A level technology go kart project (feedback please)

[KGoodall]

Hi there, this is my homemade go kart that I built alongside another student as part of our A2 coursework. It is basically finished, just requiring a chain, brake line and throttle cable to be run to finish it off.
I would just like some feedback from you experts on how well you think it satisfies my 'form' spec. point: "Fit in the track environment and be attractive to the target market (upstart motorsport teams/privateers)"
Any comments would be appreciated and feel free to ask any questions! Thanks!

 

[itsid]

it needs a floorpan, front and rear bumper at least
It could use some nerf bars too.

For me the engine is on the wrong side of the kart.. (used to have it right of me)
And the frame... oh hmmm *shrugs*
all the welds for no other reason than a missing bend,
I personally don't like very much,
it looks unsafe, and rather short (more like a cadet or bambino kart)
If that's a 50mm rear axle your tubes are too small IMO,
the steering geometry is WAY off,
about everything: camber, caster and Ackermann...
so it'll not be competitive in any way.
I'll better stop now
So if you ask for a target market "upstart motorsport team", they will take a laugh and go.
Sorry, that might sound rude.. I don't mean to be, but it's nowhere near a racing kart.
They will pick up a last season frame for a few hundred bucks and have a much better start.

As a funkart, to burn some rubber in the neighbourhood with a couple of friends...
That will work
Race track... I don't think you could get that thing approved

'sid

 

[OzFab]

Yeah, that's pretty much what I was gonna say but, with a little more tact...

FYI, a bend is much stronger & more reliable than a cut & welded angle

Don't get disheartened, it's not a total loss, with a bit more R&D, it could be a good kart...

 

[landuse]

Yeah. As a fun kart it is killer, but as a race kart you are going to have to do a bit more work. You are definately on the right track though

 

[KGoodall]

Ok I didn't explain myself very well there. I think itsid you've misunderstood what I was going for, we never built this kart to be mass or even batch produced, it is a prototype! It will never be raced or homologated so I'd never expect anyone to buy one. (I have a racing kart and I agree this would never be anywhere near as good) As far the geometry is concerned it has copied exactly from a 115cc TKM extreme chassis kart so how that is wrong, you tell me... Yes the engine is on the opposite side to most normal karts but IF IT WAS ON THE OTHER SIDE IT WOULD GO IN REVERSE!! Yes I could turn it around but it'd be even more "unsafe" as you'd run the risk of shredding your arm on the sprocket!!
I am very aware bending would be far stronger and more competitive however I did this at school where these facilities do not exist so this was the next best option!
Sorry for the mis-understanding and thanks for the advice anyway!

 

[landuse]

Ok I didn't explain myself very well there. I think itsid you've misunderstood what I was going for, we never built this kart to be mass or even batch produced, it is a prototype! It will never be raced or homologated so I'd never expect anyone to buy one. (I have a racing kart and I agree this would never be anywhere near as good) As far the geometry is concerned it has copied exactly from a 115cc TKM extreme chassis kart so how that is wrong, you tell me... Yes the engine is on the opposite side to most normal karts but IF IT WAS ON THE OTHER SIDE IT WOULD GO IN REVERSE!! Yes I could turn it around but it'd be even more "unsafe" as you'd run the risk of shredding your arm on the sprocket!!
I am very aware bending would be far stronger and more competitive however I did this at school where these facilities do not exist so this was the next best option!
Sorry for the mis-understanding and thanks for the advice anyway!

Whao!! Dont get the wrong impression that we are raining on your parade. You have made a kart that you can be proud of. Not many people would even attempt what yu have done.

However....you asked us to comment on your spec, which was how it would fit in the track environment. This is what we have been commenting on. It would not fit into a race environment as it sits now. That is what we were trying to say. If you post on a forum asking for comments, you are inviting people to give their opinion, good or bad.

As for the engine, if it goes on the other side you would just have to use a jackshaft, but I see that it was just easier where it is now. As for the bending of the tubing, we were also commenting on it in the context of a race environment. We had no idea that you didn't have the facilities, so you cannot say that our comments are harsh. They are all based on the information that you gave us, and what we can see in the pics

Anywhoo.....

 

[fowler]

Ha chill

Even though itsid was a bit rude lol
All vaild stuff though

Easy to forget your commenting on others hard work when your over the net


But I see what your doing
I had to do the same thing during school
It's just the final report/power point of the project isn't it

I can't help though
I was rubbish at it

The engine in the other side is interesting
Never seen it
Everyone runs there's on the other side because that what the prifesionals do
But why not

U have managed to eliminate the hazard of the chain and the exhaust
And the exhaust actually faces backward
Put that in your report for sure

Add a floor pan and a cross in the front end

 

[KGoodall]

I understand and expected to receive a lot of the points mentioned such as bumpers and a floorpan, however the way 'itsid' went about it was wrong. Admittedly I gave the wrong impression initially and asked the wrong question however I don't understand a number of his points as they appear to be drawn from no where. What is the basis of his analysis of the geometry and tube thickness? As I stated earlier it is exactly the same as a competition kart and the tubes are actually slightly thicker.

 

[KGoodall]

Ha chill

Even though itsid was a bit rude lol
All vaild stuff though

Easy to forget your commenting on others hard work when your over the net


But I see what your doing
I had to do the same thing during school
It's just the final report/power point of the project isn't it

I can't help though
I was rubbish at it

The engine in the other side is interesting
Never seen it
Everyone runs there's on the other side because that what the prifesionals do
But why not

U have managed to eliminate the hazard of the chain and the exhaust
And the exhaust actually faces backward
Put that in your report for sure

Add a floor pan and a cross in the front end

Yeah its the portfolio. Thank you though, that was far more helpful and constructive, more what I was looking for!

 

[KartFab]

I think itsids comments have the most truth to them. Sometimes the truth can be harsh, it is how you react to it that makes it a positive or a negative.

I don't know much about race karts, but I thought the engine being on the right (along with the rider shifting his weight) will put more weight on one wheel and allow the frame to flex a little bit for better cornering.... I could be completely wrong though.

 

[Poboy kartman]

I don't think there was anything rude about Itsid's post. Brutally honest yes. The OP asked for opinions based on certain criteria and got one. I'll take honesty over false flattery every day.

I get rude occasionally- but more often my directness is mistaken for rudeness. ......

 

[exenos]

I think itsids comments have the most truth to them. Sometimes the truth can be harsh, it is how you react to it that makes it a positive or a negative.

I don't know much about race karts, but I thought the engine being on the right (along with the rider shifting his weight) will put more weight on one wheel and allow the frame to flex a little bit for better cornering.... I could be completely wrong though.

The engine being on the right would be beneficial for a oval track to have more weight on the out side of the kart but in a road style course that has both left and right hand turns it makes no difference IMHO as long as the kart is balanced.

KGoodall,

I have to agree with every one on the fact that while sid's comments may seem harsh they were meant in the best way. He was working with a few pictures and no other information and just made the best assumptions he could. The steering geometry does look off at first glance and it does look a bit short to be safe at speeds

 

[firemanjim]

With the engine on that side, you gotta run a clockwise (right hand turn ) track.... Or you run the risk of flipping it.....

 

[itsid]

...As far the geometry is concerned it has copied exactly from a 115cc TKM extreme chassis kart so how that is wrong, you tell me...

Well first of all, as far as I can see your control arms are at an angle too big to achieve propper Ackermann steering, the kingpin inclination seem to be unequal on the pictures (I don't think it is) but it's at least too little for the way you mounted the front wheels.
your caster needs another two or three degrees at least I'd say to have a good straight running kart,
Well the camber seems to be zero that looks okay, but for spindle arms that long the tilt will be odd when cornering.
(you want the wheels MUCH closer to the kingpin)
If your race kart has that exact same steering geometry,
I owe you a beer.. but I doubt it!

... Yes the engine is on the opposite side to most normal karts but IF IT WAS ON THE OTHER SIDE IT WOULD GO IN REVERSE!! Yes I could turn it around but it'd be even more "unsafe" as you'd run the risk of shredding your arm on the sprocket!!

Well that's why god send us chain and exhaust guards for karts
TKM rules state that the engine MUST BE at the right hand side btw

I understand and expected to receive a lot of the points mentioned such as bumpers and a floorpan, however the way 'itsid' went about it was wrong. Admittedly I gave the wrong impression initially and asked the wrong question however I don't understand a number of his points as they appear to be drawn from no where. What is the basis of his analysis of the geometry and tube thickness? As I stated earlier it is exactly the same as a competition kart and the tubes are actually slightly thicker.

I can't tell for sure what tube sizes you chose of course by just looking at the pictures.
I can only guesstimate the numbers.
Saying you have a 50mm rear axle (about the biggest dia I know)
that tubes look like ~20-22mm max.
which is way too small for a race kart;
race karts have 28-35mm, based on FIA regulations AFAIR.
-------
those are to be met to get MSA yearbook approval, and that's needed to run TKM class karts btw
-------
And most important it's most likely a better grade steel too

But again, this kart looks short.. very short for an adult kart;
maybe that's the problem Cadets, Bambini and junior karts are not meant to take and carry the weight of an adult of course, thus the tubes can be smaller (as small as 25mm on some karts and classes)

Anyways...
You've come to the right place,
this forum can and will provide all the help you need to make your idea not only safer but also better handling, and if you want faster too

But you need to uncross your arms and listen sometimes

'sid

PS Sorry for being harsh, I didn't meant to

 

[fowler]

With the engine on that side, you gotta run a clockwise (right hand turn ) track.... Or you run the risk of flipping it.....

Aint most tracks proper tracks
Unless they're dirt

It's not a nascar

 

[exenos]

I'd say 95% of ovals ( and regular tracks to )in North america are CCW left hand turns. Probably has something to do with the throttle being controlled by the right hand in most power sports and its easier to control it while turning left.

 

[firemanjim]

?? I don't know what you guys across the pond run?

 

[KGoodall]

I can't tell for sure what tube sizes you chose of course by just looking at the pictures.
I can only guesstimate the numbers.
Saying you have a 50mm rear axle (about the biggest dia I know)
that tubes look like ~20-22mm max.
which is way too small for a race kart;
race karts have 28-35mm, based on FIA regulations AFAIR.


But you need to uncross your arms and listen sometimes

Agreed, yes I got defensive too quickly and much of your advice was correct. However the reason for that is the fact that you were wrong about the tube diameter. It is actually 33mm diameter Steel with a 3mm wall as opposed to my other kart which I believe is 32mm diameter chromoly with a 2mm wall. So I apologize for overacting but it would have been beneficial to clarify.

The control arms point is 100% correct they are too steep but it is the incorrect position of the steering wheel rather than anything else that dictated this. The kingpins are at the same angles both sides I can assure you and are honestly the same inclination on my other kart (I literally copied it). The spindles are taken from that too so I'm not quite sure what you mean about the wheels being too far away?

I'm sure you're right about the TKM rules dictating engine side but costs mean I am using a generator motor that spins the other way and in trying to keep the width of the kart narrow enough (so it matches the other one) I had to mount seat/engine this way around (even with a guard it'd just be too close). As far as cornering goes, 'exenos' has got it right I think in that it doesn't matter which way around it goes so long as the kart is balanced. Without corner-weighting it'll be hard to tell but I suspect it wouldn't be great if I'm honest. Still it's useful to know that rule and I will include it in my report for sure!

Could you just explain what you mean when you say it looks too short? The wheelbase is once again copied from my racing kart that is a full sized adult chassis.

Thanks again for your help I do appreciate it even if I don't sound like it

 

[itsid]

Ah so the tubing is much bigger than I thought... good!

Ackermann steering goes basically like this:

As you can see, the control arms
(or precisely a drawn line from each kingpin through the mounting point on the controlarm)
should point to the center of the rear axle.
that way it's easiest to steer.

It appears your control arms point to the opposite rear wheel.

The best amount of grip can be achieved if the kingpin inclination points to the center of where the wheel is in contact with the road.
a small offset is okay as long as it's still inside this contact area.
(tire wear will be uneven, but who cares)

yours are off by a fair amount, also your front wheel should be as close to the kingpin as possible to have the best possible handling.

The KPI doesn't seem to be big enough, even if you mount the wheels without spacers.
But it's hard to tell for sure with the pictures we have atm.
At least loosing the spacers could improve the handling by a good amount
Yes, race karts have spacers to adjust the front track width or set it off a bit,
but to set up the basic frame geometry loose them

And by too short I mean exactly that..
front to rear axle distance or to say in in driver comfort terms:
backrest -> pedal distance
Maybe the images are distorted *shrugs* maybe you can ask a friend to sit in it or take a picture while you sit in it

Now, a typical front track is 46" (outside to outside of the wheels) a typical rear is 50"-55";
wheelbase ~41"
your's look closer to be in the 35" range
Again, might be the pictures (or my eyes for that matter)

'sid

 

[KGoodall]

And by too short I mean exactly that..
front to rear axle distance or to say in in driver comfort terms:
backrest -> pedal distance
Maybe the images are distorted *shrugs* maybe you can ask a friend to sit in it or take a picture while you sit in it

Now, a typical front track is 46" (outside to outside of the wheels) a typical rear is 50"-55";
wheelbase ~41"
your's look closer to be in the 35" range
Again, might be the pictures (or my eyes for that matter)

'sid

Yeah the ackermann is wrong I changed the spindles for cheaper ones than I used for mock up and as such the angles are out.

Its probably not as small as you think it is, the wheelbase is 44 inches, rear track 50 inches and front 42. Its not very spacious for the occupant but at the moment it only needs to fit me and I'm not huge!

As for the KPI I'm not sure where about the line ends up but I will check for sure