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5 hours ago, mocbuild101 said:

Nice, but I can't help thinking that all that weight will slow it down - 1080gm is very heavy!

And you also have the same 2:1 gearing that I used in my 670gm car: - yes, you have 4 motors, but they aren't fully powered.

 

 

14 hours ago, TechnicSummse said:

 I will redesign and lighten everything a little bit tomorrow :D

But... 2 motors + battery-box is allready ~320g....+cables + micromotor+ 9v switch... 

There is NO chance, using 4 motors with a total weight less then 1000g.

Im pretty sure, i can reduce this to something like ~1050g. The car of @Marxpek weights pretty much the same.

 

But while finding the limits, there is allways to improve 1 thing, at the cost of something else. In this case it was reducing gears-friction vs. weight.

By the way... it seemed to steer pretty bad when i testet indoor yesterday... now i know why :D The rearwheels are to far from away from each other... i would need a differential... but no way... i wont add friction :devil:

I hope i can do some tests at the evening

 

1 hour ago, Jurss said:

Lot of mass seems behind of wheels, which will impact stability, grip not the good way. Also it will pop up the front, when starting.

 

Even if the wheel pops up at start... this wont be a problem... it could become a problem, if the front will jump up at a little stone or something while driving... then i wont be able to steer for a short time.

But i tested pushing at the battery box... it seems to be pretty ok balanced. Maybe i gonna change the battery-box-position. Thaught about that... but it fits so nice at the back :D

Edited by TechnicSummse

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5 hours ago, TechnicSummse said:

There is NO chance, using 4 motors with a total weight less then 1000g

One of my setups was under this weight , including the gps device, but the wheels had no outer support so axles started bending, bad idea.. but all of my newer setups are around 1040-1060, my current rebuild which is not done yet, will be one of the heavier models probably.

 

5 hours ago, TechnicSummse said:

But while finding the limits, there is allways to improve 1 thing, at the cost of something else. In this case it was reducing gears-friction vs. weight

Hmmm aren't these actually the same thing? , we are reducing the weight on the bearings and thus the friction, by the logic in your previous statement; weight does not influence the maximum speed (except for the added friction on the bearings), it just takes more time/track to reach the same speed and it will drain the batteries more/faster.

But what about air resistance? you go to all this friction reducing to make it twice as wide... i cannot imagine this being better, but as always the tests might prove me wrong.

5 hours ago, TechnicSummse said:

Even if the wheel pops up at start... this wont be a problem... it could become a problem, if the front will jump up at a little stone or something while driving... then i wont be able to steer for a short time

I experienced this in my front end with suspension, after a small rock or bump you have no steering when you need it most, kind of dangerous.

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9 hours ago, TechnicSummse said:

By the way... it seemed to steer pretty bad when i testet indoor yesterday... now i know why :D The rearwheels are to far from away from each other... i would need a differential... but no way... i wont add friction :devil:

 

Quote

Even if the wheel pops up at start... this wont be a problem... it could become a problem, if the front will jump up at a little stone or something while driving... then i wont be able to steer for a short time.

3 hours ago, Marxpek said:

I experienced this in my front end with suspension, after a small rock or bump you have no steering when you need it most, kind of dangerous.

My predicted problem catched me....

I was doing some testdriving... you can see the result below...

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I also shreddered a 20t gear while i tried to brake... it just slipped and lost some teeth :D

The Machine

I will rebuild with wheels closer to each other again.... :(

 

3 hours ago, Marxpek said:

Hmmm aren't these actually the same thing? , we are reducing the weight on the bearings and thus the friction, by the logic in your previous statement; weight does not influence the maximum speed (except for the added friction on the bearings), it just takes more time/track to reach the same speed and it will drain the batteries more/faster.

But what about air resistance? you go to all this friction reducing to make it twice as wide... i cannot imagine this being better, but as always the tests might prove me wrong.

I have the feeling, friction is the key... since i testet some streamliner-design without any good result. But the faster we are driving, the more important air-resistance will become.

Since The Machine 's steering did not work, i have to go another way again anyway :blush:

Edited by TechnicSummse

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Sadly.. a familiar image there... maybe I jinxed it..

Steering has always been my biggest problem, any small over correction might destroy the car, finding a track without a curb might help, i assume you crashed into that?

Did your speed computer survive? i noticed it already had bad wires before (just like mine). 

Streamlining can never hurt.. also resistance / air friction

 

 

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Try to find better apshalt, or even concrete track. This seems pretty "rocky". For car it is OK, not for Lego speedster.

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17 hours ago, TechnicSummse said:

I was doing some testdriving... you can see the result below...

:cry_sad:

I have had a few crashes with my car too, but nothing that bad has ever happened!

I have also noticed that the center of gravity is very high - just like my very unstable car.

 

Edited by mocbuild101

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15 hours ago, Marxpek said:

Steering has always been my biggest problem, any small over correction might destroy the car, finding a track without a curb might help, i assume you crashed into that?

yes...:cry_sad:

15 hours ago, Marxpek said:

Did your speed computer survive? i noticed it already had bad wires before (just like mine). 

Wires are bad allready long time, i think since the first crash. But evrything is fine... maybe i gonna add some silicone to the computer soon.

15 hours ago, Marxpek said:

Streamlining can never hurt.. also resistance / air friction

If streamlining means to add more weigt, or fragile construcitons... it can be something negative... :D

 

7 hours ago, Jurss said:

Try to find better apshalt, or even concrete track. This seems pretty "rocky". For car it is OK, not for Lego speedster.

Im looking for one.. but this isnt really easy... the track should be close to my house (~10-15min with a car)

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22 minutes ago, TechnicSummse said:

Im looking for one.. but this isnt really easy... the track should be close to my house (~10-15min with a car)

What about autobahn ? :pir-grin:

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2 hours ago, TechnicSummse said:

Wires are bad allready long time, i think since the first crash. But evrything is fine... maybe i gonna add some silicone to the computer soon.

I would recommend completely replacing the wire - if you can...

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2 hours ago, mocbuild101 said:

I would recommend completely replacing the wire - if you can...

I think i will try this with mine, i could make a tutorial video on it maybe. but might take me some time...

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42 minutes ago, Epic Technic said:

Only if he wants to become roadkill... 

Yes, especially with the 1000+ Hp cars flying by.

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A few comments, from someone with very little idea:

- at the speeds you are going, aerodynamics do little, compared to power and weight.

- I think you could do something quite different with measuring and solve a few problems.

- if you ran over a measured course with speed up and slow down zones, then you could lose the GPS, which will save weight, but instead you need two very accurate, connected timers.

- this means you could move inside, to a gym or something, reducing hazards

- with the better runoff, you can potentially have no steering at all, and just do lots of runs instead.

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In which direction does this thing go? Are the big wheel in the front or the small wheels? How does the steering work?

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14 minutes ago, nicjasno said:

In which direction does this thing go? Are the big wheel in the front or the small wheels? How does the steering work?

Steering can be seen here:

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So if the front whee is that small and has no suspension, it is no wonder that at speeds over 20kmh very big forces start to act on it. I would use a bigger wheel (preferably the same as for the driving wheels and some suspension. You can get away without suspension ony on a perfecly smooth surface, like in a gym or in a parking garage. Everywhere else you need suspension.

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6 hours ago, nicjasno said:

So if the front whee is that small and has no suspension, it is no wonder that at speeds over 20kmh very big forces start to act on it. I would use a bigger wheel (preferably the same as for the driving wheels and some suspension. You can get away without suspension ony on a perfecly smooth surface, like in a gym or in a parking garage. Everywhere else you need suspension.

The importance of this point can't be under-rated.  I respect all these recent projects trying to go faster, set records, etc., but with so much focus on the design of the machine I am wondering if there is tons of stuff being missed by not considering factors NOT machine-related.  The surface in which one races being one of these..... and makes a huge difference.   the most recent pictures show a  surface that is so very bumpy.  Remember, real-life land speed races of the fastest cars on earth took the time and effort to have the records set on surfaces that are supposed to be the flattest on earth.  Like salt flats or something......

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4 hours ago, nerdsforprez said:

The importance of this point can't be under-rated.  I respect all these recent projects trying to go faster, set records, etc., but with so much focus on the design of the machine I am wondering if there is tons of stuff being missed by not considering factors NOT machine-related.  The surface in which one races being one of these..... and makes a huge difference.   the most recent pictures show a  surface that is so very bumpy.  Remember, real-life land speed races of the fastest cars on earth took the time and effort to have the records set on surfaces that are supposed to be the flattest on earth.  Like salt flats or something......

We talked allready about this... evryone of us would like to have a 300m gym or something to drive in... but you have to take, what you got...

And i am designing my wheel-setup as good as possible to my track. In a gym, i could use a pulley-wheel as front-wheel... but this would never work at my current track.

11 hours ago, nicjasno said:

So if the front whee is that small and has no suspension, it is no wonder that at speeds over 20kmh very big forces start to act on it. I would use a bigger wheel (preferably the same as for the driving wheels and some suspension. You can get away without suspension ony on a perfecly smooth surface, like in a gym or in a parking garage. Everywhere else you need suspension.

Suspension does not make sense... we all tested this allready. Since we mostly use just 2 beams at the frontend, we got something like a suspension there... the beams are bending, and acting like a spring. At the rear... there is a lot of ballooned rubber on the wheels, wich also gives some suspension.

A bigger sized but thin frontwheel would be better... sure... but this would mean a huge construcion to keep it in place. The bigger the wheel, the more you have to build arround it :(

My frontwheel is defenetly a compromise... its relativly small and as big as i could use it with my steering setup.

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20 hours ago, nicjasno said:

So if the front whee is that small and has no suspension, it is no wonder that at speeds over 20kmh very big forces start to act on it. I would use a bigger wheel (preferably the same as for the driving wheels and some suspension. You can get away without suspension ony on a perfecly smooth surface, like in a gym or in a parking garage. Everywhere else you need suspension.

I think that suspension is not needed because of the beam flex we have in our cars, but I do agree that bigger wheels would help with rolling resistance - take this (said in another topic) for example:

On ‎5‎/‎07‎/‎2017 at 6:25 PM, vectormatic said:

fuel1.jpg

air resistance only overtakes rolling resistance in that chart at 60 km/h, at 40 the rolling resistance is twice as large as drag.

 

 

13 hours ago, nerdsforprez said:

The surface in which one races being one of these..... and makes a huge difference.   the most recent pictures show a  surface that is so very bumpy.  Remember, real-life land speed races of the fastest cars on earth took the time and effort to have the records set on surfaces that are supposed to be the flattest on earth.  Like salt flats or something......

Yes - that's why we are constantly looking for better surfaces to test on - but we can only use what we have...

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After my last crash, i redesigned the car again, with some good results so far.

A 37,3 kph-run was the best result today. But im really really sure, it could be faster on a longer track. It seems at the end i will also need a GPS-devce to get a usefull speed-graph.

This is pretty much the same design then my 38,7kph-car, but with some improvements on stability and a totally new gearing.

 

Total weight including speed computer -> 1046g

Batterybox attached between the wheels, but behind the axle

Gearing: -> ???? Who can guess it? (you have to think a bit outside of the box :devil:) -> The one who guesses it first, gets a cookie :grin:

-> If you can guess it, please post it in a spoiler ;)

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10 minutes ago, Marxpek said:

1:1.8 from the fast output?

Please post gears, and not just ratios ;)

But you should know 1:1,8 would not lead to 37kph :D

Edited by TechnicSummse

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yeah just noticed that was not an option.. must be 24:12 then?

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