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MangaNOID

[MOD] [HOWTO] Portal Hubs. Minimising slop/slack/looseness

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I'm fairly new to lego and this forum, so forgive me if this has been posted before.

I have been pretty disappointed in the hubs we get from LEGO sinse I started building the UNIMOG 8110 a few weeks ago.

the slop/looseness in the hubs is pretty bad. anyway cutting a long story short I found that you can minimise slop by maybe 90% just by not using the 3 pin bit that sticks in them.

photos explain better.

img_2134.jpg

normal 8 stop axel and with a 1L 'thingy' inside on the axel and then just put the wheel on. 

this also brings the portal hub in 1/2 stud closer lessening the bump steer, albeit a tiny amount.

img_2135.jpg 

its pretty sturdy but would love to get a micro bearing that fits over the wheel axle protrusion but inside the portal hub. 11mm x 7.5mm x 3mm would do it.

anyway I'm now excited about the UNIMOG again after almost giving up on it.

Edited by MangaNOID

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I think slop should be similar to the technical term clearance or slack. As in sloppiness/loose.

edit: Correction of a word. And Didumos you were faster!

Edited by AkiyamaWataru

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Nice idea! The only problem I see is that the wheels are not secured and will slowly slide off the axle.

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good point Didumos69. although a lot of home made portal axles are the same wheel slip on design.

also I just tried, as you mentioned it, and lifted 1090g  with the wheel by picking up the axle, and no movement on the axle. any more weight created slipping. you could also add more axel bits on the outside of the wheel to hold it if slipping does occur?

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34 minutes ago, MangaNOID said:

good point Didumos69. although a lot of home made portal axles are the same wheel slip on design.

also I just tried, as you mentioned it, and lifted 1090g  with the wheel by picking up the axle, and no movement on the axle. any more weight created slipping. you could also add more axel bits on the outside of the wheel to hold it if slipping does occur?

Indeed, many custom wheel hubs suffer from this issue. You could indeed add half bushes, but eventually - after some playing around with the model - you will get slack in such setups too. The point is that the wheel and half bushes only need to slide a fraction of a mm to introduce substantial slack.

Nevertheless, this remains to be a great idea, also because it reduces the wheel offset.

Does the wheel actuallly touch the outer circle of the portal hub? If it does, I can imagine this really works great!

Edited by Didumos69

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I have reduced the wobble in the wheel hub by using 0,3mm thick teflon washer between the hub and axle (on Claas hubs). Maybe the portal axles would require different thickness of the washer. Teflon is also more slippery so its win-win. I have bought a sheet of teflon film in size 10x10cm/0,3mm for about 1€ and cut the washers out of it.

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34 minutes ago, Didumos69 said:

Indeed, many custom wheel hubs suffer from this issue. You could indeed add half bushes, but eventually - after some playing around with the model - you will get slack in such setups too. The point is that the wheel and half bushes only need to slide a fraction of a mm to introduce substantial slack.

 

good point. especially if one is rock crawling, and then it could end up worse than normal portal hubs. 

also the wheel does touch the outside of the portal and then the wheel does not turn well so this is where you have to create a bit of a gap like usual on axles.

I also tried one of these little wheels which fit perfectly inside. you can now have the wheel hard up against it for zero slop but obviously the wheel now has a small contact area and that setup feels flimsy. plus the offset is then increased.

img_2133.jpg 

21 minutes ago, Ivan_M said:

I have reduced the wobble in the wheel hub by using 0,3mm thick teflon washer between the hub and axle (on Claas hubs). Maybe the portal axles would require different thickness of the washer. Teflon is also more slippery so its win-win. I have bought a sheet of teflon film in size 10x10cm/0,3mm for about 1€ and cut the washers out of it.

great idea Ivan! I tried a bit of plastic but it was too thick and the wheel barely moved. I will try this. have your hubs held up ok...i.e they haven't re-slackened?

Edited by MangaNOID

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Yes the connection is very strong. The wobble is still there as claas tires are in my opinion too big for lego, but it is much better compared to stock solution. I would make some pictures but there is absolutely nothing to see. The film can be bought here in various thickness: http://www.jatagan.eu/en/make-a-knife/teflon/

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1 hour ago, MangaNOID said:

good point. especially if one is rock crawling, and then it could end up worse than normal portal hubs. 

also the wheel does touch the outside of the portal and then the wheel does not turn well so this is where you have to create a bit of a gap like usual on axles.

I also tried one of these little wheels which fit perfectly inside. you can now have the wheel hard up against it for zero slop but obviously the wheel now has a small contact area and that setup

Maybe you could use this2958.pngpart as a spacer between the wheel and the hub. It is very smooth and could sit right against the hub without causing too much friction, I think. Or this belt wheel:4185.png, which could be attached to the wheel with pins..Using the surface of the outer circle of the hub would help reducing slack.

Edited by Didumos69

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yes the gray wheel with pins works well but the offset is increased again more than standard hubs...stupid compromises.

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8 hours ago, MangaNOID said:

img_2133.jpg

I have found a more efficient way of doing this, granted its not Lego but a 4x11x4mm bearing fits perfectly in the spot you put the mini wheel piece, the bearing will make it run very smooth and be flush on the flat part.

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Good to hear bearings work. Yes it's a bit un-pure but when hubs are so wobbly what does one do.

i'd prefer a 7.5mm ID of the bearing though as then the wheel axle protrusion sits inside the breathing and hub creating better offset.

or to keep it Lego one could drill that little wheel in the portal hub out to 7.5mm ID and half the wheel to a 1/2 L for the best compromise, if that makes sense?

otherwise the first style in the first post with the 1L spacer works really well as I tried on the vehicle last night. Very happy!

Edited by MangaNOID

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Portal axle hub is to wide anyway and steering radius is bad, but praise for your good intention for one of biggest problems that we have with LEGO Technic last years.... With the time 1/2 bushes will get loose...

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1 hour ago, I_Igor said:

With the time 1/2 bushes will get loose...

What he said.

This is the best way to secure this type of wheels to an axle that I found so far. Mild beatings that will normally loosen the 1/2 bushes over time are completely absorbed. Only severe stressing will cause the squeezed rubber connector to slide:

800x450.jpg800x450.jpg800x450.jpg

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Just now, Didumos69 said:

What he said.

This is the best way to secure this type of wheels to an axle that I found so far. Mild beatings that will normally loosen the 1/2 bushes over time are completely absorbed. Only severe stressing will cause the squeezed rubber connector to slide:

 

I understand that, but steering angle is going from bed to worse if you understand what I mean :wink:

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1 minute ago, I_Igor said:

I understand that, but steering angle is going from bed to worse if you understand what I mean :wink:

Just now, Void_S said:

You can put it at the outer side of the rim, not between the rim and hub :sweet:

On the outside. That was how I intended this. :thumbup:

 

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Just now, Didumos69 said:

On the outside. That was how I intended this. :thumbup:

 

that make more sense gentleman... :thumbup:

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nice outside hub idea Didumos69!

I've been putting the portal hub setup with just the wheel through some extra sideways hand forced treatment on the suspension with some of those typically used RC tires on. these wheels aren't slipping anywhere in a hurry.

also you make me realise that the 3L pin comes in black! now I need to order a few hundred of these as I hate the blue pins!

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