AEC Semi -Auto drive

Driven by my mate Tony Wallace he demonstrates the operation of Semi Auto gearbox on my rare Aec mammoth major, notice the Hi-Low split inbetween the changes.

[@jamesfrench7299]

I have heard of SCG in trucks but never seen one in operation. I presumed they were the electro pneumatic set up, never expected to see this large air changer, especially on an AEC Mammoth Major of all things. Never seen a splitter with a semi auto before either (but would expect it to exist). Wouldn't want to flat change this!! Fantastic upload. Sounds to be a 691.

[@ianpegge9967]

With that gear change head it would be a pneumatic only change. Normally of this vintage I would expect the switch on the top of the gear knob to control an electric two speed rear axle rather than a splitter. A lot if leyland leopard buses and coaches had this setup.

[@jaguarspeed56]

Memories when I used to drive one of these, great truck

[@markburgess4528]

I used to live in Hanwell just up the road from AEC. When I was young I wanted to be a engineer and work for them. Sadly they closed down before I left school. I remember stopping with my dad sometimes at weekends as they had a 'showroom' that always had one of their lorries in. I also remember seeing what must of been test vehicles driving in the area. Just a chassis with no bodywork on.

[@TomRelubbus]

This looks to have a pneumocyclic gearbox, as was fitted to Leyland Leopard coaches (of which I drove many). I also drove an AEC coach for a few years which had the epicyclic gearbox (much nicer), that also had the 760 engine that I'm guessing this Mammoth has. Love that ergomatic cab

[@octopus680]

Yes indeed Tom and yes 760 powered and ive always loved ergomatic cabs too.

[@robertsmith9810]

@@octopus680 i owned 8x4 tipper insulated alloy body T11 fuller 9 speed ergomatic cab 1978/79 i enjoyed driving the truck but the engine gave some trouble i remember one problem was it broke injector pipes and lost drive to fuel pump their i had a bit of luck as the local layland dealer workshop dealer had experienced this problem as it was caused by compressor housing cracking and causing the drive to the fuel pump to fail and i suppose vibrating the injector pipes to break what fun running trucks was BUT at least you could fix thing without the use of a computer as with euro 6 engine, at least being retired i have not got to mess about with EV trucks HOW do you recover a broken down EV vehicle i think you need a degree in science to run and service them

[@octopus680]

@@robertsmith9810 Sounds like the later type with the High Datum cab and Octopus model, normally bomb proof them.

[@DaveGreeneramblingcarpenter]

Never seen that gearbox, one of my favourite trucks, and the v8 D series ford's,

[@octopus680]

Thanks David and i hope you have seen the vids of my V8 d series on here.

[@DaveGreeneramblingcarpenter]

@@octopus680 ah thanks for the reply,, I did see your ford's as well, great looking, sounding lorries, fair play to you

[@octopus680]

@@DaveGreeneramblingcarpenter Cheers -Very kind.

[@northstar1950]

I didn't realise this was available on HGVs

[@robertp.wainman4094]

I'm sure the Leyland National bus took design cues from the Ergomatic cab......both well considered by industrial designers as they're attractive without appearing 'overstyled'.

[@robertsmith9810]

i used to own Leyland TL11 version fuller 9 speed for it`s many faults due mainly to engine it was one of my favourite Trucks and i suppose why i bought DAF`S later

[@octopus680]

it was the Perfect drive with a fuller box.

[@basiltaylor8910]

A very rare beast a 760 Ergo rigid eight with a 'Tower' Change Leyland Pattern Semi-Auto Box,as engineers at the Southall Music Academy offered their column mounted Coventry 'Self Changing Gears' semi-auto,like a Bristol RE bus. SCG Semi-auto options listed by AEC,s publicity department as 'Monocontrol'. The box has its quirks as one has to be wary of the splitter section engaging with out the driver knowing with resultant engine damage . What is she like to drive on steep twisty roads, 'Tower' Change boxes the ratios are too widely spaced, so the splitter will be hard worked, better off with a proper 'Range Change' set up.

[@stuarthowarth2972]

On Leyland Leopards with this set up, the operator could specify their preferred gearbox/rear Acle ratios

[@basiltaylor8910]

@@stuarthowarth2972 Yes ,I know Soudley Valley Coaches and Yelloways of Rochdale specified the 6-speed ZF 6-80 synchromesh manual gearbox on their late model Leopards, Back& White National Express opted for the 5-speed 'Tower' change pneumocyclic gearbox with a 2-speed Eaton drive head in the back axle. SMMT was unique as their Leopards were fitted with a close ratio 5-speed Self Changing Gears Electrocyclic box with column change ,like a Bristol RE.

[@seancooke7332]

Class just like our old Leyland Ulsterbuses in the 1970s . Leyland Leopards and Bristol REs. Same type of semi auto l think.

[@octopus680]

Yes it is Sean the same box mate.

[@davidjones8680]

Training up the agency driver I see. Looks like he's got it sussed.

[@octopus680]

He he you know Tony David

[@tonywallace7212]

HA

[@LawnMowersThingsThatMakeNoise]

is that the same gearbox thats used the leyland leopard/national etc etc where you wait a few seconds between gears ?

[@octopus680]

Yes thats bang on and yes it has to be a slow selection inbetween changes.

[@chrisg6086]

Funny to see the button and switch you'd normally see on the end of a column stalk on a Leyland - wouldn't they normally be horn button and dipswitch respectively? Surely it wasn't built with a horn button on top of the gear knob?? Sounds beautiful, though :)

[@octopus680]

Tony who was driving it was saying the same thing, i think it may have been the best switch to fit at the time..?

[@davidwebster3519]

I may very well be wrong in saying this, but I think that switch on the gear selector may be for splitting the gears. I heard of one of these in Australia that had a 10 speed semi auto but I never saw the gear selector on it but if this is a 10 speeder that would explain the switch. I'm more familiar with semi auto buses which are usually 4 or 5 speed and never saw a switch like this on their gear selectors. Like I say I could be talking a load of rubbish because I don't know for sure, just a bit of a guess.

[@chrisg6086]

@@davidwebster3519 yes it is, I was just commenting that it appears to be something else that has been re-purposed for that. Normally, there would be a similar switch on the gear knob for the splitter, as on the Two Pedal Beaver. I have an interior photo of the original fitment on an Atkinson with the same 10-speed box. As you say the bus chassis would be 4 or 5 speed

[@DecalCentralUK]

@@davidwebster3519 some semi auto Leyland Leopard coaches had this switch and it was for selecting high or low ratio on the back axle usually the Eaton 2 speed

[@basiltaylor8910]

No, barking up the wrong tree, the knob is for the 2-speed Eaton Drive Head in the back axle, an option on Leopards

[@tinychetty3067]

it looks like the Leyland OPS gear mechanism. I wonder if this was a bus chassis converted to a truck.

[@octopus680]

No Tiny its 100% lorry chassis and don't forget this is a eight wheeler.

[@chrisg6086]

It's a standard SCG component, and was also fitted to some semi-automatic Atkinsons

[@edwardkennedy9919]

Nice driving, never seen this type of transmission on a lorry which make of gearbox is it.

[@chrisg6086]

Self Changing Gears, a Leyland Motors subsidiary. Fitted for donkeys' years to things like the Leyland Leopard, Leyland Titan, the '2-Pedal Beaver', etc

[@carlnapp4412]

What kind of clutch works here?

[@octopus680]

Fluid flywheel -its semi -AUTOMATIC.

[@davidkelly5899]

Leyland bus system

[@octopus680]

Yes basically David.

[@onlyme8001]

That would be a Wilson gearbox. SGC where column mounted and electric change. That sounds air operated to me so a Wilson gearbox.

[@guyatkinson7442]

When I started as an apprentice truck mechanic 52 years ago at NMU transport York, they ran a few Leyland Beavers with that gearbox in the early 1970s, they were as you say Wilson/SCG boxes the early ones were only 5 speed and had the same splitter switch which operated an Eaton 2 speed axle, the later ones had the built in splitter, they were both troublesome as the drivers used to change gear too fast and one brake band was engaging before the previous gear had fully released I can still smell the burnt oil that used to come out of those gearboxes, As with all Leyland products of that era they brought out a modification that dumped the air quick and cured the problem but the damage was done the word was out and no one wanted to know those boxes

[@andypreston1524]

I bet a fair few of these were abused in their days with full power "Straight Through" gearchanges.......

[@octopus680]

They will take it as long as the gear change is slow...

[@robertp.wainman4094]

​@@octopus680 But when driven well can be beautifully smooth and relaxed. Many bus drivers certainly abused them....much to the passengers discomfort.