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Collection, Preservation and Display of Old Lawn Mowers

Ransomes Certes models

Here are some questions - I am looking for advice on when my Ransomes Certes were made.

Ignore the Ransomes Ajax Mk3, we're looking at the two nearest in the photo.

I recently got a hold of a couple of Ransomes Certes 16", both missing their labels.

Can anyone tell me their model numbers (eg Mk7) - Yes:  Junior is a Mark 10 (domed nut and smooth sides); No3 is a late Mk12 possibly post-1969?

Both had their labels on the gear cover, not on top of the gear casing between the grease nipples.

One ("Junior") is surely an ex-Overgreen since it has wheels, but I have only seen photographs with pram wheels, and mine are heavy wheelbarrow wheels.  Were the handles locally made or were they commercially available aftermarket items?  They have rubber grips.

The roller has the bramble pattern.


The other machine ("No3") has a normal Certes wooden transom type handle, but the handles themselves are four-piece with a bridge connector at the cross point.  The only ones I have seen in photographs had a welded cross point with the model name and mark on a badge attached to the gusset.  This one has a grooved roller.   Also, the gear cover is retained by a few screws on the perimeter, but the one with wheels ("Junior") seems to have just one domed nut near the middle.


Both machines have little arches on the underside of the side castings to locate the wheels axle when being transported.  Does that mean that both are ex-Overgreen, or did all Certes have the feature?
The Mark 12 parts list shows a pair of transport wheels so that means at least all late models had the feature.


I'll try to link some photographs here.

Additional - I can't use the same spanners on both Certes!

Right, I've removed some sample screws and measured them.

Junior cylinder adjuster (Maker SPARTS, grade not present / worn away)
Thread dia 10.95 mm x 14 tpi - closest is 7/16 BSW at 11.1125 mm dia.
Screw head hex 15.17 mm AF and locknut 18.18 mm AF (15 mm and 18 mm ring spanners fitted well but 15 mm open end a bit tight)

No3 cylinder adjuster (Maker AOTO (indistinct), grade S)
Thread dia 9.35 mm x 24 tpi - closest is 3/8 UNF at 9.525 mm dia.
Screw head hex is 14.20 mm AF and locknut 14.48 mm AF (9/16 combination spanner fits)

Junior handle fixing (upper screw) (Maker SPARTS, grade R)
 Thread dia 9.4mm x 20 tpi - closest is 3/8 BSF at 9.525 mm dia.
Screw head hex 15.26 mm AF and nut 15.28 mm AF (15 mm ring spanner a tight fit but open end too tight)

No3 handle fixing (upper screw) (Maker GKN, grade S)
 Thread dia 9.26 mm x 24 tpi - closest is 3/8 UNF at 9.525 mm dia.
Screw head hex is 14.16 mm AF and locknut 14.35 mm AF (9/16 combination spanner fits)

Conclusion - Junior is Whitworth and No3 is Unified.
When did production change?
Edit - the Mk 12 parts list shows the bolting to be Unified Fine, with the exception of BSW for the roller freewheel cover bolts and 2BA for the gear case cover screws and nut.

Edit - Mk12 was UNF as morked on the otherwise common tapped castings.  Older models were Whitworth.


David Bouchard Fri, 02/10/2015


sorry I only found your post tonight,

I now have Certes Mk 8, Mk 10 and Mk 12.

At least one of them needs to go, most likely the Mk 12 once it is refurbished to some extent - two new ball bearings, two new roller bushes, possible other parts - and smart new paintwork.  The cylinder and bottom blade have been reground, and the cylinder has been shot blasted and powder coated.


Edda Fri, 05/02/2016

Hi David

I have have not logged on for ages are you still looking to sell one of your Certes?




David Bouchard Tue, 22/03/2016

Hi Geoff,

like you I have not logged on for ages:

yes I cannot keep three Certes and two will have to go.

The Mk 8 and the Mk 12 will be sold when finished, and I will keep the Mk 10 because it has the transport wheels I need.