Brick Track Parts: Types, Sizing and Tensioning for MOC Tanks
Short version: for a tank or a construction vehicle MOC, tracks come down to three things — picking the right track type, getting the link count right, and setting tension properly. A small track link measures about 1 cm, a large link about 2 cm. Rubber tracks grip well but age; plastic tracks wear well but run stiff. On budget, a 60-link plastic track runs roughly 15–25 yuan, and rubber versions cost 30%–50% more. Buy links based on twice the hull circumference, keep 2–4 links spare for tension adjustment, and you will usually get it right the first time.
1. Track types: small vs large, rubber vs plastic
Brick tracks come in two sizes. Small tracks are about 1 cm per link and are mostly used on small and mid-size tanks and armored cars, where the build needs to stay compact. Large tracks are about 2 cm per link and suit excavators, bulldozers and other construction machinery, giving a much heavier visual presence.
Material splits them again. Rubber tracks grip hard and run quietly, which makes them good on carpet or smooth flooring, but sun and heat will make them brittle within three to five years. Plastic tracks resist wear and hold their dimensions, at the cost of stiffness and a bit more noise. If you are new to tracks, start with plastic.
2. Pairing tracks with the wheel set
A track only transmits drive when it wraps the drive sprocket and the idler. The drive sprocket is the toothed hub, and its tooth pitch has to match the holes on the inside of the track. The idler keeps tension and guides the track; you normally run one pair front and one pair rear, with road wheels in between to carry the vehicle's weight.
The general rule: small tracks take small wheels of 2–3 cm diameter, large tracks take 4–5 cm wheels. The axle spacing between the front and rear wheels should be slightly shorter than the total track length so you have tension room to play with — that is what keeps the track on when it runs. A common layout puts the drive sprocket at the rear and the idler at the front, which makes a tank more stable when reversing up a slope.
3. Working out the link count
There is a simple rule of thumb: total links ≈ 2 × (center distance between front and rear wheels + drive wheel radius × 3.14), divided by the length of a single link. For example, with a 20 cm center distance and a 2 cm drive wheel radius on 1 cm small track links, the circumference is about 2 × (20 + 6.28) ≈ 52.6 cm, so you need 52–53 links. Order 55 links and use the 2–3 spare ones for tension.
Always buy a few links extra rather than aiming for an exact fit. A track that is clamped tight will throw itself off as soon as the model moves.
4. Tension adjustment
Tension is where track MOCs most often go wrong. Once assembled, press the middle of the track with a finger: if it depresses around 0.5 cm, and the drive sprocket turns without slipping or throwing the track, you are in the right range. Too loose and the track comes off; too tight and it stalls the motor.
To adjust, move the idler's mounting holes forward or back, or add 1–2 shims of 0.5 cm thickness at the tensioner wheel. After fitting the motor, run it at low speed unloaded for 1–2 minutes to bed everything in, then test on the ground and on a slope.
5. Common MOC applications: tanks, excavators and Technic
Tanks and excavators are the classic track builds. For a 1:35 scale tank, track width is around 1–1.5 cm — use small tracks with independent suspension and shock absorbers. Construction machinery calls for large tracks paired with a Technic gearbox and motors, so you can drive the model and cycle the bucket from the same drivetrain. When you connect a track wheel set to a Technic cross-axle, make sure the axle goes into the cross hole at the center of the drive sprocket and is locked in firmly.
Before you build, search for track builds on brickplan.cn and look at how other people laid out their wheel sets on the same subject. It saves a lot of rework.
FAQ
Q: How do I choose brick tracks without buying the wrong ones? A: Measure the drive wheel diameter and the vehicle width before ordering. Small tracks at about 1 cm per link suit tanks; large tracks at about 2 cm per link suit construction vehicles. The hole pitch inside the track must match the sprocket tooth pitch, or it simply will not fit.
Q: How long is a single track link? A: A small link is roughly 1 cm long and 1 cm wide; a large link is roughly 2 cm long and 2.4 cm wide. Work out the total before buying: circumference is about twice the front-to-rear wheel center distance plus the drive wheel circumference.
Q: Are domestic brick tracks compatible with LEGO? A: The vast majority of domestically produced brick tracks follow the LEGO standard, with matching tooth pitch and hole spacing, so they can be mixed directly. A few older molds are slightly off-dimension, so check reviews confirming compatibility with LEGO drive wheels before you buy.
Q: The track is loose and keeps coming off — how do I tighten it? A: First move the idler's mounting holes forward, or add 1–2 shims at the tensioner wheel. The standard is about 0.5 cm of deflection at the middle of the track, with no slipping or throwing when you turn the drive wheel. Too tight stalls the motor, too loose throws the track.
Q: Rubber or plastic tracks — which is better? A: Rubber grips strongly and runs quietly but ages, going brittle in three to five years. Plastic resists wear and holds dimensions but is stiffer. For display and for getting started, choose plastic; if the model runs a lot on smooth floors, rubber is the better fit.