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I'll be honest with ya. When you first posted with what you had, and what you were trying to do, I thought there ain't no way...too many sensors to satisfy and conditions to be met to make it happen. All I can say is it will be a he!!ava cart. Please keep posting your continuing success. I look forward to every one of your posts. GREAT JOB
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Discussion Starter · #66 ·
So I am now in the ordering parts and designing phase. I need to confirm the orientation of the engine to finish up the rear suspension and have some questions for the smarter people here. Here is my current rear design:

19393


I have the engine orientation about 45deg off of normal axis, and becuase of this the oil filter is no longer the lowest point on the engine. I just want to confirm that this should be OK or if I have to prioritize the engine being in its normal orientation. Thanks!
 

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I have the engine orientation about 45deg off of normal axis
Just my gut feel, but 45 degrees seems like a lot for a wet sump engine. Already it has to deal with road grades and g-forces (which can essentially alter the normal "level") and avoid oil starvation where you start sucking air. I don't think you're concerned so much with the oil filter placement as the oil screen and oil pan, below. The oil screen needs to always suck oil, but at the same time, the crankshaft can't splash "too much" or you blow seals and froth (which is why you can't just overfill to submerge the screen) -- it's a balancing act. You probably want your drain plug near a low point as well (along with the oil screen).

PS one other thing to keep in mind, as a go-kart, the engine will experience sideways g-forces in the oil pan that don't exist on a motorcycle (motorcycle g-forces are always "down" when riding, even when turning!) -- so it might be good to restrict the other dimensions of the problem to be more "conservative". :)

PPS I would think your top priority would be keeping the weight low, which is probably how the engine was designed in its original orientation? Could it possibly fit in front of the rear wheels? I'm curious, have you weighed the engine? How does it compare to a rider or the whole kart?

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Now I find myself wondering if a dry sump conversion might be possible...

Motorcycle Engine Dry Sumps - High Power Media

The biggest differences in lubrication needs between an engine fitted in a motorcycle and one fitted in a car are the levels and direction of forces the oil is subjected to. Notably motorcycles lean, in the case of racing bikes very heavily, during cornering. This means the oil is subject to the same forces as oil in the sump of a car, but the orientation of the bike means it remains in the bottom of the sump, rather than being pushed up the sides as it is in a car. Because of this, the oil pick-up system will be optimised to operate under these conditions, so when placed in a racecar (which does not roll) oil starvation and surge can become a problem. The other issue is from a packaging perspective, as standard motorcycle sumps tend to be very deep, which is less than ideal for attaining a low centre-of-gravity height. A lower-profile sump is therefore often desirable.​

If you keep reading, they also explore using baffles, which might help with the sideways g-forces...

Also:

Dry Sump Systems | West Performance Ltd - Manufacturer/Supplier for Motorcycle and Motorsport Performance Parts (west-performance.com)
Motorcycle | Dailey Engineering

If the scavenger pump is electric, this seems almost within the realm of reason...
 

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PS one other thing to keep in mind, as a go-kart, the engine will experience sideways g-forces in the oil pan that don't exist on a motorcycle (motorcycle g-forces are always "down" when riding, even when turning!) -- ..........
Not exactly. Side-to-side maybe but not fore and aft. I regularly record accelerations of 1g and braking of 3g. 1g is equal to 45 degrees. Not sure about 3g. :)

But I’ve never had the pan off to see exactly how it’s designed to handle this situation.

And..... I’m pretty sure the sump is separated from the crank. Looking from the clutch side there appears to just be a big hole for the oil return.

Photo is bottom case half with pan removed. The oil return hole at top is by the clutch. I think some people call this a semi-dry sump design.
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Not exactly. Side-to-side maybe but not fore and aft. I regularly record accelerations of 1g and braking of 3g. 1g is equal to 45 degrees. Not sure about 3g. :)
The go-kart, going around a simple a horizontal circular track, will likely experience 1G sideways (before slip), in addition to 1G down -- which would pull the oil to a 45 degree plane against the outside/bottom of the sump. That can be sustained indefinitely, unlike braking and accelerating g-forces which are by definition transient.

A motorcycle, going around that same track at the same speed, can experience the same 1G (before slip), but since it is leaning at 45 degrees, the oil is still on a horizontal plane relative to the sump -- it just happens to "weigh" 1.414 grams (force) per gram (mass) towards the tires.

So the motorcycle problem is just keeping the "transient" sloshes in control, not the indefinite ones, which is typically accomplished with just the sump shape or possibly baffles. The go-kart problem (like the racecar problem) is harder -- which is why racecars often have dry sumps with multiple scavenge pumps (so they can turn left and right, indefinitely! :)).

I don't believe you can get 3G braking without very very sticky tires (i.e., coefficient of friction/grip much greater than 1) -- rubber on road usually has a maximum coefficient of friction/grip of 1, affording 1G of acceleration or deceleration, which is why the published stopping distances at 60mph are typically 120 feet or so for motorcycles.

If you stopped at 3G, you could stop from 60 mph in 40 feet -- I've never heard of that but would love it if it were true! (Not to mention the wheelbase would have to be very long or the cg would have to be very low to prevent the bike from endo'ing at those deceleration rates -- I think the same 72 degree number applies to them, below.)

Here is the calculation for 1G acceleration or deceleration -- t = s/a:

> 60 mph / gravity ? second​
= 2.73512 seconds​

And d = (1/2) a t^2:

> 0.5 * gravity * (2.73512 second)^2 ? foot​
= 120.345 feet​

For the record, 3G would be 72 degrees:

> atn(3 / 1) ? degree​
= 71.5651 degrees​

And..... I’m pretty sure the sump is separated from the crank. Looking from the clutch side there appears to just be a big hole for the oil return.
Nice.

We're still hoping to get the crank open this year but have not done so yet, so I'm actually basing my guess on a 1975 KZ400 with a 360 degree crank and a chain driver counter balancer! :)

-- Rich
 

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PS

I think some people call this a semi-dry sump design.
Which would probably be ideal for a go-kart!!!

But I still wouldn't tilt the engine 45 degrees off its normal orientation... :)
 

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It's really hard to know what you are measuring there -- you could have bumps (i.e., vertical forces on the tires) or fork bounce or even engine or road vibrations interfering with the measurement of lateral forces from the tires.

If you have a 3-axis sensor, it may have to continually recalibrate its version of "down" to filter those out -- it's hard to know...

If your software has a low-pass filter (or if you mount the sensor in foam or on the axle?), you might get a more accurate picture...

I'm just going by the tire material -- 6+G can't be going (laterally, anyway) thru the tires unless they are very very very sticky...

Have you measured your stopping distance from 60mph? That's a great low-pass filter.
 

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We never stop on a race track. And when my Dunlop slicks are at 180 degf they’re pretty **** sticky 😂
 

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Well, we're certainly getting off topic, but if green is your GPS speed (?), it looks like your max acceleration and deceleration (positive and negative slope) are pretty close to the same? I can only guess you're somehow measuring vibrations which are filtered out (by suspension, etc.) before they get to the contact patch?

I am pretty certain even sticky tires (short of nascar?) don't exceed coefficient of friction/grip of 2 -- but that's all pretty secretive:

In fact a modem slick typically has a coefficient of friction around 1.8.​

Regardless of grip, I don't believe the geometry of the bike can support those G numbers -- i.e., it will endo first -- you have a wheelbase of 53 inches -- to decelerate at 6G, wouldn't your center of gravity have to be below and/or behind the rear axle?

Back to the topic, I think the go-kart has to be able to sustain side-to-side g-forces indefinitely, unlike a motorcycle, so it's probably best to mount it conservatively near its design center, if possible, rather than at a 45 degree angle from it. :)
 

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Ignore the peaks as anomalies of course but the data is what it is whether you believe it or not.

But back on topic, these motors aren’t an open oil bath sump like an old 327 Chevy small block. The sump is enclosed such that slosh doesn’t appear to be much of a problem.
 

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Discussion Starter · #78 ·
Hey everyone. Its been a while and I designed and built the vehicle. Just started engineering school again so im pretty busy but im aiming to finish it up in the next few weeks. Heres a preview:

Tire Wheel Plant Automotive tire Motor vehicle
Tire Wheel Plant Automotive tire Vehicle
Tire Plant Wheel Automotive tire Motor vehicle


Will post more details and videos once done :) thanks again for everything!
 

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Did you skip the class about center of gravity. Better put some wheelie bars on that sucker. 😂
 

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It does make me think "wheelie", as well -- ideally you want your weight low to the ground, preferably in front of the rear wheels.

I'm curious, have you weighed the engine? How does it compare to a rider or the whole kart?

Either way, I am sure this is a hugely fun and educational experience -- it is awesome to see your progress!!!

I'm excited to see what you do for linkages and stuff -- I cant imagine the challenges!

Is there just one brake on the rear axle? No brakes on the front?

(If so, having the weight behind you may be helpful -- but you may well need a wheelie bar as @Duckman said -- just take it slow, as if anyone needs to say that with 45 wild horses behind you!)
 
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