[HELP] Adders

[Buddy010702]

So I'm trying to build a Adder for my new creation, because I need a lot of torque and I would like quite a bit of speed. I have tried to build one, and need some help.

So can people help me? Is this the right setup? Should I use knob wheels or the grey gears in there?

When I tried to drive it it the XL motors are fine, but the L motors seem to be jumping out of the bevel gears in the differential (see picture 2) anyone know how to fix this? 

Edit: Knob wheels don't seem to help, I rebuilt a tiny bit, but, when engaging L motors, it doesn't seem to help... Would the motors be too weak?

 

Any tips?

 

Thanks in Advance

 

 

Edited September 29, 2016 by Buddy010702

[Andy D]

Can you post your photos on Flickr so they will show in your post.

I can't see your photos, but I built an subtractor (I believe it is the same as an adder, check it out) using Sariel's longitudinal subtractor and it seemed to work quite well. You can find a schematic on page 282 of his book. I highly recommend his book, and it has a whole chapter on adders and subtractors.

IHTH

Andy D

 

[Buddy010702]

48 minutes ago, Andy D said:

Can you post your photos on Flickr so they will show in your post.

I can't see your photos, but I built an subtractor (I believe it is the same as an adder, check it out) using Sariel's longitudinal subtractor and it seemed to work quite well. You can find a schematic on page 282 of his book. I highly recommend his book, and it has a whole chapter on adders and subtractors.

IHTH

Andy D

 

Thank you, I do have Sariel's book and it is very useful, I guess I will sign up for bricksafe, hopefully that will work :/ From what I've read a Subtractor and Adder are similar, but have slight differences. 

The issue I have is using Unimog deulies for drive with out being able to drive the front drive. Guess time for another rebuild...

[MRP_]

have you considered using a system like this?

 

[Victor Imaginator]

7 hours ago, Buddy010702 said:

When I tried to drive it it the XL motors are fine, but the L motors seem to be jumping out of the bevel gears in the differential (see picture 2) anyone know how to fix this?

Looking at photos it's not clear what exactly cause this. If axle is sliding out - using some axle with stop should help. If whole block of LBG gears and L-motors moving out - additional bracing should help.

[davebarrett]

Have you tried using this part?

 

https://rebrickable.com/parts/99008/technic-axle-4-with-centre-stop

[Buddy010702]

10 hours ago, MRP_ said:

have you considered using a system like this?

 

No, I haven't considered one like that, but that's basically what I want, thanks! From what I see, one XL motor engages first, then the other? And that speeds it up? Am I correct?

[TheMindGarage]

At the moment you should have:

• Casing rotates at ~100RPM with 2.8 XL motors of torque
• One shaft rotates at ~250RPM backwards (if this shaft is rotating in the same direction as the casing, you're losing power) with 2 L motors of torque
• Output rotates at ~450RPM.

But if you apply a load to the output, the Large motors will stall well before the XL motors do. In fact, I'd go as far as saying that the Large motors will get driven backwards if you apply a load. Basically this will happen:

• Casing rotates at ~100RPM
• Output stalled to 0RPM
• Shaft with L motors gets forced to rotate ~200RPM forwards

I would recommend replacing those three 16-tooth gears with a 12:20:12 combination or possibly even 8:24:8. This will mean that both inputs of the adder get similar torque and will prevent this situation of one input forcing the other. You can always gear up after the adder.

[MRP_]

11 hours ago, Buddy010702 said:

No, I haven't considered one like that, but that's basically what I want, thanks! From what I see, one XL motor engages first, then the other? And that speeds it up? Am I correct?

yup, exactly! and if you wanted, you could make it 3 speed by having the output form the differential go into the side of another differential, with another motor setup on the other side.

btw what are you building? it looks massive, I'm curious! or is it a secret?

[davebarrett]

In my experience, more diffs = loss of torque.

I built something like the attached, with another diff combining the output of the motors again. Just pushing this not much more than this, four tyres, and a battery box, with no gearing up or down, didn't work.

Edited September 30, 2016 by davebarrett
Add attachment

[Buddy010702]

17 hours ago, MRP_ said:

yup, exactly! and if you wanted, you could make it 3 speed by having the output form the differential go into the side of another differential, with another motor setup on the other side.

btw what are you building? it looks massive, I'm curious! or is it a secret?

Thanks for showing me it! I build it and It works exactly how I wanted it to! I don't think I need any more speeds, but thank you for the suggestions. I wanted to keep this project a secret until I could make sure It worked, so I will say it in the spoiler below. I have too many projects that don't really make their full way, due to lack of motors and such... So I'm trying to cut down on that (although I already posted a  few earlier versions on my Instagram...) Anyway, I have plenty of room, so I want to add a few more functions.

Spoiler

It's the Tumbler from the Dark Knight Trilogy, I know a lot of people have built this, but I want a lot of functions, and to bring new things to the table. I feel like I want to bring something new to the table, especially when I build something built so often.

Planed functions:

1. 2 speeds + spinning fire 
2. Four pairs of lights
3. Steering (need to work on it a tiny bit (First time I've had problems with Lego hubs :/ ))
4. Shooting Canons (like Sariels)
5. Possibly manual opening door mechanism
6. Full suspension
7. Possibly more manual functions (any suggestions?)  

 

6 hours ago, davebarrett said:

In my experience, more diffs = loss of torque.

I built something like the attached, with another diff combining the output of the motors again. Just pushing this not much more than this, four tyres, and a battery box, with no gearing up or down, didn't work.

Yeah, not sure if I will try to build a adder like above ever again, especially when after I found out after testing it that I had bent some of the teeth in a bevel gear in the diff. I guess I hadn't realised how powerful XL motors could be, especially when I had only had one previously, I ordered two more for this model... 

[MRP_]

since you want to keep it kinda secret, I'll hide my question 

Spoiler

I've tried to build the tumbler multiple times in the past, but always get stuck on the steering! what are you planning on doing? I would do sariel's method, but I don't have the pieces needed. fyi this is sariel's https://www.youtube.com/watch?v=yUTD9z-aiHU

 

 

[Buddy010702]

I will post more in the spoiler, but long story short, it works, but doesn't work too well...

 

Spoiler

I have taken the steering from this Forum from jovel, but the issue is, when combined with a servo motor it has a tiny steering angle, the somewhat long body on the tumbler, and the play of the lego hubs makes the tumbler turn very poorly. 

I could probably build Sariel's as I own the set 9392, which if I'm correct has the parts to build it, but if I'm correct the steering isn't independent, so I think I'm going to try a modified version of it. If a modified version Sariel's doesn't work, I'm going to try more of the steering ideas from the Forum above. I have looked at many tumblers, and lots of them don't have elegant designs, or look too weak, so yeah, steering may be difficult...