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Parts 28 & 29: Contrate Wheels

The term 'contrate wheel' is a fairly unusual synonym for what is more often known as a crown wheel (because its appearance is similar to a crown).  For the first few years, Hornby referred to this as a "contrite wheel" (sic), but at least that was corrected.  The word 'contrate' is probably only still used today because of its inclusion in the Meccano system.

28	Contrate wheel, 1½'' 50t	1902	-	3	2	2	N°8
29	Contrate wheel, ¾'' 25t	1902	-	4	2	2	N°8

The parts

Two very early parts in the Meccano system, designed to transmit drive when the axles are at 90 degrees.  Later on, bevel gears were introduced to do the job better, but contrates were by that time stamped out from sheet brass and thus much cheaper to make.  Although they were only included in outfits from 8 upwards in the 1937-on sets, they were included in the Gears outfit and thus are very common parts.

They are also used as clutches, since a pair of equal size mesh perfectly and only take a fraction of a revolution to do so (unlike the dog clutch, which can take up to half a revolution).  The 50-tooth part 28 also meshes perfectly with a 50-tooth gear part 27.  Since the large contrate is a common part with 8 holes it is often used as the crown wheel on a differential, and the smaller contrates used inside the differential instead of bevels.  Sadly, part 28 was never made with six holes and therefore cannot be easily used to make a spur differential.

Chronological variations

The first contrate wheels were milled from solid brass, before the invention of the patent boss in 1911. The photo to the right of three different solid small contrate wheels shows the variation in size of these early contrates.

With the introduction of the plastic gears in 1979, the same variations are seen with the boss as happen with the spur and pinion gears parts 26 and 27.  Initial UK-produced parts have a slightly longer boss than the later ones.  Parts marked Meccano England have a long boss, but some are known with a shorter boss.  These may have been parts manufactured in France in the early 80's.  Later French parts (with the stamping just Meccano) have shorter bosses, as do the 1990's versions in black.

Variations and oddities

Here's a strange duck – a nickel-plated contrate.  The stamping appears to be late pre-war (about mid-30's), but it is nickel plated as you can see by the brass one next to it.  The tappings are brass internally, showing that it appears to have been nickel plated before it was tapped.  Perhaps it was dropped in the nickel tank by mistake, says Michael Conduit?

Richard Payn (and others on Spanner) describe a way of reversing the boss on the plastic contrate wheels.  One way of doing this using common Meccano parts is shown to the left.  A long bolt is placed through the boss of the contrate, and on the other side a pair of double brackets and a large washer complete the "boss puller".

Tighten the nut slowly and the boss will come out cleanly.  You can then press it in the other side, as shown on the example to the right.  This is a very useful space-saving part, and might even pass as "genuine Meccano" depending upon how strictly you interpret the rules!

Dealer spare parts boxes

Individual part numbers

Part numbers for the parts on this page are as follows:    Unique part numbers
For identification, each variation has been given a suffix to the main Meccano part number. These suffixes consist of a two-character code for the colour, and if there are many variations, a further number and sometimes letter code to identify each variation. See the bottom of the 'Parts' page for further details.

You don't need to worry what the codes are, just click on any one for a photograph.

The button above turns on and off the display of DMS numbers (where they are known). The DMS (Development of the Meccano System, Hauton and Hindemarsh) published in 1972 and added to in 75 and 82, suggested part numbers for every variation of every Meccano part. These numbers aren't perfect, but they are recognised and also referenced in the EMP (Encyclopedia of Meccano Parts, Don Blakeborough).

Description	from	28	29
Milled from solid brass, squared profile, feather key	02	.mm	.mm
Milled from solid brass, squared profile, feather and tongue key	07	.mm1	.mm1
Milled from solid brass, squared profile, tongue key	07	.mm2	.mm2
Milled from solid brass, squared profile, tongue key, wide teeth	??	.mm2a
Stamped out with square profile, 1911 boss, tongue key	??	.mm2b
Brass with rounded profile, patent boss, tongue key	11	.mm3	.mm3
Brass with rounded profile, deep flange, 1911 boss, single-tapped	12	.br4
Brass with rounded profile, patent boss single-tapped	12	.br1	.br1
Brass with two holes, patent boss single-tapped	??	.br1a
Brass with eight holes, patent boss single-tapped	??	.br1b
Brass with standard boss, single-tapped	21	.br2	.br2
Brass with standard boss, double-tapped	28	.br3	.br3
Brass, post-war stamped, double-tapped	45	.br	.br
Yellow plastic, marked Meccano England, long brass pummel	79	.ye
Yellow plastic, marked Meccano England, short brass pummel	79	.ye2
Yellow plastic, marked Meccano and bar, brass pummel	??	.ye1
Black plastic, brass pummel	93	.bk
		ALL	ALL

Please send us pictures of missing parts! Hints and tips for pictures
Take a picture of the part in very good light, preferably on a plain yellow background, without a flash but with a tripod.
Ideally, trim the picture to about 150 pixels per inch of the Meccano part (unless the part is particularly big or small), save it as a reasonably good quality jpg file with a filename of exactly the part number, for example 19b.ni1.jpg, and email it to us by clicking on 'Contact us' at the top of the page. Thanks!

• A greyed-out box shows that no part exists for that colour combination.
• Part number codes with a green background have an attached picture of the part, just click once on the code to show a photograph of that part in a separate window.
• Parts marked "†" were temporary or economy parts, or existed only within specific themed outfits. The previous part continued throughout or afterwards.

Further information

Michael Clark      (at 2:54am, Tue 31st May, 11)

Picked up 4 28's recently, 3 UK and 1 French and noticed the French 28 has a higher wall height on the circumference and tighter radius giving a flatter bottom to the gear. Cheers Michael

James Dell      (at 1:39am, Sun 30th Jan, 11)

I recently purchased on ebay a contrate gear from the UK. After close examination I find its stamped meccano (x2) and Paris. Is this genuine? Reply: It certainly sounds like it, a genuine Meccano France part. Many were stamped Paris, very early ones and most later parts were stamped Meccano France.

russell hiscock      (at 6:52am, Thu 11th Jun, 09)

i also have a nickel part 28, mine is single tapped and stamped meccano x3. i'll send a photo when i put my hand on it.

michael conduit      (at 2:47pm, Sun 20th Jul, 08)

I have a post war part 28 which is silver coloured so probably nickel plated. The double tappings are brass so the plating was done before the threads were cut and are likely original. Reply: Thanks, a picture would be nice? And apologies for the over-zealous comment editor having a problem with the word "brass"!!!

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