Heinrich Lanz D 7531
Built: 1935–1941 · Series: HN 3
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Heinrich Lanz HN 3 - the Bulldog with a hot-bulb single cylinder: D 7500 to D 7531, 4.8-litre displacement, 18.3 kW at 760 to 850 rpm, multi-fuel operation
Since 1921, the Lanz Bulldog had epitomised the slow-running hot-bulb single-cylinder engine: a horizontal two-stroke with a pre-chamber whose hot bulb was heated with a blowlamp before starting and which then sustained combustion without spark ignition. The HN 3 series, with types D 7500 to D 7531, belongs to this Bulldog family, built by Heinrich Lanz in Mannheim; the four-digit number after the D distinguishes the individual versions of the series.
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The register lists 6 versions with a uniform 18.3 kW from the single-cylinder engine of 4,767 cm³, kerb weights of 1,980 to 3,240 kg, lengths of 2,735 to 2,935 mm, widths of 1,524 to 1,700 mm and heights of 1,785 to 2,030 mm at speeds of 760 to 850 rpm; every model runs as a multi-fuel engine.
The low-revving hot-bulb engine made the Bulldog a multi-fuel unit that, besides diesel, could also burn crude oil, tar oil and other hard-to-ignite fuels - a decisive advantage in regions without a reliable diesel supply, which made the Bulldog an export success worldwide. Its characteristic, far-carrying slow chugging at low revs shaped the sound of agriculture for decades.
On a used example with a hot-bulb engine, check the condition of the hot bulb and pre-chamber, compression, the cooling-water circuit and crankshaft bearings of the long-stroke single cylinder, and the clutch and gearbox; given the age of this series, original parts are scarce and repair work mostly lies in the hands of Lanz Bulldog specialists and vintage-vehicle clubs.
Sources: SpecCodex register, model data: Heinrich Lanz HN 3
Technical data
Engine
| Fuel | Vielstoffcorrect |
|---|---|
| Power | 25 hp (18.3 kW)correct |
| Rated speed | 760/850 rpmcorrect |
| Cylinders | 1correct |
| Displacement | 4,767 cm³correct |
| Bore | 170 mmcorrect |
| Stroke | 210 mmcorrect |
| Injection pressure | 80 barcorrect |
| Cooling | water-cooledcorrect |
Dimensions and weights
| Length | 2,935 mmcorrect |
|---|---|
| Width | 1,700 mmcorrect |
| Height | 1,785 mmcorrect |
| Wheelbase | 1,645 mmcorrect |
| Ground clearance | 245 mmcorrect |
| Unladen weight | 3,050 kgcorrect |
Drivetrain and chassis
| Drive | rear-wheel drivecorrect |
|---|---|
| Gearbox | 6V/2Rcorrect |
| Front tyres | 7.00-20correct |
| Rear tyres | 10.50-24correct |
| Top speed | 20 km/hcorrect |
Origin and approval
| Construction | unit construction (no separate frame)correct |
|---|---|
| Units built | 181correct |
Where this model stands
Power-to-weight ratio: 6 kW/t (18 kW / 3 t)
Power class: Compact (< 40 hp)
Stronger than 12% of the tractors in the register — out of 15,663 models with a stated power figure.
Calculated from the documented figures above — not a rating.
Frequently asked questions
How much power does the Heinrich Lanz D 7531 have?
The Heinrich Lanz D 7531 delivers 25 hp.
How much does the Heinrich Lanz D 7531 weigh?
The unladen weight is 3,050 kg.
What engine does the Heinrich Lanz D 7531 have?
1 cylinders, 4,767 cm³ displacement, Vielstoff.
How fast does the Heinrich Lanz D 7531 go?
Top speed is 20 km/h.
What are the dimensions of the Heinrich Lanz D 7531?
2,935 mm × 1,700 mm × 1,785 mm.
When was the Heinrich Lanz D 7531 built?
Production years: 1935–1941.
What to check before buying
- Check the hour meter against the service records — a replaced instrument is the most common gap.
- Compare the data plate and chassis number with the papers.
- Check the weights in the papers against the figures here — attachments change them.
- Check front and rear tyre sizes: mismatched pairs strain the drivetrain.
- Shift the gearbox cold and warm — jumps only show up at temperature.
- Load the hydraulics and watch for sag.
- Ask about parts availability for this build year — the running costs hang on it.
A general list for this type of machine — no substitute for an inspection or an appraiser.
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This page carries 23 individual figures for this model. They come from 1 recorded source; every figure can be traced there. What we cannot document is not here — we leave gaps open rather than estimate them.
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Other models in this series
Sources: [1]
Tractor in 3D section
Turn the model, look inside and click an assembly — each one is explained.
