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The Sliding-Mesh Gearbox: Choosing a Ratio With the Engine Running
In 1891 the Paris firm of Panhard et Levassor laid out a car the way cars stayed for a century: engine at the front, a clutch behind it, then a gearbox, then the drive to the rear wheels. Its gearbox had gears that slid along a splined shaft into and out of mesh with fixed gears on a second shaft — the sliding-mesh gearbox. Émile Levassor is often quoted describing it as brutal, but it works.
It exists because an engine only pulls well over part of its speed range. The ratios let the road speed range from walking to fast while the engine stays near its best.
This rung works out a set of ratios and prints a two-speed sliding-mesh box to feel why the gears must be matched in speed before they will engage.
中級者
About 4 hours
手順
1
1
Choosing the ratios
Choosing the ratios
Jupyter ノートブックを読み込み中…
2
2
Print a two-speed sliding-mesh box
Print a two-speed sliding-mesh box
Print two shafts' worth of spur gears in PETG with module 2 teeth: on the output shaft, a 30-tooth and a 20-tooth gear joined as one sliding block with a square bore, riding on a square steel shaft; on the input (lay) shaft, fixed 15- and 25-tooth gears on a round shaft with a grub screw each. Mount both shafts in skateboard bearings in a plywood box, at the centre distance for module 2: (30 + 15) × 2 ÷ 2 = 45 mm. Check the other pair gives the same distance: (20 + 25) × 2 ÷ 2 = 45 mm.
Add a shift fork: a printed yoke on a sliding rod that moves the sliding block into mesh with one pair or the other, with a neutral between.
このステップの材料:
PETGフィラメント150 g
鋼の棒材2 個
スケートボードベアリング4 個
合板1 枚
小ねじ8 個必要な工具:
FDM 3D プリンター
デジタルノギス 6インチ
六角レンチセット
コードレスドリル
ドリルビットセット3
3
Feel why the speeds must match
Feel why the speeds must match
Drive the input shaft with the cordless drill at a steady low speed, output shaft free. Engage first. Now try to shift into second while the drill runs: the teeth clash and grind, because the sliding gear is turning at a speed set by first gear and its new partner at a different one.
Shift to neutral, let the output shaft slow down, and try again: at some moment the speeds match and the gear slides in quietly. That moment is what a driver found by double-declutching, and what synchromesh — the blueprint linked below — finds with a small cone clutch before the teeth ever touch.
Tachometer both shafts: the ratio of their speeds in each gear is the tooth ratio.
必要な工具:
コードレスドリル
デジタル回転計
透明保護メガネ4
4
History and context
History and context
**Panhard et Levassor, Paris, 1891** — the front-engined layout with clutch, sliding gearbox and drive to the rear, the 'système Panhard'. No patent number is asserted here.
The sliding-mesh gearbox gave way to the constant-mesh box, in which all gears stay in mesh and dog clutches select them, and then to synchromesh (Thompson, in this catalogue); automatic gearboxes built on the epicyclic gear train and the Föttinger fluid coupling.
**Honest limits.** Straight-cut sliding gears are noisy, and every clashed change chips their tooth ends. Changing gear needs skill. And the power is interrupted during every change.
材料
5- 150 gプレースホルダー
- 2 個プレースホルダー
- スケートボードベアリング10%コミッション4 個プレースホルダー
- 1 枚プレースホルダー
- 8 個プレースホルダー
関連ブループリント
これらのブループリントは知識を共有しています — 技術、材料、原理
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