Frame good or deathtrap?

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nak18

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Is the design below good?

I plan to use something similiar to this design, but it will on-road unless I'm travelling on a gravel road. If I go off road it will be to get somewhere speed not great than 15mph. Onroad, I'm think about 65mph-75mph.



1.This is the First Layer:
-Do I need the highlight steel or is joining at the arrows ok?



2. Without bracing:
How good, can I go without bracing?


3.
Will this bracing prevent bending, or welds snapping from stress over bumps.
 
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B-Well

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you're gonna need one hell of a motor to do 75, and that feels like 2000mph when your an inch from the ground in an open cockpit.

my 125 shifter does around 75 and its a weird feeling even after 4 race seasons and i know its uber safe with fresh tires and bearings ect.

i personally wouldn't take a homebrew cart up past 45 due to the parts we use are not rated for high RPM
 
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nak18

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B-Well said:
you're gonna need one hell of a motor to do 75, and that feels like 2000mph when your an inch from the ground in an open cockpit.

my 125 shifter does around 75 and its a weird feeling even after 4 race seasons and i know its uber safe with fresh tires and bearings ect.

i personally wouldn't take a homebrew cart up past 45 due to the parts we use are not rated for high RPM
Click to expand...

For parts, I want to use some sandrail/dunbuggy parts.

TorqueRanger said:
Death trap in my opinion... Relying on welds in the hope not to kill yourself..
Click to expand...
Deathtrap as in Metal bending over time. Most karts are welded.
 
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TorqueRanger

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nak18 said:
For parts, I want to use some sandrail/dunbuggy parts.


Deathtrap as in Metal bending over time. Most karts are welded.
Click to expand...

No as in to many welded joints ... A piece of steel is stronger as on piece than a length with several welded joints.
 
Bluethunder3320

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maybe look for some buggy plans.

35mph in a manco single seater is pretty fast. gets kinda hairy around turns and in traffic on the road... i know yyoure not making a dinky little single seater, but you wont be much higher off the ground. 70 will feel crazy...
 
Doc Sprocket

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Nak18- are you not able to get tubing lengths that are long enough to begin with? You don't want to start butt-welding main framerail sections together!

I've gotta get on board with the other folks here- basically, your speed expectations are unrealistic. You have two choices, IMHO-

1) Rearrange your thinking, and wrap your head around 40-45MPH, tops. Less if you're building the above frame as is.

2) PURCHASE a truly suitable chassis, or COMMISSION a reputable frame-builder to build you a suitable chassis. No insult intended here, but there is absolutely no place for a fella asking questions like that at 75MPH. That's a guaranteed Darwin Award. He//, I consider myself pretty dang competent, and I would think twice about building a kart for those speeds. Not only do you have to be a terrific welder, you need to have a good working understanding of the applicable structural engineering aspects, which (again, no insult) you clearly do not. On top of that, you have to use the absolute very best componentry and materials, and your design cannot lack anything- 4 wheel braking, appropriate center of gravity and center of balance, etc.

And a parting thought- either you're building for on-road speed, or offroad ability. Any kart that could safely do 75MPH on pavement will be dead useless off road, and unless you're building a very serious sand rail-type buggy, you don't want to hit speeds like that in an offroader.
 
redsox985

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^^ My thoughts to a T. Don't build your own frame for 75MPH unless you're an engineer & welder. You want continuous pieces and not butt welded scraps.
 
OzFab

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I'm with these guys. I'm no expert when it comes to go karts but I do know a bit about metal/welding strength. Start with continuous lengths for your rails; steel tubing is not that expensive. Your current design will only end in injury (or even death at the speed you want) when the butt welds give out.
 
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Badot

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Another vote for deathrap here.

I would say don't even build a kart for 40 mph unless you have a good understanding of structural mechanics. I would also say don't build a kart in general unless you massively overbuild it (unless you have some degree or a lot of experience in vehicle frame design).

First thing you need to know - triangles. Take a thick piece of cardboard, make a square shaped tube (larger square and shorter overall tube will give you a better idea), tape it together, and then try and push the sides or corners inwards on themselves. Now take another thick piece of cardboard, make a triangle, and do the same thing. The square one was your frame at 70 mph.

Also, going out on a limb here and assuming the program is Solidworks.
 
jrmints1415

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thats what i first thought too. I vote deathtrap too because of the but welds. No matter how many gussets or bracing you put on their it would not be TOTALLY safe driving down the road at 75 mph. aim for something around 45 like everyone said that is still a lot faster then you think in a kart.
 
TeamCheap

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What else have you built?
have you built something that will do 30-40 yet?
maybe work your way up to that goal of 70+mph.

The fact that your asking is a good sign the little voice in your head is saying "deathtrap".(very smart)

I'm of the thinking that more bends less welds is the way to go.

Might be better to look for a good used race kart and go from there.
 
Bluethunder3320

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if you wanna go so fast get a race kart. a WC 250cc 2 stroke dirt bike motor (on race kart) could get you the 70mph. maybe even a 125cc
 
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