Mantis engineering Commando

Hi

I found a gallery of really nice photos of old race bikes & in amongst them I found the Mantis Engineering Commando. It was used in hillclimbs in Jersey. A caption states 11 seconds quarters no problem. Wow, if that's correct. Someone has posted "Malcolms steed still going strong then, at one stage I think it was the fastest bike up Bouley Bay,"
Its the back end of the bike that is fascinating. Triangulated swinging arm twin shock. 900cc engine. Does anyone know more?

Cant down load a photo cos its on fliker.

link is http://www.flickr.com/photos/michael_be ... 310065221/

all the best Chris

Hi Ikren

& thanks. Cant use a photo on fliker without asking !

Forgot to say, what has been done to the timing cover? Points cover for ignition etc but? not sure why the centre has been built up or what the plate is?

Chris

Chris said:

Hi Ikren

& thanks. Cant use a photo on fliker without asking !

Forgot to say, what has been done to the timing cover? Points cover for ignition etc but? not sure why the centre has been built up or what the plate is?

Chris

Click to expand...

Crank fired ignition?

Too high to be centred on the crank.
Maybe on the half-time pinion. (?).

That sure is an elaborate braced tubular swingarm.
Shock angle wouldn't allow much movement.. ?
Neat bike.

Really like the underslung oil tank, and logical battery position. Waaaaay back in 1966/67 I drew up a virtually identical set up for my BSA Gold Star. However I chickened out of making it, because I wasn't confident about maintaining the oil supply to the oil pump.
Very nicely sorted out motorcycle, I love the lean look but the swinging arm looks a bit too complex to me.
cheers
wakeup

Dual Ignition timing cover ? :?

This lighter one was on google images:

I just came across this post whilst browsing around the web - I live in Jersey and know a bit about this bike ............

It was built around the early/mid 70's I believe and a friend of mine has owned it for many years. It was initially built and used for circuit racing but then the owner used to race it in local 1/4 mile sprints and hill climb events with a good degree of success - he held the local outright sprint record for bikes for many years at about 11.434 seconds - a number I remember well as I was constantly trying to better it in the late 80's on what should have been much faster japanese machinery !

One phrase that was often used to describe the bike was that it was 'the beast that breathed through it's bones' - the frame was actually in two sections and used the engine as a stressed section - the rear part of the frame bolted to the rear of the cylinder head and the carbs fed the motor through the frame - hence the description.

These photos were taken in 2001













I don't know a lot about the technical spec of the motor but I do know it went very well - having grown up admiring the bike from the age of about 10 in the mid 70's I was very fortunate and honoured when the owner offered me the chance to ride it at our local sprint. As you might expect on an unfamiliar and borrowed bike with the gear change on the 'wrong' side for me no records were going to be set. But I can say that I've not ridden many other bikes that launched away from the start line as swiftly as this one !

I'm just sorry that I cannot track down any video - you didn't just listen to this bike, you felt it as well. I'll ask around and see if I can track anything down for you all.

Thanks for posting these photos and supplying the history.

Cool bike.

Must be some serious re-construction inside that timing cover! It´s cut open in the front, can´t see any drive chain for the cam? Sprockets? Would love to see the cover come off.... Is the ignition really set on the half-time pinion? Looks a bit too far to the rear... What are those carbs, Lectrons? Or where they all flatslides?
Tommy

It must be the only Commando that won't wet sump.

Interesting bike for period, nice to know more about it!

That sure is an elaborate braced tubular swingarm.
Shock angle wouldn't allow much movement.. ?

Rohan the shock angle would increase the movement would it not, it would have also required heavier springs to compensate ie the moment angle has been reduced and the hypotenuse has been increased in length therefore increasing the travel at the wheel axle, or have I missed something?

Burgs

carbs are MK2 Amals. I, too, would like to look inside the timing cover. very clever stuff.

The engine cannot wetsump as the oiltank is below the engine. There should still be a chain inside the cover to drive the cam. There was a plate welded into the timing cover to separate the new ignition from the oil. Mantis obviously was aware that the ignition on the cam end will give variable timing due to the chain drive. So he put it on the half time wheel - very clever.

Hartmut

I could sit and look at pictures of that frame for hours. Words like 'innovative' and 'out of the box thinking' are often over used these days, but they surely apply here!

For example, I'm pretty sure I have never seen inlet manifolds used as a structural part of frame design before!

It does make me wonder though, did the designer think things through fully re his impact on the exisiting design aspects? He has put a lot of load onto fixings and castings that were never intended to take it. I know nothing of the bikes history though, which may well speak for itself.

Thanks again for the extra pics of this most interesting bike! I agree that it seems odd to see the front half of the frame bolted to the head with what was originally only three 5/16" bolts, however, it must be remembered that the whole rear end of a Formula One car of the period was only held in place by four 1/4" bolts! Like the others, I'd love to know more about the engine, and would also appreciate some photos of the swing arm area (I agree about the improved shock travel comments - lay-down gives a better performance if the dampers are of a high enough quality) and the gear lever mounting.

He has put a lot of load onto fixings and castings that were never intended to take it.

Click to expand...

Maybe that was the reason behind the move from short circuit to sprints etc, it had a much better chance of staying together long enough to get the win. Very impressed with all the work and actually doubt it had any reliability issues.

Hi Pebble 35

And thank you

The more of this bike I see the more fascinating I find it. It is also nice to know that the bike is still around.
How much frame/engine plates are there below & behind the engine?
If these are pretty good then the mounts for the head make more sence but I would love to see photos of the build of this bike.
Never been near those times with my Commando sprinter very impressive.

Keep em coming.

Chris

Ah.......... The old using the frame backbone as the intake manifold trick.