw the down angle cuts, then place a prepared straight squared piece of hardwood on the line and either side and clamp them using some Facom quick release claw grips, then with the aid of a Fein Multimaster, rest the standard holtz blade on the hardwood supports flat surface and gently cut out the block for removal, once you get used to handling this kit you can make good fitting joints like shelling peas.

I dares to say, not even Mr Cosman could do these joints in plywood that quick.

Checking the trans arm socket for plumb, spot on hole to hole which was cut in as a pair to make sure it was exactly the same, so good so far.

Tomorrow I will fit the seat and make the locking cam.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View shipwright's profile

shipwright

5010 posts in 1464 days


#6 posted 05-20-2013 08:57 PM

It will be interesting to see how the reverse clamp works in comparison to the original.
In my mind it will require more effort and will give you less precise control than the original as you will always be pressing to release some of the spring pressure. Sometimes you need strong pressure so the spring must be able to supply that but most of the time very light pressure is used.
In the original the pressure exerted by your heels is not much at all and you hardly notice it but when you need more pressure, it’s easy to apply a lot.
The plywood construction part seems reasonable . My reservations are about the clamp.

I’ll be interested to see your results.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View apprentice's profile

apprentice

201 posts in 826 days


#7 posted 05-20-2013 09:25 PM

Hi Paul

I have allowed for the pressure scenario by making the fulcrum easy to use, very little pressure is needed to release the vice, like covering the brakes in your car, slowing but not stopping, the secret is in the jaw design, the pack can be gently guided against the rear flat platform and large surface area there acting as a huge dampening device., this platform also prevents any winding of the pack, similar to the flat platform on my other Chevy.

The whole system acts like a clutch so the pack can be moved about with the controlling hand, under dampened conditions, never allowing it to fall out of your hands if you forgot to press the pedal on the conventional version, putting pressure on the blade possibly breaking it.

There are many ways to skin a cat, using 3D CAD, learning the mechanics and physics of engineering first helps a great deal, the challenge is getting everything to work but in a different way.

I do not intend this to become a competition Paul, mearly a personal engineering challenge, that’s all, if it fails, I can simply copy what has already been done before.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View shipwright's profile

shipwright

5010 posts in 1464 days


#8 posted 05-20-2013 11:28 PM

Good for you for re-inventing the wheel.
It’s my favorite pastime.
After all, there’s a lot more room to breathe and think once you get outside the box.
I don’t see any competition here at all, I’m just curious how it will work out and passing along my thoughts.
Keep us posted. This is really interesting.
You should post a link to this at the chevalet clubhouse.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Mathew Nedeljko's profile

Mathew Nedeljko

607 posts in 2496 days


#9 posted 05-21-2013 03:00 AM

Apprentice, I’m interested and following along too. The concept of a reverse vise that is normally closed vs normally open is an interesting idea and an engineering problem that is worthy of exploration. Best of luck to you in sorting it out!

-- Aim high. Ride easy. Trust God. Neale Donald Walsch

View apprentice's profile

apprentice

201 posts in 826 days


#10 posted 05-21-2013 06:24 AM

Like all challenges it must first be chewed swallowed and digested, then tested, and why the box and its birthing pains are shared as it passes. Being in view has already brought out some answers from others as to a possible future rectifcation.

It is not yet worthy for the clubhouse.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View apprentice's profile

apprentice

201 posts in 826 days


#11 posted 05-21-2013 01:51 PM

Picture a 9 gauge upholstry spring doing Mach 2 through the air into the undergrowth, only kidding.

The spring affair was strong enough and easy enough to relaese, BUT, way toooo, sensitive to control, it was simply very frustrating to operate.

Picture the working solution, still back to front but lots easier to operate and much more powerful, seen set up outside the main body for display.

Hands up, lessons learned and moved on.


More coming soon, comments please.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View helluvawreck's profile

helluvawreck

15904 posts in 1533 days


#12 posted 05-21-2013 02:12 PM

This is really interesting. You must be putting a lot of work in this.

helluvawreck aka Charles
http://woodworkingexpo.wordpress.com

-- If a man does not keep pace with his companions, perhaps it is because he hears a different drummer. Let him step to the music which he hears, however measured or far away. Henry David Thoreau

View apprentice's profile

apprentice

201 posts in 826 days


#13 posted 05-21-2013 04:23 PM

A couple more shots of the front cross leg and fastening mech so it fan be removed and the pivot tube retaining clips, ane the guts in situ.

Starting to look like Chevy worthy of the clubuouse, 25 full hours work so far.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

View shipwright's profile

shipwright

5010 posts in 1464 days


#14 posted 05-21-2013 04:53 PM

Looking very interesting.
I think changing to foot pressure adding force rather than reducing force is a good move and will improve control.
I like the plywood construction from an engineering standpoint (see my workbench) but you’ll have to veneer it (maybe a little marquetry) to make it look as nice as a solid wood one.
Do post in the clubhouse, I think you’ll get more feedback.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View apprentice's profile

apprentice

201 posts in 826 days


#15 posted 05-21-2013 06:56 PM

I really like the bench, bookmarked it when you first put her on show, I will eventually make something, with vices that close conventially, hehe.

Veneering the Chevy is out of my price range I’m afraid, I will give here a good filling in of the marks left by the router guides/screw holes and a nice coat of paint we have spare.

My main target was a Chevy for a 100 quid or less and that’s my limit, and I have done it price wise with four square feet of board left over.
When its fully done I will post up the DXF’s so others can get the superstructure CNC’d.

-- http://www.youtube.com/watch?v=qcyhgsGA6mY&feature=player_embedded

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