arshiaIQ Posted May 26, 2016 Posted May 26, 2016 (edited) Ive been looking for a driven axle using knob gears, not cv/u-joints since they are weak Does anybody have any idea? I also found this on moc-pages but nearly all photos and video are dead http://www.moc-pages.com/moc.php/256284 Edited May 26, 2016 by arshiaIQ Quote
Jim Posted May 26, 2016 Posted May 26, 2016 Hi, Welcome to EB! I think this topic can be interesting: http://www.eurobricks.com/forum/index.php?showtopic=92099 Quote
Saberwing40k Posted May 26, 2016 Posted May 26, 2016 Why do you think U joints are weak? unless you are building something really heavy, with no axle reduction, I find u joints to work just fine. Quote
Imanol BB Posted May 27, 2016 Posted May 27, 2016 I think that you could find some ideas here: http://www.eurobricks.com/forum/index.php?showtopic=60459&st=0 Quote
syclone Posted May 27, 2016 Posted May 27, 2016 Do you have any specs? Width,differential or no... Quote
arshiaIQ Posted May 27, 2016 Author Posted May 27, 2016 Why do you think U joints are weak? unless you are building something really heavy, with no axle reduction, I find u joints to work just fine. Actually U-joints break so easily... specially their outer rim is so weak... all U-joints I have are broken in this way, even without any load but only with putting an axle through it after a few times! Do you have any specs? Width,differential or no... Width about 13 or 15... with differential... Actually high ground clearence and small pivot distance from wheels are more important... since im looking for an idea, so i can use it to implant width and diff. later Excuse me... I'm so noob in this community :D Quote
syclone Posted May 27, 2016 Posted May 27, 2016 (edited) Using knob gears you won't get very close to the wheel. By myself never had problems with CV and U-joints.Anyway, I am designing one for you :) Edited May 27, 2016 by LXF Quote
syclone Posted May 27, 2016 Posted May 27, 2016 (edited) I have something for you: LDD Is this what you wanted? You can place an 11l steering rack instead of that contraption Edited May 27, 2016 by LXF Quote
Didumos69 Posted May 27, 2016 Posted May 27, 2016 (edited) I took this as a challenge too (no offence LXF). Something sturdy with the wheel hubs being supported above and beneath the horizontal knob wheel. Hopefully this will help you getting started. It includes Ackermann steering. The gear rack side should be seen as the front side of the module. EDIT: Actually it is the other way around; the gear rack side should be regarded as the back side of the module. See reply number 11. I updated the images and the LXF-file below accordingly. LXF-file here. Edited May 30, 2016 by Didumos69 Quote
syclone Posted May 27, 2016 Posted May 27, 2016 (edited) Masterpiece! Much better than mine!!! Mine is a quick build made as light as possible and nothing under the diff. @arshialQ - you should go with the Didumos69's one , it is much sturdier Edited May 27, 2016 by LXF Quote
Didumos69 Posted May 27, 2016 Posted May 27, 2016 (edited) I took this a s a challenge too (no offence LXF). Something sturdy with the wheel hubs being supported above and beneath the horizontal knob wheel. Hopefully this will help you getting started. It includes Ackermann steering. The gear rack side should be seen as the front side of the module. LXF-file here. Turns out that Ackermann steering is almost negligible. It actually has the opposite effect of what I expected, So you would have to tweak the wheel hub - gear rack connection a little or use the module the other way around, with the gear rack at the back side of the module that is. You can move the gears at the front to the other side of the module, which would make the upper axle the drive axle and the lower axle the steering axle. The operation and sturdiness of the wheel hubs and knob gears should be just fine. Edited May 28, 2016 by Didumos69 Quote
arshiaIQ Posted May 27, 2016 Author Posted May 27, 2016 (edited) I have something for you: LDD Is this what you wanted? You can place an 11l steering rack instead of that contraption Good... but for low weight... Well thanks for your idea ;) Turns out that Ackermann steering is almost negligible. It actually has the opposite effect of what I expected, So you would have to tweak the wheel hub - gear rack connection a little or use the module the other way around, with the gear rack at the back side of the module that is. You can move the gears at the front to the other side of the module, which would make the upper axle the drive axle and the lower axle the steering axle. The operation and sturdiness of the wheel hubs and knob gears should be just fine. I appreciate this design... sturdy and robust with satisfiyng ground clearence Thanks, its what Ive been looking for Using knob gears you won't get very close to the wheel. By myself never had problems with CV and U-joints.Anyway, I am designing one for you :) Well to be honest, I have only one cv-joint pair, the one for 42043 And about 8 new u-joints and 2 old 4-stud long, most of them has some cracks and broken sections which scare me! This is a really bad thing which most of technic connectors and bushes have... making them weak!! Unfortunately there is no bricklink stores for my country and I cant even pay due to lack of international credit cards here... so i should take care of my parts! Lego/MOCing in my country is DEAD! Edited May 28, 2016 by arshiaIQ Quote
Mantarri Posted May 27, 2016 Posted May 27, 2016 Unfortunately there is no bricklink stores for my country and I cant even pay due to lack of international credit cards here... so i should take care of my parts! Lego/MOCing in my country is DEAD! That must really suck, well you better check your local equivalent of craigslist, maybe some In search of ads on some face buy + sell +trade group. Quote
arshiaIQ Posted May 27, 2016 Author Posted May 27, 2016 That must really suck, well you better check your local equivalent of craigslist, maybe some In search of ads on some face buy + sell +trade group. Not such thing... I only can buy sets from some toy shops Here people use lego as decoration (hell dammit!) There is nothing about lego... when i build something my classmates freak out, even with a normal thing Quote
Mantarri Posted May 27, 2016 Posted May 27, 2016 Not such thing... I only can buy sets from some toy shops Here people use lego as decoration (hell dammit!) There is nothing about lego... when i build something my classmates freak out, even with a normal thing That's too bad. :( I'm budget limited, but have access to a whole boatload of stuff. Quote
arshiaIQ Posted May 27, 2016 Author Posted May 27, 2016 That's too bad. :( I'm budget limited, but have access to a whole boatload of stuff. Well, save up! Quote
Didumos69 Posted May 27, 2016 Posted May 27, 2016 (edited) I appreciate this design... sturdy and robust with satisfiyng ground clearence Thanks, its what Ive been looking for :thumbup: You're welcome! I just build my design and it operates as expected. I don't have the knob gears so I used the 12 tooth bevel gears instead, but there is space enough for the knob gears, also in turns. In my build the upper input axle is for drive and the lower input axle is for steering. I used the 5.5L axle with end-stop as vertical steering axle and as wheel axle to prevent these axles from falling out. Edited May 29, 2016 by Didumos69 Quote
arshiaIQ Posted May 28, 2016 Author Posted May 28, 2016 (edited) :thumbup: You're welcome! I just build my design and it operates as expected. I don't have the knob gears so I used the 12 tooth bevel gears instead, but there is space enough for the knob gears, also in turns. In this build the upper input axle is for drive and the lower input axle is for steering. Btw, you should know that I used the 5.5L axle with end-stop as vertical steering axle and as wheel axle to prevent these axles from getting displaced. Yea such a robust design... i like the ground clearence it makes using unimog wheels... Would you explain how does ackerman steering works here? According to my findings there should be a relation between the front and rear axles and the pivot point Edited May 28, 2016 by arshiaIQ Quote
Didumos69 Posted May 28, 2016 Posted May 28, 2016 (edited) Yea such a robust design... i like the ground clearence it makes using unimog wheels... Would you explain how does ackerman steering works here? According to my findings there should be a relation between the front and rear axles and the pivot point Unimog wheels fit perfectly. Indeed for Ackermann steering there is a relation between the wheel base and the pivot offset; a longer wheel base asks for a SMALLER pivot offset. However this relation assumes a straight connection between the left and right pivot points. In my setup the gear rack moves along a straight line and two tie rods link the gear rack to the pivot points. This also affects the steering angle difference between left and right. In my design the latter effect is stronger than the pivot offset effect and works in the opposite direction. That's why the overall Ackermann effect is quite small, although it still suprised me after building these axles. You can tweak the Ackermann effect by changing the pivot points or the points where the tie rods connect to the gear rack, but the options are limited in this compact setup with 6 knob gears eating up a lot of space One off-topic hint: Better remove video's and images in quotes. Moderators don't like that Edited May 28, 2016 by Didumos69 Quote
arshiaIQ Posted May 28, 2016 Author Posted May 28, 2016 Unimog wheels fit perfectly. Indeed for Ackermann steering there is a relation between the wheel base and the pivot offset; a longer wheel base asks for a SMALLER pivot offset. However this relation assumes a straight connection between the left and right pivot points. In my setup the gear rack moves along a straight line and two tie rods link the gear rack to the pivot points. This also affects the steering angle difference between left and right. In my design the latter effect is stronger than the pivot offset effect and works in the opposite direction. That's why the overall Ackermann effect is quite small, although it still suprised me after building these axles. You can tweak the Ackermann effect by changing the pivot points or the points where the tie rods connect to the gear rack, but the options are limited in this compact setup with 6 knob gears eating up a lot of space One off-topic hint: Better remove video's and images in quotes. Moderators don't like that Got it... I realized that I can have a great steering angle by tweaking the rack a bit, much higher than what achievable angle using cv/u-joints There's a question, are cv-joints' movement also sine-waved like u-joints or not? Btw i edited my posts also, thanks for all your attention ;) Quote
Didumos69 Posted May 28, 2016 Posted May 28, 2016 (edited) Got it... I realized that I can have a great steering angle by tweaking the rack a bit, much higher than what achievable angle using cv/u-joints There's a question, are cv-joints' movement also sine-waved like u-joints or not? Btw i edited my posts also, thanks for all your attention ;) CV-joints are constant velocity joints, so they don't suffer from the sine-wave. The knob gear arrangement also boils down to a constant-velocity joint. Standard CV-joints indeed allow for a small steering angle only. U-joints are not so bad in that regard, but they suffer from a gradually increasing sine wave as the steering angle increases. Btw, I have been able to extend my design with an extra slider attached to the gear rack. It adds more stability to the gear rack. I updated the video and the LXF-file accordingly. Edited May 28, 2016 by Didumos69 Quote
Sylvian Posted May 28, 2016 Posted May 28, 2016 Love this concept as an alternative for a portal axle,.. gotta give this my own attempt,. Very nice,! Quote
Didumos69 Posted May 29, 2016 Posted May 29, 2016 (edited) I realized that I can have a great steering angle by tweaking the rack a bit, much higher than what achievable angle using cv/u-joints I'm affraid I missed this sentence when I first read your last post. I'm a little curious about how you tweaked the gear rack. Would also be great to see some pictures of what you're actually building. Anyway, good luck with your build! Edited May 29, 2016 by Didumos69 Quote
OriolesFan957 Posted May 30, 2016 Posted May 30, 2016 Hi, I am new here and I was wondering if I could get some tips. You see I am trying to build a technic power functions tracked vehicle. Just need some pointers. I have already remodeled it 3 times, and have not even added the motor or battery box in yet. I am also new to adding in power functions to vehicles. Also, I am sorry for interrupting your topic. Quote
Didumos69 Posted May 30, 2016 Posted May 30, 2016 (edited) Hi, I am new here and I was wondering if I could get some tips. You see I am trying to build a technic power functions tracked vehicle. Just need some pointers. I have already remodeled it 3 times, and have not even added the motor or battery box in yet. I am also new to adding in power functions to vehicles. Also, I am sorry for interrupting your topic. I'd scan this forum for examples or search rebrickable.com for MOCs with PFs. There are a lot of examples with free instructions. Searching this forum is limited to avoid overload, You can use Google and also type 'eurobricks'. And if you still don't find what your looking for, then simply post a new topic to the technic forum with your question. Edited May 30, 2016 by Didumos69 Quote
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