Not-so super Lego Technic car, what I’ve learned so far

And so my endeavor with Lego Technic continues. Still wanting to fulfill my childhood dream of building a Lego Technic car, I’ve started buying parts from BrickLink. My goal is quite straight forward; build a car with these simple specific mechanical functions:

• Independent suspension (who doesn’t want this?)
• All wheel/four wheel drive
• Real working steering wheel mechanism

I had a fourth requirement; all wheel steering, but decided to cancel it off for now. And that’s it, simple.

I later added one other thing; Power Functions.

By the way, the last time I played with Lego, there was no such thing as studless Technic bricks. But it didn’t take me long to get familiar with it. I have to say, the studless system has its limitation but the advantage is far greater, the best being everything is simply multiple of 1 unit.

Anyway, coming back to my effort, here’s a picture of my first attempt at building a car:



Overall, it’s very flaky. The only part of the car that is good is the rear as I spent days working on it. The mid and front part, took me only half a day because I was so eager to get this thing moving. And it did. Well, partially anyway. As you can see on the top right of the photo, the Power Functions’ battery pack is on and I have one XL motor in it, so this baby can move, but only forward and backward because, if you look closely, the steering is not done yet.

Here’s a few more photos:

The rear part. I took some effort in ensuring all the Power Function parts are easily removable. Interestingly, the battery pack becomes the car’s structure, forming a rigid part for the suspension to press on to.	One XL motor is marginally enough for this model. I have to get another XL motor.
This is actually a top view of my car. Clearly very empty. It looks like the undercarriage of the car.

So, what have I learned so far?

1. If you have a heavy model, don’t use bevel gears in perpendicular setup to transfer power from motor to gear box. If you do, at least make sure if you have enough counter gears, because under high stress, the driver gear will jump a tooth or two before the follower follows. The better option is to use knob wheels.

No.	Yes.

2. More gears is better. Yes, more gears will introduce more friction and as such will lose efficiency, but what I've found, using more gears will provide higher durability and add some needed sturdiness. Example shown below. Originally, the drive shaft connects directly to the input gear of the differential via a universal joint. Simple, yes. Durable, not. In the setup shown below, redundant gearsets are used and I've found them to be much better and more reliable at transferring power to the differentials.



3. Use shorter shafts where ever possible. Lego, as you might have been aware, are made of plastic. So, the longer axles are somewhat prone to torsion effect. Another way to counter torsion effect is to again use redundant gearsets that are spread apart along the axle.

After a ‘successful’ run, I have taken my model apart to fix known issues, and hopefully, the second version will be much better. I’ll report back soon.

-Wan Khairil Reza-

Lego Technic 9392 Quad Bike Review (and Mod)

If you've read my previous post, I've recently made it back to world of Lego. My first come-back set is the 2012 Lego Technic quad bike (9392).

Pic 1: Lego Technic 9392 Quad Bike

It is a decent Lego Technic model. Building it was without any problem. I didn't time myself, but I'm sure it was less than 10 minutes.

Overall, I like it. It captures the essence of a quad bike. The big wheels, the body panels, the bouncy high suspensions and this model even has a chain linking the dummy engine to the rear axle. What I love the most is the front suspension; good travel and works nicely.

But one thing that I'd rate poor is the steering. It is loose with lots of free play and is not center balanced. Makes it hard for the quad bike to stay straight. This is due to so many loose joints in the steering design.

 
Pic 2: Loose joints that contributed to lousy steering

Another thing that I consider a design mistake in this model is the location of the swingarm’s pivot axis, which affects the tension of the chain. In real world situation, a chain's tension is kept constant by ensuring that the distance between the drive sprocket and the wheel sprocket is kept constant. Otherwise, it might cause the chain to become loose or break. To achieve this, the drive sprocket must be on the same pivot axis as the swingarm. But this is not the case for Lego Technic 9393 quad bike. Pic 3 shows the location of the drive sprocket axle and the swingarm pivot point.

Pic 3: Default 9392 Swingarm setup

Pic 4 and Pic 5 show that the chain becomes loose when the rear suspension of the quad bike is pressed.

Pic 4: Chain in normal condition	Pic 5: Chain becomes loose wen rear is pressed

I have to solve this two issues.

First, the swingarm. I modified it so it pivots at the same axis the drive sprocket. I added or removed as few pieces as I could and I reused as much as possible. Pic 6 shows the moded design. And as can be seen in Pic 7 and Pic 8, the chain's tension is maintained when the rear suspension is pressed. Success.

Pic 5: The redesigned swingarm

Pic 7: Chain in normal condition	Pic 8: Chain doesn’t become loose when rear is pressed

Next, the steering. I noticed the toe of the front wheels are going slightly outwards and it gets worse when you push the bike forward. I used this to my advantage. What I did was I flipped the whole front part of the quad bike, as shown in Pic 10. By doing this, I turned the toe inwards. The steering arm is also now at the back.

Pic 9: The original steering design	Pic 10: The modified steering design

Pic 11: The original steering design, with outward toe	Pic 12:The moded steering design, with inward toe

The inward toe actually straightens when pushed forward and does make the bike go in a straight line! Nice. to finish off the steering, I also used a universal link to give the handle bar a slight angle. Success.

Pic 13: Universal link on the steering

The moded final model is much better. I wonder if I can motorize this with a Power Function.

Pic 14: My version of Lego Technic 9392

Wan Khairil Reza

My first two-speed (then four) Lego Technic gearbox design

Last weekend I took to myself to design my very first Lego Technic gearbox. I set a simple goal; a two-speed gearbox with 1 input axle, 1 output axle, and no gear grinding allowed.

I'm still at the very early stage engaging in this Lego Technic hobby and I'm only beginning collecting my Technic parts. As such, unfortunately, I don’t have enough parts available to build an actual Technic gearbox. Luckily, Lego provides a useful tool to help people virtually design their Lego projects. It is the Lego Digital Designer (LDD) and it is downloadable totally free from Lego's website. Even though LDD is not as flexible as I wish it could be but it is good enough for most design tasks. The learning curve is not steep, provided you have some foundation in Lego building. Good mouse dexterity would come in handy as well.

In this blog post I want to share my process in designing my gearbox, using LDD for now and hopefully with actual Lego Technic parts soon.

First, being a newbie, I figure I need to study Lego gear pairing. The screenshot below shows what I did in LDD. The objective here is simple; to see how various pair of gears can be positioned, since Lego designing is generally constrained by the number and position of the studs and holes of Lego bricks. So, I tried out a few combinations and roughly got the idea. I also found the site that helps in Lego Technic gear pairing.

Pic 1: Gear pairing exercise

 

Next step, I went straight to designing my gearbox. By the way, if you need to understand how gearboxes work, refer to How Stuff Works or here for Lego gears tutorial.

The screenshot in Pic 2 below shows what I did. I decided to lay it flat first, in order to see how the gears would be arranged and linked. As I've mentioned, I don't want gear grinding during shifting, so I use the driving ring that allows me to lock on to either one of the free wheeling gears.

Pic 2: The gearbox, flat

Basically, the gearbox provides a gear down from a 12 teeth gear to a 20 teeth gear (1:667) shown with green gears and a gear up from 20 teeth to 12 teeth gear (1:0.599) shown with grey gears. Because my design is laid flat, with very little effort you can trace the gear and axle movement of each speed setting, as shown in Pic 3.

Pic 3: Gear one and gear two

Now I know what I needed, next would be to simplify the design. Just like most things in engineering or computer programming, some components can be reduce, reuse or shared. After a bit of fiddling, I got this:

Pic 4: My two-speed gearbox

Pic 5: My two-speed gearbox, bottom view

Simply, the flat gearbox is ‘folded’ so that the gears and axles are layered. I've also combined the output axle, and made it compact. And just like that, I've completed my task. I’ve designed a two-speed gearbox. I can now go and watch The Big Bang Theory.

But I didn't.

This is too simple and too easy. I also looked at my gear ratios and it was clearly unrealistic.

If I can make a two-speed gearbox, surely I can make a four-speed version. The simplest thing to do is just to replicate my two-speed gearbox, and change the gear pairing to have different ratios. And that's exactly what I did.

Pic 6: Two two-speed gearbox

Now, the available gear ratios are:

1st gear 1:3
2nd gear 1:1.667
3rd gear 1:1
4th gear 1:0.599

But by having two two-speed gearbox, I now have two input and two output axle. So, the simplification cycle starts again. With a little rearrangement, and a few extra gears, Pic 7 is what I got:

Pic 7: Final four-speed gearbox

The final design fulfills all my requirement. It's a 4 speed, 1 input, 1 output, absolutely no grinding while changing gears. Can’t wait for my Lego Technic parts to arrive!

Am I done? Yes for now, but I can see a lot of gaps in my design. I'm sure seasoned Lego Technic designers would take one look at this, smirk and point out what I should have done. And I hope they do, so please, share your thoughts.

- Wan Khairil Reza -

Reignited love (and hope) for Lego

Having a child of your own will open up new life changing experiences and might also rekindle some of your childhood interest. Now, having 4 boys will put this so called experience into overdrive. One thing that got reignited (extremely) for me was my love for Lego.

Very brief personal history; My brother and I had a decent amount of Lego when we were kids. Mostly the normal Lego bricks. I can still recall most models when visiting the Brickset website. The grandest thing I had was a Lego space solar transporter (6952), which dad bought when I was 9. And also one (yes, one) Technic set, a roadster (8832). Then, I grew up and all was gone; literally. Gone because dad decided throw (mom said he gave it) away my old toys as it was taking up space and I wasn't living there since I was 13. I'm not angry at all at my dad, though I wish he had done otherwise. But it IS his house and it was his money that bought all those Lego. And just like that, Lego was nothing more that a childhood memory.

Fast forward to the future.

On my eldest son's first birthday back in 2005, his grandmother (my mom), bought him a box of Duplo. He immediately loved it. From then on, his (or should I say, our) Lego collection grew and grew. From Duplo to Lego bricks to Lego theme sets. As my children's interest grew, so did mine. Add to that the easy and friendly Lego website plus fan sites such as Brickset and YouTube videos that gave access to more information and introduce other Lego fans. And now, in less than a month, Legoland Malaysia will open its doors and it's only about 20 minutes away from our house!

All these have put my love and interest back in Lego.

As a toy, Lego is a toy that can give you other toys. Want a robot? A car? Voltron? A dagger? Your own town? You can just make one for yourself, by yourself.

But Lego is also more than a toy. It's a tool for learning. A tool for turning imagination into reality. It can be art. And yes, you can even collect the rare ones for trading if you like.

And this is something I wish and hope that more of my fellow Malaysians will see, realize and embrace. With the opening of Legoland Malaysia, I hope the younger people will be encouraged to delve into the world of Lego and allow their creative mind to grow and develop further. Even though Lego are relatively expansive, you do get high quality products and an extremely cohesive eco-system, which means you can re-use your Lego from the past and into the future. Consider it an investment.

From the simple toddler friendly Duplo to Lego bricks to the more sophisticated engineering-ish Technic, Lego offers a lot in developing creative mind.

Here's my wish list for Lego in Malaysia:

1) To have local Lego workshops and exhibitions

2) A more active and involve local Lego fan club

3) Get schools to have Lego competitions, activities or even some sort of Lego Day

These can be done and I hope I can be part of it.