Might do bridges this year. How would you do the math on how much each piece could theoretically hold? Also, thanks for the video because it answered my other questions :)
It's towers again this year, but with different (more difficult) rules. Most of the material optimization like you are talking about is done experimentally. It's not too hard to zone in on the correct range of densities to use for each major component but it does require a lot of building and recording video of your failures. Good luck this season!!
Hello! Thank you so much for the video! I was wondering what the top length of this tower would be. With my calculations based off of your drawings, I got 2.5x2.5cm for the top and 21.5x21.5cm for the bottom. Are these measurements correct? I fear the top is too small and may cause the weight to not be distributed correctly.
Hi! The bottom dimension is 21.5x21.5 cm, but the top is the same as the non-bonus at 4x4cm. You can download the actual stl jig files I used from the links in the Intro video if you'd like to see the parts in detail: ua-cam.com/video/ECcz3T6fzPg/v-deo.html
Hi, I just wanted to say that I love and appreciate all of your videos! You do a great job making them! I want your opinion on the tower design with the giant frustum base and a small rectangular prism sticking up from it. I've seen many designs that do that online, but haven't seen you mention it. Are those designs not as effective as the 1 structure tower designs or simply not competitive enough? Thanks!
Hi Jeremy, thanks for the kind words, I really appreciate it! The reason you see a lot of those type designs online is because in the second year of towers, they usually change the rules which make that design a requirement. That was certainly the case in 2018 and I would expect they do something like that again next year too. That type of design is more complicated to build and not as strong as the simple one-piece design, so I wouldn't recommend that for this year. Good luck this season!
Oh no! My students keep getting their tower glued to the jig and then it gets destroyed when trying to remove it when complete. Besides just practicing better precision and using less glue, do you have any tips to prevent gluing the balsa to the plastic?
Hi! I do have a couple recommendations. First, if you haven't already, made sure your students are building the tower with the jig on its side, that really helps with keeping the glue from not getting in to the notches. See the pics of some of my newer videos for more details. If the tower does get stuck, and it sometimes does even with my builds, DON'T try and pull it off by raising it up. Find a small block, I 3d printed one that was 3cm x 3cm x 5mm and temporarily tape this to the top of the jig. Then carefully turn the entire jig upside down on a flat, hard surface. Then press firmly on the bottom of just 2 (or all 4 if you have 2 people) legs at a time and the tower should pop free. I've been thinking about making a video on this process. If all that fails, take some thin strips of wax paper and tape them into the leg groove before the next build. That will definitely work but it's the most time consuming and shouldn't be necessary. Good luck!!
Is the whole length of the leg under an equal amount of stress? Is either the top or the bottom of the tower holding the majority of the load, or is it distributed evenly? If the distribution isn't equal, would it be worth it to change the distance between each layer of cross members so that the places under more stress has a smaller gap between cross member layers, and the places under less stress has a larger gap between cross member layers?
For all my build videos, you can freeze frame on my notebook page where I show exactly the dimensions and mass of each piece. From that you should be able to easily compute the weight for any size sticks
Hi, i had my first go at building a tower, but I accidentally super glued it to my jig and I couldn't get it off. I was super careful with gluing to try and prevent this but I guess it was kind of inevitable. Would you be against it if I were to wrap my jig in something like saran wrap so the tower would only be stuck to the saran wrap if this were to happen again? thanks
Hi! Yeah, that can happen unfortunately. First, if you are going to try and directly prevent it, I would use wax paper instead of saran wrap. The best tip is to build the tower with the jig flat on the table one side at a time. This really helps you control the amount of glue and limit the dripping into the grooves. If it does get stuck, what I have found that works well is to find a small block, I 3d printed one 30x30x5mm. Temporarily tape it to the top of your jig. Then turn the entire thing upside down and put it on a hard, flat table. Then carefully but firmly press on at least two legs at a time from the bottom. With any luck, your tower will pop off the jig without any damage. This technique worked well for me when this happens. Good luck!!
This question is more for general knowledge than building advice, but how do such lightweight pieces of balsa support such heavy weight? I understand the sheer amount of cross-members and the even distribution of weight across all of them allows for a high buckling strength, but in the past, the pieces I've handled that are this light are so soft they dent to the touch, so how is it possible?
The main reason is that balsa is an amazing material! It can be even stronger than steel by weight. While I am using the light side of the "light" range of 6-10 lbs/ft^3, the really squishy stuff you are talking about is even lighter than that. I wouldn't recommend using that range as the strength to weight ratio goes down quickly. Check out this video when you get a chance: ua-cam.com/video/mzMFhd4SqP8/v-deo.htmlsi=izWDuw3luNPbFkCz
Is it wise to even consider using 1/32 by 1/32(or 1/16) bass pieces for the cross-members, or is it too heavy that it brings down efficiency by a considerable amount? The cross-members this year are incredibly light and compared to bridges, the balsa pieces look like they weigh nothing. If I use any random piece of low-weight, low-density wood (within the weight range), it could severely hinder the tower, so I wanted to know what specific density range you order from Specialized Balsa to get the cross-members.
Even 1/32 x 1/32 bass is too heavy for this application to be competitive. Getting the right material can be a challenge for sure, and even when you get the proper sheets, you'll have to cut a bunch of strips and weigh them individually to make sure they are OK. Definitely document in your journal the weight of each cross member layer, not just for documentation purposes, but to make sure you don't put in a piece that is bad (too heavy or too light). I would start with the "light" range of balsa 6-10 lbs/cu^3 from Specialized Balsa. You might enjoy this video I made on density vs efficiency that goes over a bunch of this in more detail: ua-cam.com/video/mzMFhd4SqP8/v-deo.html
Since the sides form an x and one line of the x has to go over the other line of the x, do you make it so the one line of the x is always the one that goes over the other line of the x on every single cross section or do you alternate it?
Yes, for sure! Check out the video I made on balsa to see the best density range to choose from for these builds: ua-cam.com/video/mzMFhd4SqP8/v-deo.html
You can download all the STL files from the description of the Intro video: ua-cam.com/video/ECcz3T6fzPg/v-deo.html You'll have to print them yourself or send them to an online service to get printed. You can see the size of the material I used if you examine the notebook pages I show in all of my videos. In general, the legs are 1/8 x 1/8 and the cross members are typically anything from 1/16x1/20 to 1/20x1/32
@@Trygod The Div C jigs are just the Div B jigs scaled 120% in the Z direction only. I also have included a zip with all of those in case you don't want to scale it yourself in the slicer program
I built a bonus tower that held over 15kg, but tower is 14g. I built another one about 9.8g. But I didn’t test it. I want to bring it to the competition without testing it. Will the tower be tested several times?
@@gabrieldeng3990 It's up to you if you want to pre-test your tower before the competition. If you are building to the bonus rules, I'd probably test to 15kg (only) to make sure it can hold the entire weight
Alr so here are my own findings, I used materials from last year, so it wasn't completely optimized yet, nor will the next one which I am building rn, but I have one at 1200 efficiency and the next one is estimated to be somewhere around 1600 efficiency (both with log bonus and build bonus) We have done 10 layers for the first one, but we added a thick strip across the bottom on all 4 sides, I believe 1/4 by 1/16 inch, and during recording the tower didn't even move, so odds are it probably could have held another couple kgs, this next one we are lowering the amount of layers to 6, keeping the bottom strip, and possibly adding a thin strip between cross pairs 3 and 4 for extra stability. These two were build on 1/8 by 1/4 legs which increased the weight of the legs by almost 2 times, with the leg weight being around 7.3, on the tower after this one, we are going for 1/8 by 1/8 medium density legs, and using 1/16 by 1/16 for ten layers medium density for 5, and light for the top five, along with the strip at the bottom being medium 1/16^2 and a strip at the very top being light 1/16^2 for a VERY rough estimated score of around 2500
Thanks for sharing! Please let me know if you get close to a 6-6.25g tower that achieves the bonus. That is what it will take to even consider bringing one to competition compared to a non-bonus tower due to the extra risk involved (IMHO). Good luck!!
All 3d printers are slightly different, so your results may be a bit different, but at 10% infill, the Div C jigs took just over 48 hrs for all 3 pieces for the non-bonus version and around 73 hrs for the bonus version (the Div B versions were about 20% less time)
Might do bridges this year. How would you do the math on how much each piece could theoretically hold? Also, thanks for the video because it answered my other questions :)
It's towers again this year, but with different (more difficult) rules. Most of the material optimization like you are talking about is done experimentally. It's not too hard to zone in on the correct range of densities to use for each major component but it does require a lot of building and recording video of your failures. Good luck this season!!
Hello! Thank you so much for the video! I was wondering what the top length of this tower would be. With my calculations based off of your drawings, I got 2.5x2.5cm for the top and 21.5x21.5cm for the bottom. Are these measurements correct? I fear the top is too small and may cause the weight to not be distributed correctly.
Hi! The bottom dimension is 21.5x21.5 cm, but the top is the same as the non-bonus at 4x4cm. You can download the actual stl jig files I used from the links in the Intro video if you'd like to see the parts in detail: ua-cam.com/video/ECcz3T6fzPg/v-deo.html
Hi, I just wanted to say that I love and appreciate all of your videos! You do a great job making them!
I want your opinion on the tower design with the giant frustum base and a small rectangular prism sticking up from it. I've seen many designs that do that online, but haven't seen you mention it. Are those designs not as effective as the 1 structure tower designs or simply not competitive enough? Thanks!
Hi Jeremy, thanks for the kind words, I really appreciate it! The reason you see a lot of those type designs online is because in the second year of towers, they usually change the rules which make that design a requirement. That was certainly the case in 2018 and I would expect they do something like that again next year too. That type of design is more complicated to build and not as strong as the simple one-piece design, so I wouldn't recommend that for this year. Good luck this season!
Oh no! My students keep getting their tower glued to the jig and then it gets destroyed when trying to remove it when complete. Besides just practicing better precision and using less glue, do you have any tips to prevent gluing the balsa to the plastic?
Hi! I do have a couple recommendations. First, if you haven't already, made sure your students are building the tower with the jig on its side, that really helps with keeping the glue from not getting in to the notches. See the pics of some of my newer videos for more details. If the tower does get stuck, and it sometimes does even with my builds, DON'T try and pull it off by raising it up. Find a small block, I 3d printed one that was 3cm x 3cm x 5mm and temporarily tape this to the top of the jig. Then carefully turn the entire jig upside down on a flat, hard surface. Then press firmly on the bottom of just 2 (or all 4 if you have 2 people) legs at a time and the tower should pop free. I've been thinking about making a video on this process. If all that fails, take some thin strips of wax paper and tape them into the leg groove before the next build. That will definitely work but it's the most time consuming and shouldn't be necessary. Good luck!!
Is the whole length of the leg under an equal amount of stress? Is either the top or the bottom of the tower holding the majority of the load, or is it distributed evenly? If the distribution isn't equal, would it be worth it to change the distance between each layer of cross members so that the places under more stress has a smaller gap between cross member layers, and the places under less stress has a larger gap between cross member layers?
The loading of the legs are under even loading throughout the entire length so it wouldn't be a good idea to have different spacing from top to bottom
What is your weight per 36 cm stick (in grams) for the 1/8 x 1/8 wood and the 1/16 by 1/16 wood?
For all my build videos, you can freeze frame on my notebook page where I show exactly the dimensions and mass of each piece. From that you should be able to easily compute the weight for any size sticks
Hi, i had my first go at building a tower, but I accidentally super glued it to my jig and I couldn't get it off. I was super careful with gluing to try and prevent this but I guess it was kind of inevitable. Would you be against it if I were to wrap my jig in something like saran wrap so the tower would only be stuck to the saran wrap if this were to happen again? thanks
Hi! Yeah, that can happen unfortunately. First, if you are going to try and directly prevent it, I would use wax paper instead of saran wrap. The best tip is to build the tower with the jig flat on the table one side at a time. This really helps you control the amount of glue and limit the dripping into the grooves. If it does get stuck, what I have found that works well is to find a small block, I 3d printed one 30x30x5mm. Temporarily tape it to the top of your jig. Then turn the entire thing upside down and put it on a hard, flat table. Then carefully but firmly press on at least two legs at a time from the bottom. With any luck, your tower will pop off the jig without any damage. This technique worked well for me when this happens. Good luck!!
This question is more for general knowledge than building advice, but how do such lightweight pieces of balsa support such heavy weight? I understand the sheer amount of cross-members and the even distribution of weight across all of them allows for a high buckling strength, but in the past, the pieces I've handled that are this light are so soft they dent to the touch, so how is it possible?
The main reason is that balsa is an amazing material! It can be even stronger than steel by weight. While I am using the light side of the "light" range of 6-10 lbs/ft^3, the really squishy stuff you are talking about is even lighter than that. I wouldn't recommend using that range as the strength to weight ratio goes down quickly. Check out this video when you get a chance: ua-cam.com/video/mzMFhd4SqP8/v-deo.htmlsi=izWDuw3luNPbFkCz
Hi, what is the bottom width of the bonus tower? I see the non-bonus width is around 15cm wide at the bottom
Hi! The base of my bonus tower jig is 215x215mm. The non-bonus one is 152x152mm.
I didn't understand did you mean 21.5 cm? @@balsaengineering6686
Is it wise to even consider using 1/32 by 1/32(or 1/16) bass pieces for the cross-members, or is it too heavy that it brings down efficiency by a considerable amount? The cross-members this year are incredibly light and compared to bridges, the balsa pieces look like they weigh nothing. If I use any random piece of low-weight, low-density wood (within the weight range), it could severely hinder the tower, so I wanted to know what specific density range you order from Specialized Balsa to get the cross-members.
Even 1/32 x 1/32 bass is too heavy for this application to be competitive. Getting the right material can be a challenge for sure, and even when you get the proper sheets, you'll have to cut a bunch of strips and weigh them individually to make sure they are OK. Definitely document in your journal the weight of each cross member layer, not just for documentation purposes, but to make sure you don't put in a piece that is bad (too heavy or too light). I would start with the "light" range of balsa 6-10 lbs/cu^3 from Specialized Balsa. You might enjoy this video I made on density vs efficiency that goes over a bunch of this in more detail: ua-cam.com/video/mzMFhd4SqP8/v-deo.html
Since the sides form an x and one line of the x has to go over the other line of the x, do you make it so the one line of the x is always the one that goes over the other line of the x on every single cross section or do you alternate it?
I try to alternate them to offset any effect that might induce
I was wondering why you did not add 5000 grams in the mass held. Is this not a bonus point tower?
You only get to add the extra 5000g if your tower holds the entire 15kg
Is balsa the best type of wood to use?
Yes, for sure! Check out the video I made on balsa to see the best density range to choose from for these builds: ua-cam.com/video/mzMFhd4SqP8/v-deo.html
Where can I buy the jigs? Also what size wood did you use?
You can download all the STL files from the description of the Intro video: ua-cam.com/video/ECcz3T6fzPg/v-deo.html You'll have to print them yourself or send them to an online service to get printed. You can see the size of the material I used if you examine the notebook pages I show in all of my videos. In general, the legs are 1/8 x 1/8 and the cross members are typically anything from 1/16x1/20 to 1/20x1/32
@@balsaengineering6686but that video only contains the div b jigs right? How about the jigs for div c
@@Trygod The Div C jigs are just the Div B jigs scaled 120% in the Z direction only. I also have included a zip with all of those in case you don't want to scale it yourself in the slicer program
I built a bonus tower that held over 15kg, but tower is 14g. I built another one about 9.8g. But I didn’t test it. I want to bring it to the competition without testing it. Will the tower be tested several times?
During competition, the tower is only tested once. Good luck!
I mean, do I need take a test before competition? Thanks
@@gabrieldeng3990 It's up to you if you want to pre-test your tower before the competition. If you are building to the bonus rules, I'd probably test to 15kg (only) to make sure it can hold the entire weight
Where do you get your material from? I’ve only found 1/16 by 3/16?
I like to buy balsa sheets from Specialized Balsa: specializedbalsa.com/products/balsa_sheets.php and then cut all my own strips from that
where can i get the lowest density wood?
I like to buy all my balsa sheets from Specialized Balsa where you can specify a density range or even very specific if you are willing to pay extra.
@@balsaengineering6686 How long would it take for it to aarive?
@@vihaankinra615 It depends, but in my experience, it usually takes about 1-2 weeks
@@balsaengineering6686so you bought balsa sheets not the sticks?
Alr so here are my own findings, I used materials from last year, so it wasn't completely optimized yet, nor will the next one which I am building rn, but I have one at 1200 efficiency and the next one is estimated to be somewhere around 1600 efficiency (both with log bonus and build bonus) We have done 10 layers for the first one, but we added a thick strip across the bottom on all 4 sides, I believe 1/4 by 1/16 inch, and during recording the tower didn't even move, so odds are it probably could have held another couple kgs, this next one we are lowering the amount of layers to 6, keeping the bottom strip, and possibly adding a thin strip between cross pairs 3 and 4 for extra stability. These two were build on 1/8 by 1/4 legs which increased the weight of the legs by almost 2 times, with the leg weight being around 7.3, on the tower after this one, we are going for 1/8 by 1/8 medium density legs, and using 1/16 by 1/16 for ten layers medium density for 5, and light for the top five, along with the strip at the bottom being medium 1/16^2 and a strip at the very top being light 1/16^2 for a VERY rough estimated score of around 2500
Thanks for sharing! Please let me know if you get close to a 6-6.25g tower that achieves the bonus. That is what it will take to even consider bringing one to competition compared to a non-bonus tower due to the extra risk involved (IMHO). Good luck!!
Ty!
How long do the jigs take to print?
All 3d printers are slightly different, so your results may be a bit different, but at 10% infill, the Div C jigs took just over 48 hrs for all 3 pieces for the non-bonus version and around 73 hrs for the bonus version (the Div B versions were about 20% less time)
What glue do you use?
I like to use 50 cps CA glue. You can check out my entire video on glue and gluing techniques if you want: ua-cam.com/video/55lb2KzSiwg/v-deo.html
@@balsaengineering6686Thanks! Also where do you buy your balsa?
@@sungjin... Thanks! I like to buy my balsa sheets from Specialized Balsa: specializedbalsa.com/products/balsa_sheets.php