Tandy Stitching Pony Modification...

[Martyn]

Been using a couple of bits of wood as a clamp for ages, but I finally bit the bullet on a Tandy original pony when they had some on half price sale.

This one...

I was a bit disappointed though. The wingnut thing seemed a bit crude for the price and it spun - why couldn't they put a washer on it? Also, I wasn't keen on using the wooden block thing to open the clamp up ....and there seemed to be an awful lot of spring in the legs - it really didn't need a wingnut to keep it closed. So I started thinking what could I do to make it into the pony I was hoping it was going to be.

here it is in it's tarted up glory...

...mostly cosmetic. I added a couple of magnets up top, a holster for my pliers, shaped and shortened the leg and added a 'saddle', but the real functional mod and what I wanted to share, was what I did to the tensioning system.

As you can see I removed the bolt and wingnut and replaced it with a cam-clamp and spring system...

Much, much easier to use the cam-clamp than the wingnut, but the main addition that I havent seen before is the die compression spring. The spring works against the natural spring of the clamp and is in balance. Finding the right spring was tricky, but this is bang on. If I open the clamp up fully, the jaws open to about 3/4 of an inch under the force of the spring. At that point, the spring runs out of 'juice' fighting the clamp. I can open it up to about an inch and a quarter, but the spring needs a little help. But for everything I've done to date, 3/4 of an inch has been more than enough. I lift the lever, unwind, insert project, wind in the desired tension it's just a question of opening and closing the lever to move and re-clamp. You can set the clamping force to be like the brush of a butterflies wing, or about 200lbs and anything in between. That adjustment works exactly the same, regardless of the thickness of the project (up to the 3/4 inch mentioned, after that, the clamp starts to beat the spring a little). Overall, I'm super happy.

The little leather shield under the handle acts as a thread deflector, basically stops your thread from getting hooked under the arm of the clamp.

Clamp open...

closed...

Works like a charm. I'm sure I'm not the first to combine a compression spring with a cam clamp like this, but I havent seen it before so I thought I'd share. If someone has a Tandy pony and they fancy doing this mod, I can dig out the exact hardware specs I use, which would save some legwork. LMK if it's required.

Cheers,

Martyn.

Edited March 8, 2016 by Martyn

[Tugadude]

Nice job! Yes, share details for others to benefit from. Much appreciated.

[Martyn]

OK.

The cam clamp is the 'Cam Action Hold Down Clamp' from Wood River. They do 2 versions, a 1/4" version and a 5/16" version. Get the 5/16" version. I think it's $7.99 on Amazon (it was about £10 in the UK but I cant remember where from).

The clamp comes with a 3 1/2" bolt with a 'tee' head. It's not long enough. So you will need to replace with a 4 1/4" long x 5/16" dia bolt with a UNC thread (18 tpi) - make sure to get the right thread type. It's not critical, but as a spring is running over the shaft of the bolt, a part-threaded bolt is preferable. I think mine has the last 1 1/2" threaded and it's perfect.

You will also need 4 steel penny washers, 5/16" hole, 1" OD and 4 rubber washers of the same size also.

The spring was from Hong Kong via Ebay.uk and was £2.45. It was listed as...

16mm x 8mm x 65mm Spiral Chromium Alloy Steel Stamping Compression Die Spring

...but I just did a search for die compression spring. You'll get 100's of hits. The dimensions are important, 16mm outside diameter, 8mm inside diameter (runs nicely over 5/16" bolt) and 65mm long. This will give a neutral tension point with the jaws open about 3/14". The colour of the spring is also important as they are colour coded for their duty rating. Yellow is classed as light duty. If you are trying to buy from ebay.com (rather than ebay.uk) you'll probably have to convert the metric dimensions to imperial to find the right spring in the listings.

That's it. Assemble when the bits arrive so it looks like the pics above. I just levered the spring in-between the legs of the clamp, using the block to jemmy open the legs a little. It's a bit of a fight, but it's doable and no need to disassemble the clamp or anything (it's actually glued up anyway, so attempting disassembly would probably damage it).

total cost is probably a shade under $15 US.

Actually, when I think about it, Tandy should build em like this for the price they are selling them for. I bet with Tandy's buying power, they could source the parts for under $5 dollars.

Edited March 8, 2016 by Martyn

[Studio-N]

very nice modification. thanks for sharing.

[Martyn]

very nice modification. thanks for sharing.

You're welcome. I probably should do a video showing the function, because pictures dont really tell the story. The mod radically alters the way the clamp operates. It's now fully spring loaded, balanced, super quick, one handed (actually one-fingered) operation with both coarse and sensitive adjustment through a good range of movement.

[mikekratz]

fantastic modification! thanks for sharing!!

[Martyn]

I made this video in response to another thread, but I thought I'd add it here too as it illustrates the operation of the pony once modified...

 

[sideforce]

Nicely done!  Thank you for sharing.

 

[wayner]

parts are on Amazon 

CAM ACTION HOLD DOWN CLAMP - 5/16" X 18 TPI by Peachtree Woodworking - PW965

 

Red Medium Load Press Mould Compression Die Spring 16mm x 8mm x 65mm

 

[bkemp]

Really like this modification! Thanks for sharing in detail! 

Can anyone tell me the inside measurement of 2 clamp arms or the block at the bottom on this specific pony?

I made a homemade pony and would like to add the spring. What I really need to know is how much longer the spring is than the gap between the arms. I can calculate this once I know the space. 

[Martyn]

5 hours ago, bkemp said:

Really like this modification! Thanks for sharing in detail! 

Can anyone tell me the inside measurement of 2 clamp arms or the block at the bottom on this specific pony?

I made a homemade pony and would like to add the spring. What I really need to know is how much longer the spring is than the gap between the arms. I can calculate this once I know the space. 

The gap is...

Fully closed: 56mm,  fully open: 60mm - and the inside washers (1x steel penny washer + 1x rubber penny washer) are 4mm each side. But remember, the legs on a Tandy clamp are in a state of compression, so are squeezing on the spring at all times. So the 65mm spring is about 48mm fully compressed and about 52mm with the clamp fully open. That 4mm of movement in the spring, creates about 22mm of 'range' at the jaws. The jaws will open wider than that but need a little manual assistance. I was limited because the legs of the clamp are glued in place and I didn't want to risk breaking them by trying to force in a longer spring. But if I was doing it again, I'd probably try and carefully take one of the legs off and install a 70mm spring just to give it a little more range - though I haven't actually needed more so far.

Oh and the centre line of the spring is 185mm below the very top of the jaws.

Go with the yellow 'light duty' springs. They are plenty strong enough.

 

Edited November 10, 2016 by Martyn

[bkemp]

3 hours ago, Martyn said:

The gap is...

Fully closed: 56mm,  fully open: 60mm - and the inside washers (1x steel penny washer + 1x rubber penny washer) are 4mm each side. But remember, the legs on a Tandy clamp are in a state of compression, so are squeezing on the spring at all times. So the 65mm spring is about 48mm fully compressed and about 52mm with the clamp fully open. That 4mm of movement in the spring, creates about 22mm of 'range' at the jaws. The jaws will open wider than that but need a little manual assistance. I was limited because the legs of the clamp are glued in place and I didn't want to risk breaking them by trying to force in a longer spring. But if I was doing it again, I'd probably try and carefully take one of the legs off and install a 70mm spring just to give it a little more range - though I haven't actually needed more so far.

Oh and the centre line of the spring is 185mm below the very top of the jaws.

Go with the yellow 'light duty' springs. They are plenty strong enough.

 

Thanks for getting those measurements!  Just for clarity, the gap is 60mm with no tension? If not, could you please measure the block between the arms at the bottom? That would get the measurement with no tension. 

 

The measurements on mine like it sits: 38mm no tension. 32mm closed. 

I am looking at the yellow spring that is 16x8x45mm. Thoughts? 

[Martyn]

1 hour ago, bkemp said:

Thanks for getting those measurements!  Just for clarity, the gap is 60mm with no tension?

Correct. But like I said, the Tandy pony has clamping tension in the limbs, they are not parallell and the block at the bottom is not square, but a slight wedge. If I remove all the hardware, the top of the block is 58mm and the jaws are clamped together. It's actually perfectly usable without the bolt and wingnut. If you watch this video of an unmodified Tandy Pony, you'll see what I mean:

 

1 hour ago, bkemp said:

The measurements on mine like it sits: 38mm no tension. 32mm closed. 

I am looking at the yellow spring that is 16x8x45mm. Thoughts?

Yeah, that sounds about right. You have to remember you'll add some with the washers. It also depends how far down you put the clamp, but yeas, sounds about right. It depends how wide you want the jaws to open under the force of the spring. It looks like a 45mm spring will open them to a little past neutral, but that is just an educated guess.

Edited November 10, 2016 by Martyn

[bkemp]

Ahh,  that makes sense how it can be closed and pressure applied so easily. I may be modifying my block with a wedge or take 1/2" out if it's too difficult to get it clamped. 

The clamp position is nearly identical to yours. 

Thanks again for you help! 

[Martyn]

I'd try it as-is first, you shouldn't have any problem clamping it, I think the clamps are rated for about 200lbs or something ridiculous. The cam puts a helluva lot of force through the limbs. If anything, I think yours may work better. In fact, you may not need a spring at all.

Edited November 10, 2016 by Martyn

[AndyL1]

Excellent mod! I think I found the spring on Amazon:

 

https://www.amazon.com/16mmx65mm-Chromium-Lightest-Spring-Yellow/dp/B018RSYE08/ref=sr_1_1?ie=UTF8&qid=1478827802&sr=8-1&keywords=16mm+x+8mm+x+65mm+Spiral+Chromium+Alloy+Steel+Stamping+Compression+Die+Spring

Thanks for sharing this. I already order the clamp.

[Martyn]

6 hours ago, AndyL1 said:

Excellent mod! I think I found the spring on Amazon:

Yep, that's the one I used.