Ultralight Rev-Tri-Go-Kart build

[itsid]

'Sid, the first one has the cross section I'd recommend, but that actual part is designed to turn a standard rail into a structural component in a sliding system. It's used to make custom machines, with that part being a three sided sliding bearing. It's not designed or intended to be a fixed component.

The second one was a link to big for my internet connection; can't open it tonight....

Pat, I know.. but it's just a ptfe pad, cut small grooves for the T-nuts and attach them with longer bolts, the ptfe pad will only act as a vibration damper once all bolts have been tightened down.
I'm also quite positive that you will not be able to crack the ptfe and end up with a sturdy system to mount 'whatever you want' in a non sliding manner

the second link is just a catalogue of such sliding bearings in different sizes and with different flanges, nothing special.

Yes, something like that, hugging on 3 sides, but without plastic inserts would be right. But this particular part costs $60 each in 15 series. And it'll be flexing because of plastic inserts.

That plastic is (well should be) ptfe.. the densest I know, that stuff isn't flexible at all;
It'll absorb some vibrations at best, but isn't going to flex enough to notice.

'sid

 

[machinist@large]

Well, I was suspecting it'll be the weak point. But I have to constantly remind myself to not over-engineer. Chinese kids cars at wallmart use all plastic, and hold up just fine (although at slower speeds).

What if bolt it all the way through in two places with 1.5x1.5 backing plates on the other side?

Engaging more than one face of t-slot means I can't use a flat plate anymore. That complicates things a lot

The kingpin whole(s) is 3/8 or 7/16, that leaves plenty of wall, over 1/4" in each case. Multiplied by 2" of height - i don't think it's going anywhere. But it's possible to go with 1.25 thick plate, I guess.

I was considering two holes vs straight through kingpin and decided two will be stronger - as they leave a solid crossection in the middle of the part. And this is all static connection - the rotation will occur at the balls in the rod ends. But I can be wrong. Straight through is surely easier to do.

For the axle hole - yeah, 1.25 aluminum will be probably better.
And it'll make the business of adding control arm easier. I'll just drill two small holes on 1.25 side and attach the arm.

I want arm to be separate and replaceable part. First of all - it WILL bend during accidents. And second it'll make steering setup/adjustments easy.



I don't insist on anything. I just need to make this part. The way I simplified the part - it can be made from flat piece, with simple tools you have! I just need to buy rims first to finalize the dimensions. Right now i only have tires.

Do you think it's necessary to drill the axle hole through? I was hoping it can be just taped hole, so I don't need no nuts, just one bolt and lots of locktite. The wheel will have bearings, so this is non-moving part will only need to withstand vibrations.

Yes, something like that, hugging on 3 sides, but without plastic inserts would be right. But this particular part costs $60 each in 15 series. And it'll be flexing because of plastic inserts.

Vlad, I know I can answer most of your questions, and finding out you're in the 1/2 hour away range means we can brainstorm this in depth in person......

The reason(s) I have to hoist the flag of tonight is the fact that my first alarm clock goes off somewhere between 3 & 4 AM. Depending on what the weather hands me, I still have to be on the clock by 6. The fact that I'm ranked as one of the worlds worst typist's doesn't help...

You've got some great ideas, it just comes down to how we figure out to build it. You stated in your PM that you're still in the planning stages; also, seeing as we're in the same slice of frozen tells me we have time to try to sort this out before the young one get restless.....

 

[vlad]

How to put this-...." looking for love in all the wrong places...."

I think you are much too quick to focus on one solution and then spend too much time "over-engineering" to fit a flawed concept instead of revisiting the original concept and looking for solutions to eliminate the need to overcomplicate and "over-engineer" the solution. The best solutions are usually the easiest. ... You seem to be very hung up on this extruded aluminum piece and ignoring the great lengths you are going to to use it.

Also- Why do you need all this adjustment in camber in a non-suspension kart. A few minutes studying the "Akerman" thread and you would have the knowledge to build a steering system simply and correctly the first time. ...

Just saying. .....

Because I watch too much F1... I don't know what camber will work the best with race tires on ultralight go-kart, hence I want to be able to adjust it.

And just how from this hub design did you came to the conclusion that I'm NOT going to do the correct ackerman geometry??? I don't really need to study ackerman thread to learn about it. Already spent way too much time studying things in university.

 

[vlad]

That plastic is (well should be) ptfe.. the densest I know, that stuff isn't flexible at all;
It'll absorb some vibrations at best, but isn't going to flex enough to notice.

'sid

Well, that still leaves the part where it cost $60 a piece

 

[machinist@large]

Pat, I know.. but it's just a ptfe pad, cut small grooves for the T-nuts and attach them with longer bolts, the ptfe pad will only act as a vibration damper once all bolts have been tightened down.
I'm also quite positive that you will not be able to crack the ptfe and end up with a sturdy system to mount 'whatever you want' in a non sliding manner

the second link is just a catalogue of such sliding bearings in different sizes and with different flanges, nothing special.


That plastic is (well should be) ptfe.. the densest I know, that stuff isn't flexible at all;
It'll absorb some vibrations at best, but isn't going to flex enough to notice.

'sid

'Sid, you're on the right track with your ideas, but I have to point out some things....

The plastic is UHMW, not PFTE; Ultra High Molecular Weight I can remember and spell; the full name for Teflon is outside that...

UHMW has descent structural properties, which is why it's used in this case; Teflon does not. Teflon is so soft that all engineering applications are captured only; I've damaged (and scrapped) a 1/2" X 3" bar by squeezing it to hard just trying to get it out of the box it got shipped in....

 

[vlad]

Attachment plate and back plate for two 5/16 bolts, drilled through 80/20 beam. 5"W 4.2"H. about 1/2 lbs each side

 

[itsid]

UHMW has descent structural properties, which is why it's used in this case; Teflon does not. Teflon is so soft that all engineering applications are captured only; I've damaged (and scrapped) a 1/2" X 3" bar by squeezing it to hard just trying to get it out of the box it got shipped in....

Hm *scratching the ol' head*

I have some ptfe heat insulators (16mm round),
It cuts nicely, but I can't damage it with blunt force;
LD or even HDPE can be deformed rather easily
and even PEEK gives away much sooner than PTFE.

Since UHMW is nothing but HDPE with a higher molecular weight
[0,93–0,94 g/cm³ for UHMW compared to 0,94-0,97 g/cm³ for HDPE]
I think UHMW PE (shore D 61) still cracks way sooner than PTFE [2,1–2,3 g/cm³]
and it's quite sturdy stuff (shore D 72)
which is ported to the brinell scale in the range of copper

But to be fair, never had a piece of UHMW to play around with (or at least not that I know)

'sid

 

[vlad]

Which of 7/16" rod ends on McMaster.com will fit best for this application? They all rated for loads 100 times more than I need

1. Inch sizes have a zinc-plated steel housing and chrome-plated steel ball (unless noted).

2. Inch sizes with grease fitting are easy to lubricate. Housing is steel. Ball is chrome-plated steel.

3. Inch sizes with self-lubricating insert have a zinc-plated steel ball that glides on a PTFE-lubricated, carbon-fiber-reinforced plastic insert, which provides wear resistance and doesn’t require lubrication. Housing is zinc-plated steel.

4. Bronze Insert Ball Joint Rod Ends. An oil-impregnated bronze insert reduces the need for lubrication and provides corrosion resistance. All rod ends have a zinc-plated steel housing and a chrome-plated steel ball.

I'm thinking #3...

 

[Poboy kartman]

Because I watch too much F1... I don't know what camber will work the best with race tires on ultralight go-kart, hence I want to be able to adjust it.

And just how from this hub design did you came to the conclusion that I'm NOT going to do the correct ackerman geometry??? I don't really need to study ackerman thread to learn about it. Already spent way too much time studying things in university.

To quote "McCloud" in my best southern accent- " ...They're ya go....". My point exactly. What you are doing is (in some instances) ignoring the resources easily at hand and persuing self inflicted problems.

To put it more clearly- you want to re-invent the wheel. But you want to set the benchmark as a square stone wheel. Naturally- the door for improvement is wide open. .....an oval wooden wheel is a great improvement.

But if you research the latest and greatest of the existing ideas from racing and aerospace and actually have a better idea, that's different.

Have you really compared weights and design/strengths/ weaknesses (not to mention costs) against your overly- educated musings?

Has that education and your obviously superior intellect over us poor dumb DIY's become so great that you need not consider decades of hundreds of thousands of people who's livelihoods depended on making the lightest, most dependable components for drag racing and aerospace?

Yeah......Tell ya what fella- you so dadgum smart and got all the answers.....why DON'T you know what camber you need? And if you DO need to adjust it. .....is that heim joint lighter than plate aluminum?

No- Given a contest with all the parameters defined- I could build a lighter kart with stuff I got laying around. .....

 

[vlad]

I'm not quite sure why are you being so negative in my thread... But if you want to build another ultralight go-kart - I welcome the idea.

 

[itsid]

Well vlad,
I think what Doug is trying to say:
If you don't read the thread he recommended, you don't know why he recommended it.

Let me explain:
you indeed "overengineered" because of the misconception that it would make sense for a kart like yours to have adjustable camber.
(it doesn't.. that's exactly the overengineering he was talking about)

KPI should be set according to the wheel-width (imaginary line of the kingpin ends in the center of the wheel looking from the front)
Then your camber (steering wheel straight) is perfectly safe at 0°,
everything else is corrected with the steering, camber will increase/decrease for both wheels in every corner.

This is not a race kart you build so there will be no difference if you set it up with additional camber (positive or negative) when cornering at the speeds we're looking at.
So, I don't think you can loose traction on the front wheels in a corner anyways
(that is, if everything else is set up correctly too (Toe, Caster and Ackermann))

And, if you -like you said- learned all that stuff in university already,
then there is indeed no need to read said thread,
but there wouldn't have been the need to ask about it,
or for Poboy to send you to the thread
or for me to explain why Poboy wanted you to read the mentioned thread

So, although I don't actually like the bitter taste of Poboy's last posts,
I see what he wanted you to understand

'sid

 

[vlad]

I didn't do the in-depth engineering in university, as it was far from my profession. Just the basics. The bracket design with rod ends is the simplest way for what I'm doing anyway. Adjustable camber is just a freebee. I know that go-kart tires can wear very differently. So it's an interesting idea to see how camber will affect tire wear.

As you can guess, this little project is not a necessity to give my kids a transport to be able to go to school. And not even a way to give them a toy. Plastic electric cars from china will be way cheaper for that. I just like doing things nobody done before. My own way. For the fun of it. Like Kelly with his Kart Rods, only totally different.

 

[itsid]

I see...

It's okay to just want something on your build for no other reason than to have it,
like adjustable camber in this case.
but that wasn't too obvious (well not for me that is)
I had the impression that you thought you needed it in some way or another.
(you don't! not even for tire wear)

And I think that might have been part of the confusion here.

Anyways, you want it, and I think we all can deal with that
How about this:

get premade spindles and make the holes of the mounting bracket quite large,
large enough to fit a steel retainer with a flange inside make an offset hole for the kingpin in both of them,
and by turning the retainers you can adjust camber and caster up to a certain degree.

'sid

 

[vlad]

The problem with pre-made spindles is that my "frame" is so close to the ground - the center of the wheel is higher that the top of the pivot hole part. They don't really pre-made spindles like that. Hence the whole design quest. Which I like anyway. And it looks like I even find a neighbor who can help me made them!

 

[Poboy kartman]

The problem with pre-made spindles is that my "frame" is so close to the ground - the center of the wheel is higher that the top of the pivot hole part. They don't really pre-made spindles like that. Hence the whole design quest. Which I like anyway. And it looks like I even find a neighbor who can help me made them!

That is exactly where you lost me and why. They DO make spindles like that. If you had simply explained the problem and asked for help the wealth of experience and knowledge could have given you many options. Instead you "solved" the problem by creating more. I'm sure that you and Pat will get it figured out in the end. I have my doubts as to wether the end results will be worth the effort.

I see more flaws in your design than ingenuity. If you look at the pic you posted of a spindle- you will notice that the bottom is a piece of heavy steel. This is what carries the load. You want to replace that with a heim joint. You don't have any provisions for spacing the pivot point out away from the frame. So you are going to be placing a larger load on a substitute part not up to the task. You don't have any support for the top heim- you'll need a gusset at least. The whole point is that if you had approached this as a simple problem based on proven kart design and thought about the consequences of each change more carefully, you most likely would not be headed down this path.

I can appreciate the urge to do something different. But I can also see you go the long way around and ignore any advice that doesn't fit your pre-concieved notions- regardless of whether they are viable or not.

 

[itsid]

at least get some 80/20 sidewalled corner brackets for the top and bottom ...

otherise I think it'll be too weak.

'sid

 

[vlad]

That is exactly where you lost me and why. They DO make spindles like that.

Link to the website selling them would be good here. As in a few weeks of browsing ebay and internet I didn't see any.

I see more flaws in your design than ingenuity.

Thank you for your directness. Good thing I never claimed anything I do to be ingenuine.

If you look at the pic you posted of a spindle- you will notice that the bottom is a piece of heavy steel. This is what carries the load. You want to replace that with a heim joint.

Actually top heim joint is what carries the most of the load. Bottom part only carries radial load. Neglectable in my case. That's why it can be made out of pretty thin ALUMINUM.

Here's the link to that aluminum L bracket in the picture:
http://www.bmikarts.com/BadMax-Caster-Block-Front-Right_p_1310.html

 

[vlad]

at least get some 80/20 sidewalled corner brackets for the top and bottom ...
View attachment 44569
otherise I think it'll be too weak.

'sid

I was thinking about it. I guess I can always add them if I see part failing.

 

[itsid]

I was thinking about it. I guess I can always add them if I see part failing.

Well.. if a part fails it's most likely too late already
Those cost practically nothing, but I'm sure as soon as you and Pat get in contact he'll know what to do

'sid

 

[Poboy kartman]

Well.. if a part fails it's most likely too late already
Those cost practically nothing, but I'm sure as soon as you and Pat get in contact he'll know what to do

'sid

My thinking exactly. And no- the steel plate is carrying the vertical load- the very force that heim joints are not designed to handle and one of the design flaws I am trying to get across. Your design is expecting the heim joint to carry a load 90° from what it was designed for. I can guarantee failure- the only question here is a matter of time. Personally, I think that would be very short. But again- you have it all figured out so......