1/16 Scale FrankenDiff

[ddmckee54]

OK, as promised we'll open up the picture page. (Who besides me still remembers the jingle for Picture Pages?)

What you're looking at is the view from the passenger side, standing in front of the center axle looking to the rear.

I've temporarily hidden the passenger side frame rail, and just about every part of the suspension is in place now. I don't know how many leaves I will need for support, that's why there's a gap between the springs and the equalizer beam pivot bracket. I've got the springs drawn as three 0.5mm thick leaves, that may, or may not be overkill. I'll adjust the amount of leaves to suit the load, for now I'll probably just make a spacer block.

I'm still waiting for the donor axle order, according to the tracking it should be here within the next week. I sounds like the O-rings, the brass tubing, my 8" caliper, and the other odds and ends that I ordered should all get here about the same time.

Don

[Zabco]

Cool ideas, will be very interesting to see how they work out.

[ddmckee54]

I had a brain fart a little while ago, I came up with a way to bend 2mm U-bolts for the springs using 3D printed dies. Right now it's just a paper sketch. Tomorrow, I'll get it in CAD and print the dies out to see if my idea will work.

Don

[Zabco]

Several years ago I made some benders out of steel to make various types of u-bolts. Was a lot of work to make them. Squared, round, different lengths, different rod sizes, etc. I will be very curious to see how printed dies work out. May have wasted a lot of time.

Don't forget, you have to thread the ends of the rods BEFORE you bend them. Can probably guess how I learned that one.

[ddmckee54]

Well, the first attempt was an outstanding failure, which was not unexpected. It produced a rounded, sorta U-shaped object - whose legs were within a millimeter of being equal. However, I was TRYING to produce a squared off U-bolt with corners of a much tighter radius.

It was a bad die design on my part. I was afraid my movable die would allow the 2mm rod to move around.... It took the easy way out and moved. I didn't have nearly enough perimeter walls or infill either, 3 top layers, 3 bottom layers, 3 perimeter walls, and 30% infill didn't cut the mustard.

I'll double all of those on the next test, I'll also change the design of the top die. I want to restrict the rod so that it can't flex away from the top die like it did on the first test. According to the slicer, doing that will increase the print time for the dies by about 50%. Which will make it about 1-1/2 hours to print, and that's still not bad at all.

I'm only using PLA for the dies. If it doesn't look like that can take the stress, I can easily see modifications to the dies to allow the high-stress parts to be made of steel. (Or at least put steel in the high stress areas.)
Don

[ddmckee54]

OK, the second verse is ALMOST a repeat of the first, and I've got pictures to prove it.

This is the parts of the first die.

The movable top die is on the left and the base die is on the right. That V-for-victory shaped thing in the middle is the result of the first pressing - IT won. I'm using a Harbor Freight 1/2 ton arbor press to do all the pressing.

This just shows how things went together for the first press.


I modified the base die and the top die for the second attempt. The first dies only had 3 bottom layers, 3 top layers, 3 perimeter walls, and 30% infill - I doubled all of those for the second attempt. The areas that had the most damage on the first dies were where the 2mm rod contacted them as the rod was being forced into a staple shape. The bottom of the top die took a real beating, but the radii at the top of the U-bolt slot in the base die also took a hit. I can't get a decent close-up picture of those areas so you're just gonna have to trust me on that one. Other than upping the wall count and infill, I couldn't think of an easy way to beef up the top die. The bottom die on the other hand was easy. I used steel, in the form of a pair of 1/4"-20 bolts. I punched a pair of holes through the base die, so that the outside of the bolt's shank replaced the radius in the slot for the U-bolt.

This is the parts of the second die, and the results of the second press.


I have the beginning of a squared off U-bolt going on there. The top die still took a beating, but not nearly as bad as the first time. If I make the top die out of steel I should be just about there. It's a simple piece of 5mm flat stock with a 2mm slot cut part of the way across it - eazee-peasee.

The is the second die set up to press.


Don

[ddmckee54]

Well, my shipment of donor axles failed to arrive. Apparently the US Postal Service lost my order, they were the last to touch it on October 29th - after that the order apparently disappeared into La-La land. I got a refund on that order and placed another order, this time from a US shipper. That order is supposed to get here Friday.

I did re-make the top die for the U-bolt bending contraption, milled it out of a chunk of 1/4"x3/4" hot-rolled flat stock that I had laying around. There was some improvement, but not as much as I would have liked. However, squeezing the legs of the U-bolt while it's still in the top die closes things up nicely. I haven't threaded the legs of the U-bolt yet, I've just been trying to get as close to a 90 degree bend as I can. Now I'm thinking that the way I'm forming the legs of the U-bolt will just smear those little M2 threads out of existence. I think if I slip some brass tubing over the threaded sections before I bend the legs, that should keep the M2 threads for being destroyed. I'll need to modify the lower die to accommodate the tubing though.

My order of 6mm OD O-rings arrived yesterday. Those are for the equalizer beam pivot brackets, to allow things to flex a little. I don't think I've ever received a package that was as well protected as that one was. The O-rings, all 100 of the little suckers, were in a small zip-lock bag. This bag, and a thank you for your order note, were then put in a slightly larger zip-lock bag and wrapped in a double layer of bubble-wrap. All of the above was stuffed into a bubble-wrap lined shipping envelope, which the US Postal Service actually delivered to me this time.

Since I had to modify both the front and rear differential housings, to give me a fixed location for the equalizer beam and torque rod pivot brackets, I need to re-print the diff housings. Soooo... I might as well change the filament in the plastic-pooping-robot over to black. That way I "shouldn't" have to paint the suspension parts black. I might as well print out enough parts for both axles while I'm at it.

Don

[frizzen]

For the shackle benders, what about designing to use some needle-bearing rollers as the radius for your hard corners? Or even trying embedded needles in a Hotrolled version

[Blender]

Pretty hardcore to make your own ubolts. Getting pretty close now. I would think having the threads formed first might be easier. A M2 die may not fit once the legs are bent.

[ddmckee54]

The 1/4-20 bolts that go through the bottom die form the outside of the U-bolt legs. I just counter-sunk the end of the slot in the top die and that helps to form the inner radius of the U-bolt legs. I have to cut the threads first, there only a little over 5mm between the legs of the U-bolt. While I have no doubt that there are people out there who can make and harden their own custom M2 dies that would fit in that 5mm slot, I ain't among them.

I ordered some 2mm ID brass tubing to protect the M2 threads while bending the legs, I have no local source for something like that. What did we do before on-line ordering? Don't answer that, I'm old enough to remember what we did back in the the "Old" days.

I re-made the top-die for the U=bolt bending contraption, I milled it out of a piece of 1/4"x3/4" hot rolled flat stock I had laying around. In the process of milling the top die I've discovered how poorly I've got things organized in my shop, and how badly I've neglected my little lathes/mills, I've got a Unimat SL that I purchased in 1973 from my local Sears catalog store. (Hold up your hand if you actually remember what a catalog store was, or even a paper catalog for that matter.) I've been collecting tooling over the years, but not that much experience. About 5-10 years ago I had the chance to purchase a Sherline 4000 and a BUTT-LOAD of tooling from a gentleman who was down-sizing his shop, it's mostly been sitting in a box since then. That has all changed in the last couple of weeks, they are now getting the TLC and attention that they deserve.

Don

[Zabco]

Oh wow, cool. I have a Unimat SL also. Was the first power tool I ever bought. Bought mine a couple of years before you and got it through Montgomery Wards (remember them?). Was right around $200 if I remember correctly. Heck of a lot of money back then for a kid in high school. Also learned real quick that as a rule of thumb however much the machine costs, you need to spend at least that much more to get tooling you need to use it. I also have a Sherline mill and lathe both equipped for CNC. Only used it on lathe once but use on mill quite often. Today I primarily just use the Unimat as a drill press for tiny holes. Love that little machine, carried it with me all over the country.

I have made several u-bolt benders similar to what you are now doing and damaging the threads was never really a problem. Didn't have an arbor press to push the plunger into the die so used to use a bmfh. This often led to bent/broken plungers. The biggest issue I had was getting the legs of the u-bolt to end up the same length. Today I make up/use benders that hold one leg in position and then bend the bolt around a pivot of the size needed.

[ddmckee54]

Zabco:

Yeah, I remember Monkey Wards. Now that you mention it, it might have been a Wards catalog store. I know a couple years later when I bought my stick welder and my band saw, THEY came from Sears - also the store was in a different town. That little Unimat has survived 8-10 moves over the years. I don't like the round column on the Unimat, but I DO like having the quill for drilling.

I'm thinking it might not be a bad idea to cut and thread the legs of the U-bolts extra long. I can always even them up later.

[Zabco]

Growing up as a kid I always loved to go through the hardware department of Sears stores. Didn't really know anything about machine tools and the saws and drill presses and lathes in Sears always fascinated me. Then I bought my first table saw from Sears and learned why their prices were lower than everyone else. Couldn't keep that thing in alignment for anything. Got rid of it in a moving sale and started going to real machine tool dealers. Their basic hand tools were ok, I still have my first set of sockets and wrenches from them, but power tools, uh-uh. Now Lowes sells the Craftsman name tools and I won't even look at them.

Good idea with the u-bolts, I had never thought of that. Considered how to make the 'squared' u-bolts?

[ddmckee54]

A squared off U-bolt is what I'm aiming for. But.... that's gonna be on hold - at least for a little while.

Meanwhile I'm going to nominate myself for Bone-head of the Week-Month-Year. (Take your pick.)

Last night, while working on a more permanent base to mount the Sherline onto, I managed to drop the dang thing. Not the base, I managed to knock the Sherline off the bench. Although the base wound up on the floor too, when I made a grab for the lathe. It, the lathe, bounced off a cabinet and a shelf on the way down and tried to spear the concrete floor. That concrete has been hardening for over 125 years, it barely even got scratched.

The headstock end of the lathe took a hit though. I tore the lathe bed apart and there appears to be only one casualty. I mentioned that I had purchased the lathe and tooling from another gentleman several years ago when he sold the whole kit-n-kaboodle to me. He bought most of the extra doo-dads that Sherline sold for the lathe, among them was the manual threading attachment. This attachment lets you do single point threading on the Sherline. The dog that engages/disengages the lead screw from the change gears is what took the hit.

Since the only time that is needed is when you're threading, and it will be MANY-MANY moons before I'm ready to jump down that rabbit hole - I'm just going to take it off for now. I'll just add it to the other busted parts in the "Box of Shame".

I've looked on the Sherline parts web-site, and it looks like that particular part is no longer available. It's beginning to look like when the single point threading time does come, I'm going to have to make a repair part before it can ever happen.

Meanwhile, now that I've got the lathe bed torn completely off, I'll clean the gunk off the spots I couldn't get to previously. Then MAYBE I'll be able to get back to where I was 4-5 hours ago - before the boo-boo.

Don

[Blender]

Sherline lathe is my most used tool by far. My matching mill is CNC but I don't use it as much. CNC quickly became a hobby within a hobby. I just want the parts. Super exciting to see you've busted out the lathe. I had a harbor freight 7x10 or whatever and hated it. Sure it could take a heavier cut, but I could never get the tailstock aligned well, nor the bed and head just right. The sherline is a workhorse as long as the cuts are gentle.

I mounted the lathe to a big chunk of aluminum rectangular tube. I think it's around 2" x8" x whatever length with 0.25" wall thickness. Found it in the scrap section of tye local metal shop. Lets me tuck some wires in the hollow and mount a DRO. Rubber feet on the bottom. Love that machine.

[Zabco]

Oh man, reading that made my head hurt. I'm really glad the damage was not any worse than that. Find it hard though to think that Sherline can't provide a replacement part. I have the threading attachment also and while I don't use it a lot I do use it. Biggest issue with it is just figuring out which gears I need and the order to install them. If you do start to do threading, piece of advice. Always remember to back out the cutter before returning it to the start of the next pass. Especially if using a carbide cutter. I've broken off way too many cutter tips because I can't remember to do that.

[ddmckee54]

Blender - Almost 50 years ago my first job was in maintenance in a plant that made plastic laminates of various types and thicknesses. I got some of the reject pieces before I left. I'm using a piece about 1-1/8" thick for the base. It's straight, heavy, and resistant to oil. The base for the Unimat is similar, but its' core is canvas instead of kraft paper.

Zabco - While I was looking on the Sherline web-site for repair parts last night I did see a calculator/spreadsheet that will give you the gears to use. I couldn't get it to work, it gives me a lot of #REF errors, but that could be because I'm running Open Office on this PC and not Excel.

After doing a couple of last minute outdoor jobs, like making sure the snow blower actually runs before I REALLY need it, I decided to take another look at the carnage from last night.

I've still got the one casualty, but it's not a fatality like I originally feared. I was able to thread a screw into one of the parts that were jammed together, and then clamped the head of the screw into my vise. A piece of wood, a smallish BFH, and a little judicious tapping later and they were apart. There were several non-factory burrs and dings that needed to be dealt with. The only downer now is that the drive pin that keys the gear to the shaft driving the lead screw is MIA. But that looks to be a piece of 3/32" rod, so replacing it is no biggie.

I'm still not quite back to where I was last night, pre-fall, but everything is moving much better than before.

I know Sherline says to use light oil to lube things, but right now all I've got other than 5W-30 is 3-in-1 oil - what do you guys use?

Don

[ddmckee54]

Well, I got some parts today, my axle order arrived and I got the 2mm ID tubing I ordered.

Not my first order of axles, this was the second batch that I ordered. Surprisingly, or maybe it wasn't really THAT much of a surprise, all 6 of then feel very crunchy when I try to turn them. I had hoped that this lot might at least turn right out of the bag. I suspect that I'll find no clearance in the spider gears.

You remember how impressed I was with the care taken to protect the O-rings? Well, let's just say the shipping for the tubing is on the other end of the spectrum. They were shipped in a zip-lock bag inside a non-padded shipping envelope. And not even a heavy duty zip-lock bag like the O-rings had. The shipping bag looks it's gone several round in a fight that was above its' weight class. There's 6 or more holes through the shipping envelope, but only 1 of those is anywhere close to where the tubing ends were. But there's no holes in the zip-lock bag, so whatever chewed those holes in the shipping envelope was on the outside trying to chew its' way in. Not on the inside trying to chew its' way out to make a break for it. All the tubing has a slight kink to it, but I only need short pieces so I'll just avoid the bends.

Don

[Blender]

1.125" plastic slab sounds like a great lathe base.

That's a relief the lathe isn't as far gone as feared. I use 3N1 oil since I usually have it on hand as an "indoor" oil.

[Zabco]

Really glad to hear that the damage is not as bad as feared and that you will be able to get it fixed.

I have the tables that Sherline has for both imperial and metric threads for their lathes, it's just that I always have to look up the instructions as to where A gear goes and B gear goes, etc. BTW I would recommend that you ditch the Open Office program and replace it with Libre Office. Both are free and both started from the same source code. But Open Office is not being worked on and has not had an update in over 10 years. Libre office has an active group of workers constantly working on updates. I found that it works much better.

3 in 1 oil should work just fine. I use a gun oil just because I have it. Been using it for over 15 years with no problems.

I usually buy rod and tubing from either ksmetals.com or mcmaster.com depending on size and material. Probably not the cheapest sources but I have never had any kind of shipping issue with either one. My LHS does not keep up their stock of raw materials like they used to so I had to go to internet orders.