TechnicBrickPower Posted January 29, 2020 Posted January 29, 2020 Hi Everyone, I have made a video about creating a 7:1 gear ratio mechanism using just 2:1, 3:1 and 5:1 gears. No 28 teeth gears used. Youtube subscriptions appreciated! Kind Regards and keep building, Rob Quote
TechnicBrickPower Posted January 31, 2020 Author Posted January 31, 2020 Hi Just an update...someone on reddit posted that you can create an exact 7:1 using a differential with 1:5, and 1:9 input to create a 1:7. Quote
TeamThrifty Posted January 31, 2020 Posted January 31, 2020 Problem solving is a key part of technic.. quite often there are posts asking for help solving things before the poster has really got stuck into it. Not everyone is a problem solver, and people take different things from lego, but for me, sitting and trying, re-trying, iteration after iteration, sometimes for days, is what i love... its like playing chess with lego pieces! Quote
doug72 Posted January 31, 2020 Posted January 31, 2020 1 hour ago, TeamThrifty said: Problem solving is a key part of technic.. quite often there are posts asking for help solving things before the poster has really got stuck into it. Not everyone is a problem solver, and people take different things from lego, but for me, sitting and trying, re-trying, iteration after iteration, sometimes for days, is what i love... its like playing chess with lego pieces! Agree, thats why I enjoy GBC with its complex gearing and trying to come up with workable solutions. My current build has gone through several solutions - workable but too slow so still under developement. Having said that can't se the point of super cars having 4 & 8 speed gear boxes if model is only for dis[play ! Quote
TeamThrifty Posted January 31, 2020 Posted January 31, 2020 1 minute ago, Doug72 said: Having said that can't se the point of super cars having 4 & 8 speed gear boxes if model is only for dis[play Agree completely.. mind you the whole display thing is lost on me, technic has mechanics at its heart, its meant to be used, taken to bits and re-used..! Quote
Wismill Posted January 31, 2020 Posted January 31, 2020 (edited) 2 hours ago, TechnicBrickPower said: Hi Just an update...someone on reddit posted that you can create an exact 7:1 using a differential with 1:5, and 1:9 input to create a 1:7. Here is the comment on reddit. The mechanism was used to built a very interesting Antikythera Mechanism to calculate eclipses of the sun and the moon. Check the corresponding website, it's worth it! Edit: of course there is a dedicated topic on EB. Edited January 31, 2020 by Wismill Quote
Erik Leppen Posted January 31, 2020 Posted January 31, 2020 (edited) Interesting. It's not exact 1/7, as you show, but it's surprisingly close. In fact it's 20/12 * 8/24 * 8/24 * 40/24 * 8/24 * 20/12 * 20/24. This comes down to 5/3 * 1/3 * 1/3 * 5/3 * 1/3 * 5/3 * 5/6 i.e. (5*5*5*5) / (3*3*3*3*3*3*6) i.e. 625/4374 If you compare this to 1/7 by dividing it: (625/4374) / (1/7), then you get (625/4374) * 7 = 4375/4374. Interesting how these two highly-factorable numbers are only 1 apart. (sorry. Once a mathematician, always a mathematician :D ) How did you find these two numbers? By chance, or did you run some numbers beforehand to get it? Also, playing with gears is fun :D Edited January 31, 2020 by Erik Leppen Quote
Jim Posted January 31, 2020 Posted January 31, 2020 On 1/29/2020 at 3:22 AM, TechnicBrickPower said: Hi Everyone, I have made a video about creating a 7:1 gear ratio mechanism using just 2:1, 3:1 and 5:1 gears. No 28 teeth gears used. Youtube subscriptions appreciated! Kind Regards and keep building, Rob Hi, Please be aware that Eurobricks is not a platform to promote your channel. Thanks. Quote
TeamThrifty Posted January 31, 2020 Posted January 31, 2020 1 hour ago, Erik Leppen said: sorry. Once a mathematician, always a mathematician Don't be sorry! I have just enough maths to do my job, but love to see some proper analysis!! Brilliant post. Quote
Pvdb Posted January 31, 2020 Posted January 31, 2020 7 hours ago, Doug72 said: Having said that can't se the point of super cars having 4 & 8 speed gear boxes if model is only for dis[play ! For me one of the most interesting parts of designing a supercar is developing the gearbox. Then comes the different challenge of designing the car that looks good around it. Quote
TeamThrifty Posted January 31, 2020 Posted January 31, 2020 I agree, gearboxes are a fascinating thing to design and build... its just sitting them on a shelf as display-only that confuses me. I want to see them, and use them. Lego is about interaction. Airfix is about display... at least to me Quote
TechnicBrickPower Posted February 2, 2020 Author Posted February 2, 2020 On 2/1/2020 at 4:33 AM, Erik Leppen said: Interesting. It's not exact 1/7, as you show, but it's surprisingly close. In fact it's 20/12 * 8/24 * 8/24 * 40/24 * 8/24 * 20/12 * 20/24. This comes down to 5/3 * 1/3 * 1/3 * 5/3 * 1/3 * 5/3 * 5/6 i.e. (5*5*5*5) / (3*3*3*3*3*3*6) i.e. 625/4374 If you compare this to 1/7 by dividing it: (625/4374) / (1/7), then you get (625/4374) * 7 = 4375/4374. Interesting how these two highly-factorable numbers are only 1 apart. (sorry. Once a mathematician, always a mathematician :D ) How did you find these two numbers? By chance, or did you run some numbers beforehand to get it? Also, playing with gears is fun :D Yes you're right it's out by 1/625 from 7, i.e. 6.9984 = 7 - 1/625. I found this by running a search algorithm and it can find ratios to a high precision, but these need 1000's of gears - so not practical! For example 5 ^ 571 / (3 ^ 571 x 2 ^ 418) = 6.99999683. Quote
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