Marxpek

even if we use such a heavy gearing in which it cannot pull away on its own and then lets that work when its up to speed? then why do we gear it up at all? and even if this all is no use, i would love to be able to use a shorter track, i still did not managed to get a full speed run from my car

I feel that would be cheating.. all power should come from Lego, that way i could drag it behind the bike to 30 km/h then engage the motors with an insane gearing, and with this setup the pullback motors are not included in the actual record setting car which breaks loose from the pullback motor pusher car to get the initial speed. This is exactly what i had in mind, good luck!

Like i mentioned before: great minds think alike, it's really fun to see you are trying the exact same things as i have. I tried this pullback motor idea in the very early stages of my first racer, and found the exact same results as you have: friction and speed loss. Here is a idea for you (that i have not tried) : make a 2 stage system, the first stage being a pullback car which can break loose from the rc racer, this will allow you to use a higher gearing in the rc racer since you can start the motors when they already have some speed, while causing no extra drag or weight. Don't worry about suspension too much, in your front setup the liftarms will provide some suspension with the flex they have mounted like this and i can tell you that my attempt with the suspended front wheels was a failure, ill update my topic today. The wheel and bearings need a bit more thought, but i'm sure you will manage! Looking forward to your ideas and attempts! Keep it up!

Hmm i do not know if this is an improvement to your design, the profile seems much much higher now, cause more air resistance, also the battery box on top will make it more likely to start rolling, i liked your setup with it being in the back better. I also noticed you are using long axles where you can you axle connectors, these less likely to bend under speed, https://www.bricklink.com/v2/catalog/catalogitem.page?P=6538c&name=Technic, Axle Connector 2L (Smooth with x Hole + Orientation)&category=[Technic, Connector]#T=S&O={} any reason why you are not using these? Did you ever consider to take out the 9v switch? just switch the batterybox directly with the micro motor? would save the switch and a wire in weight. sounds about right, but don't forget that i will be able to fully power all 4 motors.. You think this is worth testing? so wide and so many frictionpoints in it for a 2:1 gearing does not seem viable to me.

Yes, exactly the same system based on caster just with 2 wheels, great minds think alike ;) you could take out the liftarms in the front and replace them with halfbeams easily to reduce friction in the front.

Good job! i'll be looking forward to see your progress here. How does your steering setup work? Same system as mine isn't it? that sportswatch looks good on the car ;D Good luck on your attempts!

How i wish this was true, I've spent about 4 hours searching for the pulley wheels, i was certain i had them somewhere, but i could not find them, it turns out they were in the box of the 8412 with the rest of it's spare parts (the b-model uses them) I have sorted my Lego, but not everything, sometimes making it hard to find (older) pieces Putting them together will make it harder to "push away" rocks since they will be pushed into the next wheel, or even wedging it in between them. it also needs more construction as they do not run smoothly when mounted in a 1 stud wide opening, the tires rub the curved halfbeams, however i do agree it should improve a bit further to get the wheels braced from the outside. wait for the right moment, the raised center is a good thing for this, incoming bikes can never get to my half and since the car is going way faster then anyone is cycling there; bikers behind me will never keep up, so i just need the road ahead to be clean, but here is always the danger of running my own bike over it, i still consider that the most dangerous. But yesterday it took me 1 hour to do 4 runs. The bent antennas do give a little bit less range, but not 80% less, but i do notice some lag on the steering when its far ahead me, i'll see into it. The weight with the new suspended front comes in at 1029 grams, and with the ZR frontwheel it comes in at 1030 grams, ready to run, including the 40 gram gps device. I am aware that a bigger wheel will give less resistance to rolling and bumps, but the size will also increase the construction and thus the weight, but i would love to hear your suggestions, but i cannot see how i can get a skinnier tire then i have now, larger yes, but more skinny? no

Little update with pictures: Today the weather was somewhat decent, so i decided to test out my new track, it is very smooth and clean, but it is very narrow because it has a raised center, dividing the 2 bike-lanes. The track is long, smooth, flat and clean, but a bit narrow and the middle raised part, shown on the right picture. After only 4 runs i ran into the middle landing on top of it partially and destroying a good section of a 40t gear, ending the test for today. I have been using this setup today: This picture has been taken after driving into the middle part, you can see the grey smooth pin, totally grind down, it had a mini wheel on it before the run, that is gone with the wind. I have been able to compare the pulley wheel + tire to the 36.8x14 ZR wheel, differences are minimal but the bigger and wider ZR wheel performs better because it is just too bumpy. Back home i had set out to reduce the weight of the front steering section which was over-designed like i always seem to do, I quickly simplified the front with the ZR wheel but when checking in at here at my topic i saw this: And i figured: pulley wheels and suspension could work, maybe even better, worth a try. So i came up with 2 new front ends, yet to be tested outdoors at high speeds (sorry for weird picture format, having a fight with bricksafe here...) Surprisingly the suspended version with the pulley wheels weights in 1 gram less than the not suspended ZR wheel, indoor tests show good results with both setups, in theory the pulley wheel should perform better, lets see what the reality says. Fingers crossed for good weather..

Don't worry, i grew used to this kind of damage :D, just sad in ended my tests. well the difference is very minimal, don't forget that the pulley wheels are way more narrow so less likely to hit small stones, but if they do, the impact is harder, and on the small pulleys the tires are a bit bigger then 2 mm (i guess 4 mm) in the end it all depends on the track. I too have only 4 half beams of friction in my rear setup with no bending of any axles, it can spin without load, without bending the axles (spinning it without load is a pretty good test for that i think, you will see the wheels start to wobble if the axles bend under speed/high forces) Front setup has been changed after today's test, basic principle is the same just lighter. I haven't been able to get the max speed from my current gearing yet (looking at the gps data speed graphic is so helpful here), all 4 runs ended with crashes or steering errors today, my new track is really smooth and long, but it is a bit too narrow, would hate to abandon it but i might have to..

Will you be using/testing it in your racer? 2mm seems rather small to me. I have just done few testruns and my gps data show a fairly consistent difference: the (2) small pulley wheels always took more track and time to reach the same speed compared to one 36.8 x14 zr (although all my runs ended in crashes). I have also destroyed a 40t gear with a crash, a good section of the teeth has been grind down when i got on the edge of my new track..., ending the tests for today.

Is it similar in design to the small pulley tire? or is it softer like a rubber band? At the moment i have put 2 small pulley wheels with rubber tire in my front end (kind of hard to get 1 centered on a axle..), roll resistance is very low, but i fear it will be too bumpy on the road outdoor, and it has just half a stud of ground clearance, which i don't really like, I will try though. That is also true, but the small radius also means there is less tooth-to-tooth contact, putting more torque on a single tooth compared to bigger gears, making it easier to slip and/or destroy the teeth. Yeah weather is a pain at the moment... I have changed the front end a little bit (lost the brace, might indeed be better in case of a crash, so the front can "split open"), and added some outrigger axles as protection, and some minor tweaks, i'll make some pictures on the updated version today as well, might even do another run to test the pulley wheels. And i'll be looking forward you see your new (crazy? ;D) idea!

I have tried this, but it would either need a much more gears or poorly braced gears, (in both cases adding a lot of friction) i'm not saying it cannot be done, but from my experience: simplicity is key here, but maybe i will give it a try again, i do love the idea.

Sorry but again, this is the tire for the small pulley wheel, we are looking for the tire that was used on the big pulley wheel https://www.bricklink.com/v2/catalog/catalogitem.page?id=688#T=S&O={} in the picture @nerdsforprez sent.

do you have a partnumber or any other information on it?

thanks, but this is the tire we already discussed for the small pulley, we are looking for a tire on the big (old) pulley, https://www.bricklink.com/v2/catalog/catalogitem.page?id=688#T=S&O={} i'm not aware it exists, but if it does i would like to know. for sure, the 8t gear is a bit weak (my racer ate a few when i tried to make a 36:8 gearing). and since it is smaller it has a higher chance in slipping gears. (but your execution was pretty good with the 8t wedged between the 2x 24t)

not yet indeed, but i have not been able to go all out with this racer yet. is it a Lego tire? i could not find any that fit this pulley wheel. It feels a little low to me, my current theoretical speed is 75,46 km/h, @TechnicSummse racer that did 38km/h+ has a theoretical 66km/h and my first steering record with 2 motors had a theoretical speed of 57,13 km/h, but it is very hard to say what works best, at least yours will have no problem accelerating, but my guess is you can gear it up further!

After doing a bit more weight and profile reduction, I managed to do 1 test run but soon after decided to stop trying, everything was still wet from the rain and when the racer ended up in the grass, the racer was all wet and muddy, so it needs cleaning and a better day first to fully test it. The acceleration surprised me a bit, so it went out of range from my controller faster then i had anticipated, losing control and power and going uphill, it still managed to go well over 35 (i'll keep the actual speeds a bit of a surprise), it is a bit hard to extrapolate the speed from the gps curve since it was a uphill ride, but there is power left for sure, At least i know my steering setup is working very good at 35km+. The steering works just as i had imagined and is causing very little drag on corrections while not pushing the car into a roll-over on relative sharp steering. P.s this is not my new track, just a decent piece of asphalt in a park near me, but this park has some up- and downhill parts so it is not really useable for me, but i wanted to do some quick tests nearby, since rain is always just around the corner here. I'll keep you informed. Is this the large old pulley wheel with a tire on it? or the smaller pulley wheel we discussed earlier in this thread? I think both would be to weak for this, but it is a good idea of course, the more narrow and the lighter the better, but we have to keep track of real world situations, like bumps or crashes or steering errors, I also have a feeling it would be very easy to loose the tire on this wheel.

You are testing the setup already? if so, what are the problems? and are the result you get somewhat consistent? And.. will your speedracer project stay hidden? you mentioned in your drift racer topic you are working on it ;D

I never saw this set in action and know very little about it, it needs a pc or a wall outlet? really no way to take it outside? or is that about the light sensor? maybe a laserpen can overcome that (if that does not destroy the sensor..?) it would be so cool to do the accurate measuring with Lego as well..

And that mindstorm setup idea you had? is that viable? i like that idea since you do not have to add anything to the car (no weight from the gps device, and no friction from the speed computer)

I don't see how being stable is a bad thing, maybe you mean rigid/stiff? I agree that is a bit on the heavy side but like i stated before, i will try to reduce the weight a bit more, but as you might have noticed, i have an (automated) habit of bracing everything, i can/will reduce the weight in the rear bracing as well. I hardly ever crash into solid objects since i only drive on tracks with grass next to them (my new untested track has the same, it's one of my demands on a track, no curbs for sure) And if i do crash into something solid, my guts tell me the 15L liftarm, the pins or the 5.5L axle will snap before the rc unit pinholes gives way, the real danger is driving over it with my bike when control is lost... that would be bad.. i tried the 37x22 in this setup as well, but they are too wide after a bit of scouting in my collection of wheels i found these to be perfect for this cause, I have considered using the http://rebrickable.com/parts/2815/technic-wedge-belt-wheel-tire/ but think it will break under the stress (maybe not on a perfect track), these pulley wheels aren't that strong, i broke a few using them as extra axle connectors on the motorcycle tire and they break easily under high stress. I also tried the wheel you are using now, its is ok but you can hear the resistance of the thread when you roll it on a hard surface, and i am not convinced having 2 bearing points in the front wheel is better than 1, you are adding an extra frictionpoint, to the system and There is some sideways motion on 2 points as well, causing more friction. I guess having 1 point with a faster spinning axle gives less resistance than having 2 point with less speed on the axles, but that is just my gut feeling, no tests were done... That would fix it indeed, but that will not make it any easier for you. Did you do any comparison with another gps device? or something else maybe?

I have added some tiny wheels on the buggy motors pinholes after taking pictures, i still need a similar solution for the front, but it really wants to stay on its wheels when driving and even when steering, this steering setup does not tilt the car like i assume your does a bit?, but yes, i will use these wheels to save the units from getting banged up too much, but they rarely touch the ground (indoors) small video on the workings of my steering: That should explain it better than words. I think you could use a better front wheel in your racer (this one "36.8 x 14 ZR" is much more "racy") than your offset thread front wheel, however mine will have to spin faster then yours at the same speed since it is smaller, maybe causing more friction, but it will have less roll-resistance, tests will have to show , but for now its raining cats and dogs here... summer in The Netherlands is great ;D That is a good idea! check if the gps is available in 1 second mode on high accuracy, (normally it is measured around every 4 seconds, not giving very accurate results on relative short runs like we do, but try it anyway if there is no 1 second mode) The buggy motors have quite a distinct sound, and you can hear when they are on their top, although its kind of hard to hear when cycling at 35 km/h.. So mostly: trial and error for me, just get the best run you can and check the results afterwards, if i can (most runs end in crashing into the grassy border of my track) i will race the entire length of my track, just to be sure, but also when you have done as much tests as I/we have, you will get the feeling for it, you can "see" the speed and I can feel how hard i have to pedal for it to keep up. Most of the time it took about 150m for me, perfectly showing on the gps data, that is very helpful to me. My last double rc unit racer needed 170m to go over 35 km/h but that one was heavy so needed a long track. Getting a good run is always tricky, any small bump or dirt on the road can cause a severe crash at 25km/h+ and there always is human error, cycling fast and controlling the racers can be a bit tricky, you kind of cannot instantly brake on the bicycle since your hands are on the controller..

It is a Brighton 100 cycling computer. http://corp.brytonsport.com/products/rider100?lang=eng

Once again there is a speed limit to break! This time the aim is 40 km/h and this time i am not alone! After i broke the 35 km/h limit, the record seems in trouble with @TechnicSummse on the horizon! He too is trying to break the 40km/h with Lego and is getting some serious results, until this day i have not broken his (unpublished record) of 38.4km/h, go check out what he does, good fun! I always tried to make my racers look somewhat good, I also tried to build them so they can survive a crash, that's all out of the window now, lightweight, low roll-resistance, all the proven concepts i will have to use here. This is fully untested, except for the steering unit, this has functioned fine on a 30km/h+ testdrive, but on my old setup with the wheel in the back. The steering setup resembles a shopping cart wheel setup, with the pivot point way in front of the wheel so it wants to go straight by itself, but it allows for accurate and low drag corrections. I might try to reduce its weight a bit more. sorry for the weird setting in the pictures, ill make better ones later on when it's final.. Now i am waiting for the right moment to do some test runs, the lack of time and the rain on days when i do have time, can be somewhat frustrating for me since i am eager to test this. I have a good feeling about this, but of course i would be glad to take suggestions and consider them. What are your predictions on it's speed? Place your bet before the test runs! ;D

I don't brake, i crash, my car was more solidly built than yours so it could take a bit of a hit without "exploding" ;D my track here has grass on both sides, clearly visible in my video's, so that's a fairly safe option, otherwise just let it run it course, that why i want 200m minimum, the downside of the grass on the sides is that it too can break the front 7L liftarms i used in the steering, i broke 4-5 total i guess when driving at speed into grass. And yes i do think the rc unit can handle reversing 2 motors, but not in the way we have geared them and with these speeds (way more force is needed to stop them, thus longer time of high current). It is very bad for the motors themselves and is always a bad idea to reverse polarity on any motor instantly especially in high torque situations. I only brake by reversing the motors when i see extreme danger to my Lego or others, like a incoming car or not being able to avoid a solid object (one side of my track has trees alongside it). I admire your guts for trying, it crossed my mind to try it as well, but after reading into it i decided to never try it...maybe what i read was right or maybe it was wrong, but i decided to not risk nearly 20 year old and hard to come by equipment But even if you fry your rc unit while doing it, it would still be a record, just make sure you film every attempt! But is that worth it knowing that someone (me) could reach similar result with a 2nd rc unit? Did you ever manage to reach the 38+ again? Do you notice any changes? weird smells (near the antenna opening after a few runs)