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8110 steering and drivetrain problems


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#1 samuelwalpole

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Posted 21 August 2012 - 09:44 AM

Hi All,

I have just finished the chassis for the 8110 Unimog and I have encountered a problem! when pushing it forward the wheels turn to the right and when pushing it backwards they turn to the left so somehow the steering is connected to the drive shaft.

Despite being able to work out whats wrong, having looked back through the instructions it all looks right!

Could someone who may have encountered a similar problem please help cure my thickness!

Sam

#2 Aussie BJ

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Posted 21 August 2012 - 10:58 AM

I did the same thing the first time I built mine. You have missed a reverse symbol in the instruction and the centre diff is in back to front.

Brendan

#3 JunkstyleGio

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Posted 21 August 2012 - 12:39 PM

I guess ypu made a building mistake.
Please check out:

Buildingbook 1 (Submodel between step 15 and 16) page 20 and on..

You probably have built it something like this...

Posted Image

Edited by JunkstyleGio, 21 August 2012 - 01:06 PM.

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#4 Phantom59

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Posted 21 August 2012 - 12:59 PM

I made the same sort of mistake and only found it after I had finished the body. I had put the central diff in the wrong way  I end up taking the whole thing apart and stating over again  :cry_sad: :cry_sad: :cry_sad: :cry_sad:

Edited by Phantom59, 21 August 2012 - 01:03 PM.


#5 Aqualize

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Posted 21 August 2012 - 02:55 PM

On the topic of steering, I strayed from the Lego purist path. Because the steering is quite hard, caused by pin with ridges.
In the second book, page 47, step 15
http://cache.lego.co...12E4A5CECD4.pdf

Those 4 "Red Technic, Pin Long with Friction Ridges Lengthwise and Stop Bush" is causing the problem. I took the utility knife and pealed the ridges off on the lower part of the pins. Now steering works great.
This can easily be done when the model is finished so you can decide then.
Of course special care needs to be taken when dissembling it (which I haven't), so these pins doesn't enter the "general population". I will probably throw them away (I have bought many similar pins as extras via bricklink).

#6 Mbmc

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Posted 21 August 2012 - 03:36 PM

View PostAqualize, on 21 August 2012 - 02:55 PM, said:

the steering is quite hard, caused by pin with ridges.
In the second book, page 47, step 15
http://cache.lego.co...12E4A5CECD4.pdf
Those 4 "Red Technic, Pin Long with Friction Ridges Lengthwise and Stop Bush" is causing the problem. I took the utility knife and pealed the ridges off on the lower part of the pins. Now steering works great.

I don't think (only) those pins makes the steering hard. I checked on my 8110, and when it isn't stay on the wheels(no weight in the first wheels), the steering works fine and very easily. Primarily the reason for the hard steering is the lack of gearing down, there is 1:1 after the 12gear with the gear rack. The steering of the 8110 is VERY bad, the whole construction is badly designed with no gearing, the cv joint is prestressed by default. The "5,5L axle with stop" is too long for there.

It can be, that your pins caused more friction than the pins in my 8110, I'm not saying that you are wrong.

Edited by Mbmc, 21 August 2012 - 03:37 PM.


#7 JunkstyleGio

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Posted 21 August 2012 - 03:58 PM

View PostAqualize, on 21 August 2012 - 02:55 PM, said:

On the topic of steering, I strayed from the Lego purist path. Because the steering is quite hard, caused by pin with ridges.
....

Maybe you should have tried this little mod I did!
Posted Image
"Some say he eats ABS for Breakfast. Some say he dreams in Building Instructions. All we know is, he's called JunkstyleGio...."
Check out my LDD Brickshelf or my regular Brickshelf for anything technic.

#8 samuelwalpole

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Posted 21 August 2012 - 04:47 PM

Thanks for the help everyone, It was as first suggested, the center diff mounted the wrong way around!

I agree the steering is bad but I'll tackle that another day after I have actually finished building it. will probably leave it as is till I decide to motorize the steering.

Thanks again all :)

#9 Lipko

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Posted 21 August 2012 - 07:20 PM

Never ever steer when the car is standing. Every car driver should know that.

Really, the biggest cause of the hard steering is the friction of the tires. Today, we are too used to modern servo steering cars that's why we don't notice how hard is to turn the steering wheel on a standing car (and how damaging that can be for the steering linkage)

#10 RideFire

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Posted 22 August 2012 - 03:39 AM

View PostLipko, on 21 August 2012 - 07:20 PM, said:

Never ever steer when the car is standing. Every car driver should know that.

Really, the biggest cause of the hard steering is the friction of the tires. Today, we are too used to modern servo steering cars that's why we don't notice how hard is to turn the steering wheel on a standing car (and how damaging that can be for the steering linkage)

I disagree.  When the car is off, it is difficult to move the steering wheel.  When the car is on, it is easy to move the steering wheel regardless of motion.  The reasoning is modern cars have power steering to aid in turning.

In the case of the Unimog, removing the friction pins makes turning fairly easy.

#11 Mbmc

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Posted 22 August 2012 - 10:15 AM

Quote

Never ever steer when the car is standing. Every car driver should know that.
I agree, BUT the 8110 isn't a real car. Sometimes you HAVE TO steer when it is standing(like in a case of a real car), and as I wrote, the main reason for the hard steering is the lack of geraing down. The real cars(the ones with gear rack an pinion gear, or worm gear with no servo) have large gearing down. Ok, the steering itself in the first axle is hard compared to the other Lego cars, because of the large distance between turning point and the centre of wheel(as you wrote, this causes the lot of friction), and because of the friction pins.

Edited by Mbmc, 22 August 2012 - 10:17 AM.


#12 sqiddster

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Posted 22 August 2012 - 01:01 PM

I made the same mistake with the center differential... Definitely a pain to replace ;)

#13 Nazgarot

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Posted 22 August 2012 - 01:56 PM

View PostMbmc, on 22 August 2012 - 10:15 AM, said:

I agree, BUT the 8110 isn't a real car. Sometimes you HAVE TO steer when it is standing(like in a case of a real car), and as I wrote, the main reason for the hard steering is the lack of geraing down. The real cars(the ones with gear rack an pinion gear, or worm gear with no servo) have large gearing down. Ok, the steering itself in the first axle is hard compared to the other Lego cars, because of the large distance between turning point and the centre of wheel(as you wrote, this causes the lot of friction), and because of the friction pins.


No, the problem is not the gearing of the steering (even though that has a role to play) but the geometry. With correct geometry it would be a lot easier to steer, and LPE has made a mod to solve this. I haven't tried this yet as I was so displeased with the steering that I demolished the whole model for parts.

I was considdering to buy several 8110's, but I was so disappointed by the new hub part that I only bought 1. I was hoping for a part with a true knuckle/C-hub construction to get the pivot point as close to the wheel as possible, and maybe even introduce adjustable caster angel (+/- 15 degree, for so that you can use them both for front and rear axles). The new part did however move the pivot point even further form the wheel than the best MOC solutions for geared hubs...

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#14 Morj

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Posted 22 August 2012 - 03:55 PM

View PostMbmc, on 22 August 2012 - 10:15 AM, said:

...because of the large distance between turning point and the centre of wheel...

By the way, the distance between turning point and the centre of wheel is called  scrub radius.

#15 Mbmc

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Posted 22 August 2012 - 04:01 PM

Quote

the problem is not the gearing of the steering (even though that has a role to play) but the geometry
Yes, I wrote that:

Quote

the steering itself in the first axle is hard compared to the other Lego cars, because of the large distance between turning point and the centre of wheel

We talk about why is the steering hard, and has many reasons:

- geometry(but the axle has differential, that reduce the effect)
- the position of the axle(isn't horizontal)
- friction pins
- lack of gearing

The problem: with the steering gear in the top of the cabin is hard to steer. And for that the lack of gearing down is also responsible, as the geometry. We can talk about why is the steering in the axle hard, or why is the whole steering system hard. :classic:

Anyway I agree, the portal hubs could be better, for example Zblj's most used hub makes the pivot point closer to wheels, a simiar part could be designed for technic sets.

#16 Lipko

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Posted 22 August 2012 - 05:32 PM

View PostMbmc, on 22 August 2012 - 10:15 AM, said:

I agree, BUT the 8110 isn't a real car. Sometimes you HAVE TO steer when it is standing(like in a case of a real car), and as I wrote, the main reason for the hard steering is the lack of geraing down. The real cars(the ones with gear rack an pinion gear, or worm gear with no servo) have large gearing down. Ok, the steering itself in the first axle is hard compared to the other Lego cars, because of the large distance between turning point and the centre of wheel(as you wrote, this causes the lot of friction), and because of the friction pins.
It isn1t a real car but physics applies to it anyway. Rubber has high friction. Many Lego carts have this "problem", I guess 8110 is significantly heavier than those, that's the cause.

What I'm trying to say: too much "optimizing" of the steering may damage Lego parts.

Maybe I'm wrong though, it would be good to hear other opinions.

Edited by Lipko, 22 August 2012 - 05:32 PM.





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