Frederic's Backbone Kart

[bigfootrules31]

my brain hurts from reading this thread

 

[jorge0136]

The actual trigger for all this re-engineering was my dropping the slip-in spider shaft on the floor and DENTING it. A half-inch diameter, 3" long shaft falling to the floor should not DENT upon impact. And not a little ding either. It mushroomed! I cleaned it up on the lathe and intended to put a simple washer on the end to make up the minor length difference, but that just seemed cheesy.

Ok, this makes sense now. I would think you should be able to use the thing as a drift punch, not mushrooming on the floor. I also understand picking up something that should never break on the cheap. A little extra weight, but this isn't a race car. Plus you get extra parts, sounds like a easy decision after all. Making up a housing out of a bunch of panels sounds like more engineering than I could manage to weld together.

I hope you keep documenting this well, I have zero experience with modifying geared drive lines and am always curious. For example the roller bearings, I have no idea what we are speaking about here.

You mentioned that cub cadets might have suitable transmissions. I know my dad has a couple ancient old tractors sitting in the back yard maybe I need to go look at them now.

800 lbs dry... wow you are building a machine here. Even where wild guesstimates are involved.

 

[frederic]

Bigfoot - may I offer you some aspirin? It's also good for the heart according to my doctor!

not mushrooming on the floor

Yes, I would have throught so. It didn't mushroom that much, just enough where I couldnt' slip the spider gear onto that end without tapping the gear on with piece of 2x4 as a hammer, or taking off the 4/1000ths of an inch of "mushroom head" as I did on the lathe.

A little extra weight, but this isn't a race car.

No, it's for a four year old who eventually will be an 18 year old. This is why I'm building it larger than seems reasonable. I'm hoping to build one, hand it over, and he gets 13-14 years out of it.

Making up a housing out of a bunch of panels sounds like more engineering than I could manage to weld together.

I've built several full-size differentials for race cars and pickups in the past, so aside from making adjustments for the semi-circle pot metal differential "bushings", I just rescaled my existing templates to be sized for the peerless differential and made minor adjustments to sizing.

Where I would have spent a lot of time is jigging... I have in the attic a jig for a full size differential housing that would contain the typical racer-loved Ford 9" bits, but I don't have any jigs for something this small. The Audi diff eliminates all that work and hassle. If I had more available time for this project I'd probably have done it and used a different differential, maybe one of the Bolens/Ariens/Club Cadet ones i saw on ebay.

For example the roller bearings, I have no idea what we are speaking about here.

Most kart-sized bearings are two rings with a set of hardened steel balls in between, so the inner ring can spin freely inside the outer ring but not move around left and right and be all wobbly.

Roller bearings are essentially the same thing, except that the steel balls are replaced with steel rollers. This makes the bearing stronger.

Tapered roller bearings are similar, except the rollers are not cylinders and instead cones. This still allows the inside diameter of the bearing to be a straight hole for an axle, but the outside of the bearing is also cone shaped. This in turn has to ride in an angled collar, either pressed in or machined in.

The angled rollers can be longer than straight rollers for a given bearing width and therefore are stronger. This is why they're all over automobiles and trucks. They're used in transmissions, differentials, axles, etc. Some german cars even use tapered roller bearings in their steering columns nowadays.

You mentioned that cub cadets might have suitable transmissions. I know my dad has a couple ancient old tractors sitting in the back yard maybe I need to go look at them now.

Differential, not transmission :-D. Larger tractors, i.e. bigger than your average riding mower, have differentials shaped much like an automotive differential and is something I instinctively know what to do with. I'm new to mower parts and karts actually.

800 lbs dry... wow you are building a machine here. Even where wild guesstimates are involved.

Well, if one were to be "technical" one me I'm probably not really building a go-kart, but an off-road buggy.

For adults our size, it's a two seater. For children my son's age, it could be a four seater. That should give you an idea of how big it is.

I'm measuring it in trips, i.e. how many times I trip over it while working on other things. It takes up a lot of room and I've skinned my knees and ankles on it several times because it's smack right in the middle of what little open space I have in that garage bay.

See, I used to have both garage bays however a few years back the attic became infested with carpenter ants and the "antman" who came to spray made us remove everything that was in the attic. It ended up in my "project bay" temporarily, however we all know how "temporary" works out in the end.... ;-)

 

[jorge0136]

may I offer you some aspirin? It's also good for the heart according to my doctor

Asprin is a intresting drug, pain killer and a blood thinner. Amazing how nature works. Don't forget a dose too, your blood will tend to clot very easily after coming off of daily aspirin aka high risk for heart attack.

Enough of my babbling.

Yes, I would have throught so. It didn't mushroom that much, just enough where I couldnt' slip the spider gear onto that end without tapping the gear on with piece of 2x4 as a hammer, or taking off the 4/1000ths of an inch of "mushroom head" as I did on the lathe.

Still a flimsy part to be inside a differental. I need to get myself a lathe, sounds like an exceedingly useful tool. I have dang near everything else in my shop to fabricate things with, minus the lathe and the mill.

No, it's for a four year old who eventually will be an 18 year old. This is why I'm building it larger than seems reasonable. I'm hoping to build one, hand it over, and he gets 13-14 years out of it.

I'm hoping the kart I am building will be something similar in how I can modify the speed over time. Clever plan. Hopefully he will want to help you keep working on it at somepoint down the line.

I've built several full-size differentials for race cars and pickups in the past, so aside from making adjustments for the semi-circle pot metal differential "bushings", I just rescaled my existing templates to be sized for the peerless differential and made minor adjustments to sizing.

Where I would have spent a lot of time is jigging... I have in the attic a jig for a full size differential housing that would contain the typical racer-loved Ford 9" bits, but I don't have any jigs for something this small. The Audi diff eliminates all that work and hassle. If I had more available time for this project I'd probably have done it and used a different differential, maybe one of the Bolens/Ariens/Club Cadet ones i saw on ebay.

Audi diff sounds as though it was a steal of a deal after all then. Even after jigging up the whole housing it would have been some adventure welding it together. I am intrested in seeing how this is done? Have you already documented it on one of the ford 9" diffs?

Most kart-sized bearings are two rings with a set of hardened steel balls in between, so the inner ring can spin freely inside the outer ring but not move around left and right and be all wobbly.

Roller bearings are essentially the same thing, except that the steel balls are replaced with steel rollers. This makes the bearing stronger.

Tapered roller bearings are similar, except the rollers are not cylinders and instead cones. This still allows the inside diameter of the bearing to be a straight hole for an axle, but the outside of the bearing is also cone shaped. This in turn has to ride in an angled collar, either pressed in or machined in.

The angled rollers can be longer than straight rollers for a given bearing width and therefore are stronger. This is why they're all over automobiles and trucks. They're used in transmissions, differentials, axles, etc. Some german cars even use tapered roller bearings in their steering columns nowadays.

Ahh I know what you are talking about now, thanks for clearing it up. Are tapered roller bearings merely harder to machine and that is why they are less prevalent? How do the tapered bearings do with side loads? Seems as though they might fail if the force was on the skinner end of the cone. Is this just my emperical mind running wild?

Well, if one were to be "technical" one me I'm probably not really building a go-kart, but an off-road buggy.

For adults our size, it's a two seater. For children my son's age, it could be a four seater. That should give you an idea of how big it is.

I'm measuring it in trips, i.e. how many times I trip over it while working on other things. It takes up a lot of room and I've skinned my knees and ankles on it several times because it's smack right in the middle of what little open space I have in that garage bay.

See, I used to have both garage bays however a few years back the attic became infested with carpenter ants and the "antman" who came to spray made us remove everything that was in the attic. It ended up in my "project bay" temporarily, however we all know how "temporary" works out in the end.... ;-)

Sounds like your son is going to need to bring some friends along for the ride.

I understand about things moving "termporarly" and never going back to where they belong. I also understand about a tripometer. Nothing makes something meaningful like physcial pain.

So are you going to be able to pull off the pulley on a shaft plan?

 

[frederic]

Don't forget a dose too, your blood will tend to clot very easily after coming off of daily aspirin aka high risk for heart attack.

Quitting smoking would probably lower my risks also.

Enough of my babbling.

Feel free, I do it all the time in case you haven't noticed.

I need to get myself a lathe, sounds like an exceedingly useful tool. I have dang near everything else in my shop to fabricate things with, minus the lathe and the mill.

Between a lathe and a mill, you can make almost anything, and if you can't directly you can make tooling for either machine so you can make almost everything.

Clever plan. Hopefully he will want to help you keep working on it at somepoint down the line.

Assuming his current behavior and interests at age four continue, his interest in tools will exceed mine. My biggest concern at the moment is safety, and I've been drilling it into his head since day one. At this point he won't even set foot in my shop/garage until he puts on his heavy denim apron and his toddler sized "eyemuffs" as he calls them (safety goggles).

I even let him use the bigger machinery, as long as I set them up ahead of time for a task and jig things so limits cannot be passed. A year ago (or so) a friend offered me a few bucks to skim his V6 racing heads so I made a jig, clamped them to my milling machine, and let me son turn the x and y cranks to do the actual skimming. Since the cut was completely across the head surface in all directions, it didn't really matter who moved the x-y table around. My son certainly moved it about 1/5th the speed I would have, so the finish is even better.

The friend/customer was really unhappy upon seeing the youtube video, which I have since taken down. He "paid for professional service" and didn't want my then 3 y/o machining his heads. I told him for $100 he gets what he pays for lol. Seemingly he didn't appreciate my sarcasm either.

seeing how this is done? Have you already documented it on one of the ford 9" diffs?

I might have pictures on my old Dell laptop. The next time I see it I'll fire it up and see if they are there. If not, I'm happy to draw up a quick not-to-scale of the various pieces to illustrate how it's templated out. The templates are easy, you're essentially make a low-resolution sphere. Each "panel" in the sphere is flat and together, it's a multi-sided shape that from a distance looks sphere-like. Here is an example I leeched from the web, and my handiwork looks very similar. The carrier is inside and the pinion gear and u-joint would be facing away from you which is why it doesn't show in the picture. You can see the flat pieces that are welded together to form the "sphere" and how it's somewhat oblong rather than roundish.

I know what you are talking about now, thanks for clearing it up. Are tapered roller bearings merely harder to machine and that is why they are less prevalent? How do the tapered bearings do with side loads? Seems as though they might fail if the force was on the skinner end of the cone. Is this just my emperical mind running wild?

Roller bearings are stronger than ball bearings in the rotational plane, meaning that if you have a roller bearing in a housing and slip an axle through the bearing, you can put weight on the housing and it's very strong. It's stronger than a ball bearing because the roller has more contact patch with the inner and outer races than a ball bearing, however it shares one defect with the roller ball bearing and that it does not like lateral loads - i.e. side to side loads. For an axle that's located in place by another means this is not an issue but in some configurations there's a tendency for the load to push, or pull the inner race out from under the outer race.

This is a load that occurs all the time on a full-size vehicle. Every time you corner, hit a bump, drive off-road, there are lateral loads on the wheel bearings. So, to give the bearing strength in a lateral plane, you simply tilt the rollers to an angle. Let's be extreme and tilt them to 45 degrees. That means the bearing is equally strong laterally as it is radially. Why? Because the angle of the rollers is the same whether you look at the bearing radially or laterally (through the axle hole).

Now about the taper. A bunch of rollers inside two rings where all the surfaces are parallel to each other (outer race to rollers, rollers to inner race) this is easy. No taper necessary. But if you change the angle of the rollers inside the bearing, then you have to taper them, because the further away edge of the roller will want to rotate faster than the inside edge, because it's covering a larger distance.

Tapering the rollers solves this nearly perfectly. It's the same reason why ackerman angles are put into steering systems - the outer wheel (outer edge of the roller) travels a greater distance than the inside wheel (inner edge of the roller).

Sounds like your son is going to need to bring some friends along for the ride.

He already has the girl-next-door (almost age four) in mind ;-)

So are you going to be able to pull off the pulley on a shaft plan?

Making it fit together I can do, no problem. What I have to figure out is how much to gear down the motor and if a clutch is necessary to allow the motor a little start-up time before it's engaged to the differential/axles/rear wheels.

Why? Because the differential is a 4.11:1 ratio, and I'm not sure any reasonably-sized electric motor is going to like that when driving 18" diameter tires. Plus at full RPM (3600?) that would be way beyond a reasonable speed for my son. So to avoid insane start-up currents and hammering the bearings in the motor (assuming it can turn this load at these gear ratios) I'm thinking gearing it down a bit might be necessary. That also allowed me to fold the assembly over itself, meaning I can mount the motor above or below the differential and not have it stick forward snout-to-snouth like I was originally thinking. This is particularly where the extra pieces may come in handy - pulley hubs, jackshaft pieces, and so on.

Making the bits I have work is very easy. Arriving at a sound design that doesn't cause electric motors to burst into flames is the real work ;-)

Of course I could install a bigger motor, but then that opens up more cans of worms. See, I'm trying real hard not to go overboard. I have this 11" diameter transwarp motor in the attic calling me while I sleep. I'm not listening! I'm not listening!

 

[jorge0136]

Between a lathe and a mill, you can make almost anything, and if you can't directly you can make tooling for either machine so you can make almost everything.

That is what I am coming to realize, I think a foundry would also be tremendously useful. I have most of the parts for mine. I put together a forge over the summer and even that has to be a very productive tool. Very nostalgic as well.

Assuming his current behavior and interests at age four continue, his interest in tools will exceed mine. My biggest concern at the moment is safety, and I've been drilling it into his head since day one. At this point he won't even set foot in my shop/garage until he puts on his heavy denim apron and his toddler sized "eyemuffs" as he calls them (safety goggles).

I hope he keeps up the zeal for tools. That is somewhat of how I learned to wrench with things, holding bits and pieces for my pops. If he stays interested it should make for some fun projects for the two of you later. My nephew who is nearly 3 does the same thing with the safety glasses. He knows where they are and grabs a pair for himself every time he's in the garage with me. An apron might be a good plan for him he gets filthy out there.
I might understand being slightly upset seeing a 3 year machining the head of my engine. If it was explained as you did however all would be well. Speaking of machining where did you learn the practice? My dad learned to machine in the navy and if we get some equipment he is going to teach me the ins and outs of it. I don't know if we will be ready to be machining engines any time soon though.

The carrier is inside and the pinion gear and u-joint would be facing away from you which is why it doesn't show in the picture. You can see the flat pieces that are welded together to form the "sphere" and how it's somewhat oblong rather than roundish.

What are the advantages to your own housing? Lighter I imagine, is it stronger as well? Awfully spiffy looking when you are done too. I could see how that could be done with some work.

The tapered bearings I was having a hard time understanding till I looked at some pictures. It all makes sense now. Thanks for explaining.

Of course I could install a bigger motor, but then that opens up more cans of worms. See, I'm trying real hard not to go overboard. I have this 11" diameter transwarp motor in the attic calling me while I sleep. I'm not listening! I'm not listening!

Sounds like something your kid might need to install at a later date. Let him start getting the calls from the attic. Did you decide on what you want to gear it down too yet? This motor is beastly as it is and geared so high might send your kid to the moon! Are you going to do braking in the same fashion as last time, shorting out the motor? I saw you were asking questions about torque converters. Were you thinking about trying to use one of those to not burst the motor into flames? CVT clutch from a snowmoblie perhaps?

In a slightly unrelated topic, here a little while ago I was attempting to remove the intake manifold bolts of out my International 196 engine that I am rebuilding. Well the 40 year old bolt head decided to round off on me and I ended up using something similar to your "old guy" trick. The clearance around the bolt was such that I couldn't just weld a nut or another bolt to the end of it. It was hard to even get a socket in there to begin with. I had to use a tiny u joint to get the socket in there that rounded it off. Anyhow I ended up welding a rod to the top of the bolt and breaking the bolt loose. Welding it again loosen it. Repeat till hand tight. Stinker came out eventually.

 

[frederic]

That is what I am coming to realize, I think a foundry would also be tremendously useful. I have most of the parts for mine.

A foundary is a very useful tool, especially for materials like aluminum which have a much lower melting point. A good friend of mine (who lives 3 hours away) made his own foundry and it's quite large - I can put four V8 cylinder heads or two 4-bbl intakes in it at a time and pour bars or blocks from the results. If he and I could get together more often than once or twice a year, I'd save every piece of aluminum I could find and return home with really useful block-shapes to make stuff out of.

An apron might be a good plan for him he gets filthy out there.

I got my son the apron not to much to avoid dirt but rather to avoid "chips" from the mill and lathe from sticking to his very tender skin. Remember that chips are often really hot and have sharp edges, and toddler skin isn't like adult skin, it's very thin and tender.

Speaking of machining where did you learn the practice? My dad learned to machine in the navy and if we get some equipment he is going to teach me the ins and outs of it. I don't know if we will be ready to be machining engines any time soon though.

A lot of my friends are a little older, and had machines like this when I was much younger, so early on I'd simply use their machines to make my stuff, with their advice, guidance, and coaching.

Over the years we've spread out so much that the commute to borrow these machines was getting crazy, so after sending stuff to local machine shops I decided it would be cheaper and more fun to own the machines myself.

I'm still learning actually.

What are the advantages to your own housing? Lighter I imagine, is it stronger as well? Awfully spiffy looking when you are done too. I could see how that could be done with some work.

A welded housing is typically lighter than the cast iron lump and much stronger because the housing itself is longer, moving the joint between the axle tubes and the differential housing further away from the differential. Steel can be dented whereas cast iron doesn't dent on impact and instead fractures.

The tapered bearings I was having a hard time understanding till I looked at some pictures. It all makes sense now. Thanks for explaining.

You're welcome.

Did you decide on what you want to gear it down too yet?

No I haven't, and I've shelved that for "occasional thinking" because I have some time before I have to make that decision. I'm still working on the suspension, spindles and hubs and once that's done I'll be forced to either make a decision or do a few experiments then based on that make a decision.

I'm very much open to ideas. Whatever I do, I want the moving bits to above or at least the rear of the chassis and not forward along the backbone, so little fingers and elbows won't get into them.

Are you going to do braking in the same fashion as last time, shorting out the motor?

I'll be doing something a bit different, depending if my test controller works the way I anticipate or not. But yes, the motor will be the drive and the braking mechanism.

I saw you were asking questions about torque converters. Were you thinking about trying to use one of those to not burst the motor into flames? CVT clutch from a snowmoblie perhaps?

Even though the Audi diff and extra parts solved a lot of problems I was expecting, the gearing is not exactly ideal, so I will either need a clutch or torque converter to allow some controlled slip between the motor and the differential's pinion shaft, or maybe some gearing through chains or belts first. I put that off and I think about it every so often but I haven't put anything down on paper yet. I don't have to "right now" because I'm still working on the suspension bits, hubs and spindles.

it. Repeat till hand tight. Stinker came out eventually.

Glad it worked out for you. BTW, a friend of mine handed me a bunch of drilled and sleeved bolts the other day specifically made for this purpose. They are 3/8" bolts with a 1/8" hole down the center and a non-conductive insert is pressed into that hole - allowing the bolt to be placed in the hole against the broken bolt that's there, then the mig wire zooms down the non-conductive insert until it reaches the bottom. Once it makes contact with the grounded bolt inside, a weld puddle starts and that joins the broken bolt fragment to the bottom of the sleeved bolt. They're about 4" long so I imagine they're not designed for surface breaks where the broken part is exposed, but rather bolts that snap "way down" in the threads. The bolts have a hex top but the shank is unthreaded, feels like mild 1018 or 1020 steel.

I have my spindle/hub designs down and the local metal supplier is hacking up the pieces, and they should be ready in an hour and then I'll have some more to post finally ;-)

 

[freakboy]

very thin and tender.

you made me hungry

 

[frederic]

Now I know why you call yourself freakboy. Uncontrollable cannibalism.

Anyway, just picked up the remaining materials to make the hubs and spindles (front and rear) so it's time to sneak out in the garage and make some progress.

 

[freakboy]

Can you get video of you machining the parts?

 

[jorge0136]

I second the request for the video if you could.

A foundary is a very useful tool, especially for materials like aluminum which have a much lower melting point. A good friend of mine (who lives 3 hours away) made his own foundry and it's quite large - I can put four V8 cylinder heads or two 4-bbl intakes in it at a time and pour bars or blocks from the results. If he and I could get together more often than once or twice a year, I'd save every piece of aluminum I could find and return home with really useful block-shapes to make stuff out of.

I hadn't even thought of melting things down into billet to machine. I don't think I am going to make my foundry nearly as large as the one you are talking about there. It will be a waste oil furnace and should be hot enough to melt cast iron.

A lot of my friends are a little older, and had machines like this when I was much younger, so early on I'd simply use their machines to make my stuff, with their advice, guidance, and coaching.

Over the years we've spread out so much that the commute to borrow these machines was getting crazy, so after sending stuff to local machine shops I decided it would be cheaper and more fun to own the machines myself.

I am thinking along the same lines in paying big bucks to machine shops. I feel as though I am sending some machinists kid to college on my dime. Maybe once I have my own machine they can help me learn the trade a tiny bit.

I don't have to "right now" because I'm still working on the suspension bits, hubs and spindles.

Please tell us a bit about the design of the hubs and spindles if you could. Are the wood spindles on the front permanent?

They're about 4" long so I imagine they're not designed for surface breaks where the broken part is exposed, but rather bolts that snap "way down" in the threads. The bolts have a hex top but the shank is unthreaded, feels like mild 1018 or 1020 steel.

This tool could have come in handy a couple times. I've the head off of bolts snap off a couple different times now. Once inside the head of my engine. I ended up drilling it out tapping a left hand thread into it and bottoming out a bolt into the threads. Not a very good solution.

Looks like a healthy chunk of raw materials there. How big a dent did that put in your wallet?

 

[frederic]

I second the request for the video if you could.

I will see what I can do.

I hadn't even thought of melting things down into billet to machine. I don't think I am going to make my foundry nearly as large as the one you are talking about there. It will be a waste oil furnace and should be hot enough to melt cast iron.

The crucible in my friend's foundry is about the size of a 10-gallon bucket, give or take. Aluminum melts somewhat quickly but iron and steel take forever. Aluminum is much more expensive than steel so saving all your milling and lathe chips to be tossed back through the foundry makes a lot of sense.

I am thinking along the same lines in paying big bucks to machine shops. I feel as though I am sending some machinists kid to college on my dime. Maybe once I have my own machine they can help me learn the trade a tiny bit.

Machine shops still have their purposes. One reasonably close to me accepts G-code by email and they'll cut and paste that into their CNC equipment, then charge based on final weight of the material plus $75 an hour. They have a 5-axis milling machine so to me that's worth spending dollars on if I really do need accuracy better than a thou. Most of what I make barely requires a hundreth of an inch of accuracy. The parts for my son's kart can be "way off" in this regard, until I reach the point of machining high speed rotating parts (pulleys, shafts, gears) and of course the housings for those parts.

For example, the a-arms were measured out with a tape measure, clamped, and welded together. The two uppers should be identical and the two lowers should be identical, yet they're all off a little here and there. It matters naught because of the rod ends and the fact that I hand-fitted them to balance out the minor differences side to side. For a one-off this is good enough for mass production, I wouldn't even consider it.

Please tell us a bit about the design of the hubs and spindles if you could. Are the wood spindles on the front permanent?

The front "wooden" spindles which I affectionally have referred to as "beehives" (my son came up with that) were just mock-ups when I was thinking a large chunk of aluminum would make a great spindle. It would actually, however I decided to use them in the rear instead and weld together various machined parts to make the front spindles.

I made this change because I'm no longer using the lawnmower wheels and tires, all of which have a 3/4" diameter center hole with more offset than I'd prefer. I was going to change the backspacing by hacking off a section on the inside of the wheel and welding it to the outside, however I couldn't get any of the tires off so I could chuck the rim in my lathe to do a reasonably precise cut. Then, I found brand new 18x9.50-8 tires on ebay with brand new 4-hole wheels for $20 a pop, with off-road lugs, a valve stem, I decided lets start fresh. So because I need a 4-hole hub now instead of a 3/4" diameter shaft sticking out, this required me to change the design quite a bit actually.

Looks like a healthy chunk of raw materials there. How big a dent did that put in your wallet?

The materials today would have cost me $88.71 according to the invoice. I paid for it with "store credit" as last fall they offered me a deal whereas they'll pay me $40 an hour plus provide whatever cutters are necessary for me to machine these weirdo little parts for a customer of theirs. And they were weird. Anyway, I accumulated for myself an approximate $400 credit which as of today I've used most of it.

Anyway, it's getting late, let me see if the camera is charged to take video and I'll get started before the mosquitos in the garage wake up and gnaw at me.

 

[frederic]

I attempted to capture some video this evening however the problem I have is there's no room for a tripod. I either bump into it constantly, or it's in a position where all you see is the back of my bald head.

Som I'll need a little time to figure this out a bit. I thought I had a tabletop tripod, I'll have to look for it.

 

[freakboy]

Ask your son to hold the camera. or sit the camera some where were we can see the work.

 

[frederic]

I'll try resting it on the drill press table next to the lathe. If I give my son the camera we'll just have video of his toes, thumb, and the ceiling.

 

[freakboy]

LOL i know a few 16 year olds that your sons video taping skills surpass. lets just say i was making a vid and didnt wana put a shirt on next thing i know hes all the way zoomed in on my nipple. I also learned wire wheel and no shirt = pain.

 

[frederic]

Here is the video you both requested. Hope it's to your liking. A professional videographer I am not

http://www.youtube.com/watch?v=daTbGx6Feqw

 

[freakboy]

Nice work!

 

[jorge0136]

Excellent video.When you begin actually boring out the hole how are you determining how far the bit has traveled? Is it all the numeric indicators on the hand wheel? At one point the piece starts to automatically move on it's own, how is it that you control that automatic movement? That is a healthy "bee hive" of aluminum for that bearing to rest in. Is it so much larger than normal because of the soft material? You mentioned a boring bar would you mind explaining a little bit of how that works? If You get tired of my endless questions I understand.

Machine shops still have their purposes. One reasonably close to me accepts G-code by email and they'll cut and paste that into their CNC equipment, then charge based on final weight of the material plus $75 an hour. They have a 5-axis milling machine so to me that's worth spending dollars on if I really do need accuracy better than a thou.

I had to look up how you get 5 axis out of a milling machine. Makes me want to make something overly complicated just to see it work. $75/hour seems well like a lot of money.

The crucible in my friend's foundry is about the size of a 10-gallon bucket, give or take. Aluminum melts somewhat quickly but iron and steel take forever. Aluminum is much more expensive than steel so saving all your milling and lathe chips to be tossed back through the foundry makes a lot of sense.

I would have wasted a huge chunk of metal I think had you not mentioned this. What did he use for a crucible? I'm going to have start looking for some old metal. Sounds like you have quite the deal worked out with the metal shop. How did you swing that?

 

[frederic]

Nice work!

Excellent video.

Thanks!

When you begin actually boring out the hole how are you determining how far the bit has traveled?

The handwheels on my crossslide are marked in thousanths, so each line on the dial is one hundreth of an inch of cutter travel. One full rotation is 0.100" Ten full rotations is an inch.

Since the diameter of the hole was to be 2.430", the radius is 1.215, minus 5 thou, that's 1.21" of travel per cut to increase the depth. I "eyeballed" this on the handwheel because I used a dial indicator to get the last cut which increased the diameter to precisely 2.430". This is how one can get "thousanths" on a machined marked up in "hundredths".

I always use the dial indictator for final cuts because my lathe is very old (1959) and there is some wear and even though it's fairly accurate this accuracy changes across the length of the bed "just a hair". As much as three or four thousandths of an inch. While that doesn't seem like a lot that's enough to mis-cut parts like this so the bearing cup (the tapered ring) could fall out. That's why I measure, and measure, and measure, just to be sure.

So my work is as accurate as my dial indicator, which according to the box is accurate to 1/10000th of an inch, even though it only displays 1/1000th of an inch. How that works I have no idea but it's the reason why I didn't buy a $14.95 chinese made dial indicator, and instead asked for a $250 one for christmas a couple of years ago. I have the cheapie import ones also, and I use them all the time for other things or when I need more than one indicator set up at the same time. But I use the fancy, highly accurate one for work like this.

At one point the piece starts to automatically move on it's own, how is it that you control that automatic movement?

This particular lathe has several transmissions. The primary transmission has three primary gears and 18 secondary gears, giving me 54 combinations. These control the rotation speed of the long acme screw that goes the length of the lathe bed.

That acme screw drives gearing in the cross slide, and depending how cross slide transmission is set, the acme screw will either move the crossslide towards/away from the headstock (left to right from the operator), or move the crossslide across the bed, parallel to the headstock (towards/away from the operator).

Another transmission on the headstock also is a "high/low" transmission, which changes the ratio between how fast the chuck turns in relationship to everything else. For making smooth machined surfaces this transmission is set for "high". For cutting threads, where you want the chuck to turn slowly and the crossslide to move quickly, it's set for "low".

In "high" mode there's another 3-speed transmision that changes the rotational speed of the acme screw which also impacts cutting speed versus smoothness, and is not engaged by design when cutting threads in "low" mode.

Between all these gears/transmissions I can turn material to silky smooth or cut threads as large as 1 TPI and as small as 100 TPI.

Is it so much larger than normal because of the soft material?

The spindle (the chunk of aluminum) is 6" tall x 3.50" wide by 3.50" deep, and the bearings will stick out about 1/8" bringing the total depth to 3.75". This 3.75" will be supporting an axle that's 4" long. This axle will have a wheel flange on the outside for me to bolt the wheel and tire to (4-110mm bolt circle) and on the inside will be a removable flange with a u-joint that will be driven by the half-shafts, and in turn driven by the audi differential.

3.75" is not a lot of width between bearings to support a wheel, 18" tire, and about 1/4 of a potentially 1000lb car. They're 6" tall because that's the most I could fit inside the wheels, and I have additional machining to do so the upper and lower rear "H-Arms" can be shoved in. I haven't made those yet nor have I made the cuts for them, and once I do it will make more sense as to why the rear spindles seem big.

You mentioned a boring bar would you mind explaining a little bit of how that works? If You get tired of my endless questions I understand.

Ask away, it's entirely cool. A boring bar is a long rod with a lathe cutter, much like the one in the tool post in the video, sticking out at the very end of the bar at an angle.

This allows a machinist to make strange diameter holes. If you want a 1/2" hole you'd use a 1/2" drill bit. But what if you wanted to bore a 0.518" diameter hole? Have you ever seen a 0.518" drill bit? ;-)

What one does is you drill the 1/2" hole (0.500") hole first, then put the boring bar and cutter into the toolpost on the crossslide, then center it precisely. Once that's done, you move the crossslide towards you or away from you depending on which side the cutter's on, a precise 0.009" and you then bore into the existing 1/2" hole. 0.009" times two is the 0.018" additional diameter increase giving you the 0.518" diameter hole you need in this example.

All a boring bar does is move the cutter off the toolpost and angle to cut an inside diameter. They're usually made of tool steel for rigidity especially when they are longer.

Does that explaination help?

I had to look up how you get 5 axis out of a milling machine. Makes me want to make something overly complicated just to see it work.

5-axis is common these days, but CNC machines can have more axis. I think 10 or 12 is the limit.

$75/hour seems well like a lot of money.

It is, however around here in the NY/NJ area that's about the going rate for custom work. Paying for 3-4 hours of labor is cheaper than buying a $3500 machine, especially if the job is a one-off or such a low production part that the purchase of the machine isn't justified.

I would have wasted a huge chunk of metal I think had you not mentioned this. What did he use for a crucible? I'm going to have start looking for some old metal. Sounds like you have quite the deal worked out with the metal shop. How did you swing that?

Since my friend's foundry is "only" for aluminum, he uses an iron crucible which to be honest I'm not sure where it came from. It's about a foot and a half in diameter at the top, about two feet deep, and rounded like a ball on the bottom. Basically his furnace cooks the aluminum the same way you'd cook a stew on a stove, then the whole furnace is on a stand that allows the furnace to rotate, and that's how pours are done.

The whole thing, stand and all, is about 4' high. It runs on acetelyne and oxygen just like a welding/cutting torch.