Doc_Brown Posted April 20, 2014 Posted April 20, 2014 Happy Easter! Here is something I whipped up this weekend from an idea I had, to use the drive-train to power propellers. A.L.T. mkI is an amphibious Lego Technic vehicle and as its name suggests it goes on land and water. Unfortunately is performance wasn't as good as I had hoped. Enjoy, and Happy holidays! Quote
Zerobricks Posted April 20, 2014 Posted April 20, 2014 Not too bad, but were the motors under water? You should try with power puller wheels, those are really full of air :) Quote
Doc_Brown Posted April 20, 2014 Author Posted April 20, 2014 Not too bad, but were the motors under water? You should try with power puller wheels, those are really full of air :) Cheers, narr the motors where close but not under. Power pullers are next for sure! Already tested them, and even tho they weigh 180grams they can take an additional 250grmas of weight before submerged! that's a Kg of body weight motors and battery box, so pretty good really for 4 wheels. Quote
piterx Posted April 20, 2014 Posted April 20, 2014 ahah you do love amphibious models don't you? i like the look it has! yeah maybe performances could be better but it's cool and afterall it works fine eheh waiting for the MK II with PP wheels Quote
JM1971 Posted April 20, 2014 Posted April 20, 2014 Just needs a slope into the water and it can get in and out of the water easily, the closer the fan tip are to cowling the more performance in the water there should be though that may make little difference. Did you watch the banana splits when you was a kid, because I always wanted those 6x6 they drove? Would make a great add on to your rock crawler course having a lake in the middle, it would draw people in from miles around if you do another exhibition in the future. Quote
Doc_Brown Posted April 21, 2014 Author Posted April 21, 2014 Just needs a slope into the water and it can get in and out of the water easily, the closer the fan tip are to cowling the more performance in the water there should be though that may make little difference. Did you watch the banana splits when you was a kid, because I always wanted those 6x6 they drove? Would make a great add on to your rock crawler course having a lake in the middle, it would draw people in from miles around if you do another exhibition in the future. haha, nope I didn't watch them, but their cars seem cool. Actually we have another expo coming up in June, so need to start planning for that. I would deff like to do a water attraction! Also hoping to have a 8x8 rolligon done by then too, just not sure how it will turn being split in the middle and not collapse in the water. Wish I could find better pics Nice Moc is the airtank just cosmetic? um a bit, but mostly I knew it was going to dive into the water so it does help with bouncy a lil bit. 1 air tank can only displace about 30grams of weight, so totally not worth buying say 6 or so and hoping for an awesome craft, would cost way too much. Thanks for the great feed back guys, I've been thinking that I could add panels to the underside in attempt to make less drag underwater, I think this would improve the speed in water a bit. Quote
KirTech LAB Posted April 21, 2014 Posted April 21, 2014 Cool Thing!!! And maybe you can substitute BB for LiPO ? accumulator is much more lighter! Quote
Racerboy Posted April 21, 2014 Posted April 21, 2014 Very cool! If you are interested in making it turn better, consider raising the 4 corner wheels by half a module somehow. The only way that I can see in your MOC to do this would be to have the four corner frames with the gears in them be on a pivot on one end such that the wheels are raised up (lowering the center wheel). This would also require using U-Joints to connect the gearboxes as the axels would need to flex slightly upward from the center boxes. This way only 4 wheels would be contacting the ground at a time depending on weight distribution, center of gravity, and the direction it is going in possibly (if the weight is distributed properly). Just an idea to maybe prototype with. Nice work. Quote
Lakop Posted April 21, 2014 Posted April 21, 2014 Great idea! It floats and moves in the water, i'm sure you could build a mechanism to keep the rotors up and out of the way until it goes in water, and also make the rotors go deeper into the water. Maybe make the rotors bigger. I look forward to seeing it's progress, that's a good start. H Quote
JM1971 Posted April 21, 2014 Posted April 21, 2014 The wheels do stay above the water a fair bit so paddles could be used on the inside and or outside of the wheels, also V shaped tread by glueing strips of rubber onto a old tyre but thats a bit crude, maybe worm gears going the entire length would work, pressurise the tank for more buoyancy and it could also be used to fire a secret weapon. Quote
Doc_Brown Posted April 22, 2014 Author Posted April 22, 2014 Some great ideas guys! Thanks a lot. There is some great opportunity here to develop, and a mech to lift the props sounds awesome! I have no idea how to achieve such a thing tho, haha. Does anyone know if pressurizing a air-tank does increase its buoyancy??? The 98.4mm wheels are more water tight with a rubber-bands in them than the 81mm ones. So the next version maybe larger scale, but I just love those blue rims! haha Quote
Hrafn Posted April 22, 2014 Posted April 22, 2014 Does anyone know if pressurizing a air-tank does increase its buoyancy??? No, it doesn't. Buoyancy is a function of density: the mass of the tank, plus the mass of the air in it, divided by the tank's volume, should be a lower density than water for it to float. The only way to make the tank more buoyant would be to suck air out of it and create a partial (or complete) vacuum inside, but the effect would be small and the tank would likely get destroyed by atmospheric pressure if you had a vacuum inside. Quote
Racerboy Posted April 22, 2014 Posted April 22, 2014 I believe that increasing pressure in a tank will make the tank heavier, and any further increase in pressure will cause the tank to sink. It would be more effective to somehow introduce a vacuum into the tank. I'm not sure if it will do much, however. Feel free to correct me if I am wrong anyone. Oops, didn't see your post Hrafn, apologies. (anyone know why I can't edit my post?) Oh, I didn't know I can build upon my old post. Sorry Quote
Doc_Brown Posted April 22, 2014 Author Posted April 22, 2014 (edited) No, it doesn't. Buoyancy is a function of density: the mass of the tank, plus the mass of the air in it, divided by the tank's volume, should be a lower density than water for it to float. The only way to make the tank more buoyant would be to suck air out of it and create a partial (or complete) vacuum inside, but the effect would be small and the tank would likely get destroyed by atmospheric pressure if you had a vacuum inside. Ahh good to know! Cheers, no chance of making a submarine then, ahha. I believe that is correct, and makes sense, adding more air pressurized will make it sink more. What if you could fill the tank with really really hot air, and then in room temp or even in water it would contract creating more of a vacuum no? I'm just guessing. Also just had the idea to use the air tank on a lever, when in the water the airtank would push the lever up and that could be used to push the props into the water deeper? what do you think guys? :) Edited April 22, 2014 by Doc_Brown Quote
JM1971 Posted April 22, 2014 Posted April 22, 2014 Doc Brown would have no problem building this. Quote
Doc_Brown Posted April 22, 2014 Author Posted April 22, 2014 LOL Your nuts man, I love it :-P hahahah, cheers! Very nice. Love your choice of colours. Thank you! I liked it too. Doc Brown would have no problem building this. Wow thanks for the vote of confidence, but I have never even heard of that! Crazy, wouldn't it kill the fishes, or at least ruin their sense of direction? LOL Quote
JM1971 Posted April 22, 2014 Posted April 22, 2014 Proberbly wouldent do them any good lol and its just something I seen in the hunt for red october, I just noticed the 6 big 36t gears could help it along if the waterline was at the center of them all. Quote
skriblez Posted April 23, 2014 Posted April 23, 2014 The water almost hit the electric parts! Madness! Great work, a fun and nice moc as usual from you :) Quote
Rockbrick Posted April 24, 2014 Posted April 24, 2014 I know the tyres provide the buoyancy - but surely after a while water will seep in and it may sink (but probably after some hours) you would have to glue or grease the tryres on the rim to stop air getting out and water getting in Quote
Doc_Brown Posted April 25, 2014 Author Posted April 25, 2014 I know the tyres provide the buoyancy - but surely after a while water will seep in and it may sink (but probably after some hours) you would have to glue or grease the tryres on the rim to stop air getting out and water getting in Yes this is true, how long you have depends on the rim. for example, the blue rim above doesnt have a lil hole in it so is good in that matter but the tires don't stay on too well. PP rims seem to be the best I have used so far, but are very heavy. Crawler and unimog rims have a little hole and need tape put over them. And when I made the rolligon I used 4 rubber bands on each wheel inside the little groves. I tested this over night in the bath and only a few drops of water got inside. My next test will be crawler tires on PP rims. I'm hoping they will provide the best results Quote
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