Compact Sequential Stepper

[Boxerlego]

About unwanted rotation of the knob gear: The integrated limiter serves as a first line of defense; it makes sure the knob gear axle prefers to sit in perfect 90 degree orientations. It has proven useful in the 42056 Porsche to avoid double engaged gears. As for the exact locking behaviour of the complete stepper I think Attika has to answer himself. I have a slightly different implementation that is intended to slip through the stepper part.

Ok that makes sense the stepper mechanism is designed to slip so it can retract back to the starting position. Now since its designed to slip in some sense to function my question here is how well will the stepper mechanism natural ability just to hold the knob gear in place. I like how the stepper mechanism functions as a 4 position turn ratchet. I understand what you mean by the integrated limiter and what it is but with out it how well does this work, If I wanted to "backdrive" the stepper mechanism with the knob gear shaft?

Hi, as I wrote a couple of lines above if you use it a non motorised model there isn't enough countertorque to get it out from the gear. If you motorise it, using either servo motor or pf m motor with return to center mechanism, both holds the lever strong enough to prevent unwanted gearchange. I hope if you watch over the video concidering this explanation you will recognise the effect I wrote and the physics vehind it. I'm abroad right now therefore unable to post a video that highlights this. As you wrote this is a concept only so theres plenty of room to develop it to match certain requirements. Don't hesitate build it and experiment on it. You are free to use and modify it to your own taste. Thanks for poping in.

Ok, so the motor here is what provides the "resistance" to hold the knob gear in place. That makes sense. I will certainly try my hand at building one and do my own developing with it I got some unique ideas I want to test out.

Edited August 23, 2016 by Boxerlego

[Didumos69]

Ok that makes sense the stepper mechanism is designed to slip so it can retract back to the starting position. Now since its designed to slip in some sense to function my question here is how well will the stepper mechanism natural ability just to hold the knob gear in place. I like how the stepper mechanism functions as a 4 position turn ratchet. I understand what you mean by the integrated limiter and what it is but with out it how well does this work, If I wanted to "backdrive" the stepper mechanism with the knob gear shaft?

At the end of

from a few posts above you see what happens when I drive the knob gear axle by hand. But beware that I have a slightly different implementation compared to Attika. Edited August 23, 2016 by Didumos69

[Didumos69]

Something similar, also uses a limiter. It uses a 3L lever : wink:.

Btw, I tried using the limiter open ended like this, but it will slowly slide the #2 connector off the axle. Still a useful concept though.

Edited August 25, 2016 by Didumos69

[Boxerlego]

Ok I recently built this and it works good. Found out that it can work backwards and that it does need the limiter to function properly other wise the stepper mechanism don't work as well. I made some miner adjustments to the way the rubber bands were setup so instead of dismantling the entire model to get to that one rubber band that is around the shaft, two small rubber bands can now be placed easily on each side for the same effect with out the trouble. Now I keep adjusting the tension on the rubber bands until the device is able to naturally snap back to starting position after one complete function. I found out that for a good working stepper function that the rubber band tension on the stepper mechanism should not exceed the rubber band tension on the limiter device and in fact the whole function of the device really depends on how well the rubber bands on the limiter device can hold, secure and release the shaft. If the rubber band on the stepper mechanism is stronger then the limiter device the stepper mechanism ability to slip over the knob gear does not function as desired.

[Didumos69]

Ok I recently built this and it works good. Found out that it can work backwards and that it does need the limiter to function properly other wise the stepper mechanism don't work as well. I made some miner adjustments to the way the rubber bands were setup so instead of dismantling the entire model to get to that one rubber band that is around the shaft, two small rubber bands can now be placed easily on each side for the same effect with out the trouble. Now I keep adjusting the tension on the rubber bands until the device is able to naturally snap back to starting position after one complete function. I found out that for a good working stepper function that the rubber band tension on the stepper mechanism should not exceed the rubber band tension on the limiter device and in fact the whole function of the device really depends on how well the rubber bands on the limiter device can hold, secure and release the shaft. If the rubber band on the stepper mechanism is stronger then the limiter device the stepper mechanism ability to slip over the knob gear does not function as desired.

I had the same experience. I would even argue that the tension on the stepper silicon band should be substantially less than the tension on the limiter silicon band.

I'm currently trying to figure out how I can use the same mechanism to redesign the PDK-unit - this thing where you've already won your spurs - in my ultimately playable version of the Porsche. This also explains why I see the slipping as advantage, as that version also features HoG shifting.

Looking forward how will you implement it in the porsche

Works out very fine. The two pushers operate separtely and are moved back into straight position without using rubbers or silicon bands. The paddle shifters operate way more smooth than in the original model :

Edited August 26, 2016 by Didumos69

[Attika]

Works out very fine. The two pushers operate separtely and are moved back into straight position without using rubbers or silicon bands. The paddle shifters operate way more smooth than in the original model

Sorry, I had an offline weekend. Nice application. I'm glad to contribute in your "big project".

Edited August 29, 2016 by Attika

[Charlieca00907]

I very much like your stepper mechanism. After building a few from varios different youtube videos, yours was absolutely genius in its simplicity and reliability. Currently, I am building my first supercar after getting inspired by the GT3, Koenigsegg One MOC and Aventador Pirelli Edition MOC that I have recently built. I have found that sheepo's modular system seems to be a good starting point for the chassis. At the moment I have managed to get a working remote control chassis using the modular system, RC steering, 4 speed gearbox (sariel) and stepper (sariel). but I find the gearbox and stepper bulky at best not to mention difficult to shift accurately.

I believe your stepper will solve the accuracy of the shifts. I was able to reduce its size to 3 studs wide in order to replace Sarie's stepper on his gearbox. But I still find it too bulky. Your integrated design is beautiful and I would love to build it to incorporate it into my supercar. The shifting mechanism reminds me of the GT3. Have you been able to put together a video to build it? I would really like to incorporate it into my build.

[Attika]

I very much like your stepper mechanism. After building a few from varios different youtube videos, yours was absolutely genius in its simplicity and reliability. Currently, I am building my first supercar after getting inspired by the GT3, Koenigsegg One MOC and Aventador Pirelli Edition MOC that I have recently built. I have found that sheepo's modular system seems to be a good starting point for the chassis. At the moment I have managed to get a working remote control chassis using the modular system, RC steering, 4 speed gearbox (sariel) and stepper (sariel). but I find the gearbox and stepper bulky at best not to mention difficult to shift accurately.

I believe your stepper will solve the accuracy of the shifts. I was able to reduce its size to 3 studs wide in order to replace Sarie's stepper on his gearbox. But I still find it too bulky. Your integrated design is beautiful and I would love to build it to incorporate it into my supercar. The shifting mechanism reminds me of the GT3. Have you been able to put together a video to build it? I would really like to incorporate it into my build.

I'm glad you like the concept. I've just came back from my holiday and the next step is to make the instruction vid for this gearbox and stepper. Hopefully I can find the time in the next few days to make it. I'll link the video to my first post in this topic, so keep an eye on it.

[Charlieca00907]

Hey Attika

Any progress on the gearbox video?

[Attika]

Sorry, I'm busy this week. Have to wait till the weekend. Thanks for the interest and the patience. I wish I was a child again...

[Charlieca00907]

Last night I reverse engineered your gearbox/shifter. It was a bit of a challenge as I had to take a bunch of screen shots in order to understand it all. I found that the gears would jam similar to the gearbox from Sariel. So I decided to swap the white gear shifter connector (18948) with a red axel extension (26287). This allows the gear shifter ring to essentially have no friction. If this were a manual gearbox it would most likely "get out of gear" easily as there is no way to keep the shifter ring from unengaging. However, since the catches are held in position by the link arms/stepper it seems to mitigate this issue. I hooked up the gearbox to a motor and manually shifted gears with stepper and everything worked perfect. Tonight I hope to hookup a servo to the stepper to see if it works as I want it to.

I do have a technical question. What is the purpose of the differential in the gearbox. Is it for a 4 wheel drive?

[Attika]

Last night I reverse engineered your gearbox/shifter. It was a bit of a challenge as I had to take a bunch of screen shots in order to understand it all. I found that the gears would jam similar to the gearbox from Sariel. So I decided to swap the white gear shifter connector (18948) with a red axel extension (26287). This allows the gear shifter ring to essentially have no friction. If this were a manual gearbox it would most likely "get out of gear" easily as there is no way to keep the shifter ring from unengaging. However, since the catches are held in position by the link arms/stepper it seems to mitigate this issue. I hooked up the gearbox to a motor and manually shifted gears with stepper and everything worked perfect. Tonight I hope to hookup a servo to the stepper to see if it works as I want it to.

I do have a technical question. What is the purpose of the differential in the gearbox. Is it for a 4 wheel drive?

I've been turning the gearbox around in the video to help this reverse enginering. I'm glad you made it. I think it is also visible on the video that I was using the red, frictionles connectors too under the driving rings. It wouldn't work with the white ones. Yes it is a 4wd gearbox that is why it has two outputs. I've been using the yellow connectors for outputs. If you need a 2wd conversion just substitute the differential with a 16 and a 24 tooth gear by using a connector between them.

The red connector in the vid marks the input, but you can place the input to the other end of that shaft by changing the 3L axle with stop to a 4L axle. This is the very reason I did not align the stepper axle to the same level with the changeover catches.

If you experience the problem that the ball joints are moving out from the changeover catches, then use a tiny piece of paper or something to make that connection stiffer.

This is an actual prototype so there is or can be some design flaws. This gearbox isn't a "ready to publish" product, only a tool to demonstrate the stepper.

Anyway I hope you can use it succesfully in your supercar, and sorry again I couldn't get around the gearbox video yet.

[Charlieca00907]

Had to also make an impromptu mod as I didn't have the black part in one of the corners to make the gearbox sturdy. Also the oposite corner was loose so I added two parts so that the lever arm was firmly in place. I'll see if I can post a picture.

Edited September 8, 2016 by Charlieca00907

[Attika]

Gearbox instruction is inserted into my first post in the topic

[Charlieca00907]

I noticed on the new instruction video that you made some modifications that help with fixing the gearbox to the chassis. Also, I'm using a lego blue silicone band versus the green one you show. Is this an official lego band? if so, what is the part number.

[Attika]

Also, I'm using a lego blue silicone band versus the green one you show. Is this an official lego band? if so, what is the part number.

The green band I was using isn't Lego one, so can't give you a part number. I had a feedback from didumos69. He was using the red Lego bands: " I used two red silicon bands, one wrapped twice around the limiter and one wrapped once around the stepper." (quote from post No. 13)

What I can tell, if you don't have those bands, you can experiment with non lego rubber bands. The principal is that the limiters band should be stronger than the steppers band. There is plenty of way to adjust them, wrapping them around the ball joint, or twisting it on the stepper. It might take a 5 minutes of experimenting to find the right combination.

I couldn't resist seeing the demand, so here is a solution using original Lego silicone bands.

White on the limiter wrapped around both ball joint once.

DSC_2005 by Attika Moc, on Flickr[/img]

Part on Bricklink: http://www.bricklink....page?P=x37#T=C

Edited September 15, 2016 by Attika

[Charlieca00907]

The green band I was using isn't Lego one, so can't give you a part number. I had a feedback from didumos69. He was using the red Lego bands: " I used two red silicon bands, one wrapped twice around the limiter and one wrapped once around the stepper." (quote from post No. 13)

What I can tell, if you don't have those bands, you can experiment with non lego rubber bands. The principal is that the limiters band should be stronger than the steppers band. There is plenty of way to adjust them, wrapping them around the ball joint, or twisting it on the stepper. It might take a 5 minutes of experimenting to find the right combination.

I couldn't resist seeing the demand, so here is a solution using original Lego silicone bands.

White on the limiter wrapped around both ball joint once.

DSC_2005 by Attika Moc, on Flickr[/img]

Part on Bricklink: http://www.bricklink....page?P=x37#T=C

I will try that. I have the white, blue and red bands so it shouldn't be a problem.

[Charlieca00907]

Here is my chassis in progress. Its a combination of Sheepo's rear axel and your gearbox. I think I'm going to have to start from zero again. As I currently have it set up, the chassis still has too much flex which affects how the gearbox works especially in forth gear. Also, I've had to offset the gearbox in order to line up the motors. I'm probably going to have to make the chassis wider so that it "lines up" with your gearbox. Also, will probably use a new rear axel. I'm getting some inspiration from the BMW M4 DTM MOC. What I'm finding is that lining up the input and output of your gearbox is "a pain" but maybe that's because I'm going through the learning curve.

[Attika]

What I'm finding is that lining up the input and output of your gearbox is "a pain" but maybe that's because I'm going through the learning curve.

"a pain" Let say challenge... 4 speeders usually have offset in/outputs.

So as much as I see on the pic (it's pretty small, I've used magnifier) you worked out to build the input/output in center, what is a good approach. Me myself building it the same way. Finding out how to build a "stronger" chassis around it is really up to the concept of the MOC in your head, I can't help from the distance. If I find some free time this weekend I'lll build a motorised chassis too with this gearbox, but will use a pair of buggy motors. If I make any progress I'll post some pictures here hopefully those give you some hint or inspiration.

In my experience I need to build something 2-20 times to eliminate the flaws. It takes a master builder to come up with the perfect version for the first attempt. My fingers are crossed for you, don't give up, I appreciate that you gave the chance for this gearbox, I hope wont dissapoint you.

Some technical notes: Did you changed it to 2wd by not using the differencial? Also I wrote in the vid's description that it can take a limited torque. 2PF XL motors are likely to make the driving rings slip out. I'd be gad if you could share your experience later in this subject.

[Charlieca00907]

I left the differential in. I plan to power the fake engine that will sit in the front. I'm trying to build my personal sports car into a lego. In this case a Jaguar XKR. But I think the mock will be the XKR-GTS (its got more design elements that I can play with).

When powered up the 2xl motors after stiffening the chassis, I found that 1st-3rd [no load] worked fine. When I shifted into 4th it got a little more challenging. The shifting is also sketchy at times with "grinding" until it gets into gear. The XL motors (if I am not mistaken) are geared up to 36:20 into the input shaft. The output is unchanged. Your gearbox seems to be sturdy enough. Most of the problems I've had are "outside" the gearbox. I need to strengthen a few areas so that the gears don't slip out.

Hopefully this weekend, Ill get some time to go on to version 3.

[Attika]

I left the differential in. When I shifted into 4th it got a little more challenging. The shifting is also sketchy at times with "grinding" until it gets into gear.

That is exactly why I did ask you about the diff. If you noticed I was using 3 red clutch gears and 1 old type grey. The one that has direct connection with the differential shouldn't be the red becouse of the collar. The red has collar on both sides, the grey has only on the cluchside. It makes unwanted friction!!!!!

But before you change it consider this:

To power fake engine from the front output is ok. But if you use differential all the torque goes to the way of lower resistance, in our case to the fake engine and your car wont make an inch of a movement but the fake engine revs up. That is what a differential does. So here is the thing: You should exchange the differential to the 2wd version setup (16 and 24 gears+connector between them) and leave the red clutchgears as they are. Please check these things before you get forward.

[Charlieca00907]

I probably would have found out the hard way!! Thanks, I will incorporate that in version 3.

[Charlieca00907]

I was able to make a new rear axle to hook up to the transmission. It was a challenge in the sense that I had a lot of movement between the gearbox/rear axle/chassis. After stiffening a lot of areas, I was able to get it to work well under no load. When I placed it under load, Under load I notice quite a bit of grinding and also that even with 2 XL motors it wouldn't start from a standing start in 4th gear and barely start in 3rd. I removed one of the XL motors to see if it was just too much torque but that wasn't the problem. Then after taking moment to gather my thoughts before throwing the thing against the wall, I had a moment of "brilliance". I remembered that the rear axel that I am using (BMW M4 DTM by Bunojj) has the ability to change the gearing on the rear axle by swapping two gears, and viola! The car now has minimal grinding. Mostly on start, especially in 3rd and 4th. The only issue I have now is that I only have one servo motor which I'm currently using for steering. In what the servo gets here I may be able to change the steering using a regular M motor and use the servo to test the stepper.

I also made a mod to the stepper to keep the rubber band from coming off as it is making a gear change. I added a half pin with bar at the pivots of the stepper (top & bottom). This keeps the rubber band from coming off the arm as it "opens up".

BTW, how can I post photos larger than 100k? That seems to be the limit on this forum.

[Attika]

I was able to make a new rear axle to hook up to the transmission. It was a challenge in the sense that I had a lot of movement between the gearbox/rear axle/chassis. After stiffening a lot of areas, I was able to get it to work well under no load. When I placed it under load, Under load I notice quite a bit of grinding and also that even with 2 XL motors it wouldn't start from a standing start in 4th gear and barely start in 3rd. I removed one of the XL motors to see if it was just too much torque but that wasn't the problem. Then after taking moment to gather my thoughts before throwing the thing against the wall, I had a moment of "brilliance". I remembered that the rear axel that I am using (BMW M4 DTM by Bunojj) has the ability to change the gearing on the rear axle by swapping two gears, and viola! The car now has minimal grinding. Mostly on start, especially in 3rd and 4th. The only issue I have now is that I only have one servo motor which I'm currently using for steering. In what the servo gets here I may be able to change the steering using a regular M motor and use the servo to test the stepper.

I also made a mod to the stepper to keep the rubber band from coming off as it is making a gear change. I added a half pin with bar at the pivots of the stepper (top & bottom). This keeps the rubber band from coming off the arm as it "opens up".

BTW, how can I post photos larger than 100k? That seems to be the limit on this forum.

-Did you change the red cluchgear that is against the diff or did you remove the diff? One of these has to be done.

- You can use the M motor for the stepper with a rezurn to center mechanism or part: http://www.bricklink.com/v2/catalog/catalogitem.page?P=x928cx1#T=C

- For pics a host site needs to be used, like brickshelf or Flickr. Once you have your pic uploaded on the host site you can link it by clicking on the link icon above in the toolbar and paste the link in the box in that window.

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