8880 - Issues with build

[thekoRngear]

Guys, my 8880 was collecting dust for 2+ years. So, I decided to disassemble it. I kept the parts unassembled for a while and then I started rebuilding it (for it to collect dust for another 4/5 years). However, during the progress and after the build is complete, I have found that the Engine pistons are still moving while the car is in neutral mode. Is that normal? Am I missing something? 🤔

In my first build, I could not remember if I drove that car while in neutral mode.

[Stereo]

On 12/30/2023 at 9:52 AM, Verengard said:

By the way, there is also another minor issue with this set - the front and rear steering never allign straight, probably not possible to fix easily due to gear slack (rear is geared down).

A little late, but since I'm building it now - in step 20, the 16 tooth gear on the front steering rack needs to be engaged on the correct teeth - half of them are right, half are wrong, since only the 8 in the same spots as the 8 tooth gear will work right.  So what I do to get it aligned is install it with the 16 tooth gear not engaged with the rack, rotate the rear to centre, then push the 16 tooth gear into engagement.

The best they can be is 0.05 studs different, due to the gear rack geometry:

There's a 0.1 stud difference between the centerline of the axle and the centre of the valley in the gear rack's teeth that it uses, when the steering is at centre.  The 16t gear has twice the radius of the 8t, so any offset at the rear is doubled at the front.  So if the rear axle is exactly centred, the front is 0.1 studs wrong.  If the front axle is exactly centred, the rear axle is 0.05 studs wrong.  That's just in theory though, the slack between the two gears is a lot more than this.  If the front is on the wrong tooth, it'll be off by closer to 1 plate (0.4 stud)

If the steering went down the centre of the car it wouldn't have this particular problem, but it has to be offset to make space for the shifter.  Reasonable compromise I think, using gears to offset it would also introduce a bunch of slack.

 

I've been piecing it together with substitutions on all the single-set parts because I don't own them. Modern style hubs mostly fit, but they limit range of motion due to being a bit chunkier.  So for example the original 'flipping up pin-axle connectors' in this thread is not really an option, they would completely lock up the suspension travel.  I am using the original style 6.5L suspension arms, the new 5.5 ones would need pretty major modifications to work cause they have an axle hole in the exact wrong place.

[anyUser]

On 4/15/2024 at 4:52 PM, thekoRngear said:

I have found that the Engine pistons are still moving while the car is in neutral mode.
...
In my first build, I could not remember if I drove that car while in neutral mode.

I checked my model: If no gear is selected - e.g neutral mode = none of 1, 2, 3, or 4 engaged - the pistons are not moving if the car is moved forward or backward

[SNIPE]

51 minutes ago, anyUser said:

I checked my model: If no gear is selected - e.g neutral mode = none of 1, 2, 3, or 4 engaged - the pistons are not moving if the car is moved forward or backward

That sounds normal to me for a lego transmission. because the engine in a real car drives the wheels unless its in neutral,  but here the wheels are driving the engine, but its in neutral.

[thekoRngear]

1 hour ago, anyUser said:

I checked my model: If no gear is selected - e.g neutral mode = none of 1, 2, 3, or 4 engaged - the pistons are not moving if the car is moved forward or backward

Thanks for replying even though it has been ages. Thanks to AllanP’s valuable inputs it is now fixed. The driving rings seemed to have jammed a little whenever the gear switcher would change its position. It just wondered me that a very slight position changes of the connector(s) on which the driving rings are put on would cause the axles to spin.