Commando motor in solid frame

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acotrel said:
When you race with a drum brake, the distance you can safely brake up to a corner is usually less than with a disc brake.
Click to expand...

You probably mean more, when you say less.

The rest is your impressions and opinion, stated as though they were fact.
 
Sorry - when I brake up to a corner, I usually do it progressively closer to the apex lap after lap until I can just get around without crashing. So I tend to think in terms to the distance into the corner getting greater from my initial braking point. The later you can brake, the better and the earlier you can get back onto the gas, the better. Drum brakes limit how far you can brake into the corner because they don't stop as well or as reliably as discs - so you always have to leave room to do some antics. The cute thing about drum brakes is the way they fade. You can set the up to get progressively stronger, but then you have to get them hot enough to work. Disc brakes don't seem to change much once you've got the appropriate linings in them to suit your circuits. It's a much easier deal.
 
acotrel I have constantly heard you slagging off drum brakes on this forum yet by your own admission you appear to NEVER had your drum brakes professionally relined ever :!:
you sound like Fast Eddie and I quote, “Apart from minor lockups when using AM4 linings without a proper warmup, the only proper drum brake lock up I ever suffered was when the cam went 'over centre' and locked up the brake. This only occurred cos I was too tight / skint and had run the shoes past their minimum thickness, allowing the over centre situation to occur.”

I have had motorcycle drum brake relined by Joe Dunphy at least 3 times when I was living in greater London, with skimmed brake drum, the statement about warming up green front brake linings is true, but they were the equivalent of disc brakes at that time (or better if you let the professional cast his/her magic on them beforehand)
There is no excuse for you not to try it and get this on your bucker list before you kick the bucket (joke :!: :) ) and stop slagging the humble drum brake off :!:
 
Something else to consider is what tyres/tires Alan was using in all these sagas. ?

Something I heard a good while back may have some bearing on this.
A work colleague mentioned he had had new XXXXXXX tires fitted, by the importer, who said "try these".
(This is a road bike.) Owner said these tyres were like nothing he had ever seen, "you could lean the bike over until it was 90 degrees off vertical, and they still hung on". (bit of an exaggeration, but you get the picture.)

Apparently they were proddy racing specials = a really sticky compound.
Nothing on the sidewalls to indicate they were different, in the slightest.

Said they were a bit of a waste on a road bike, and they only lasted about 3000 km.
But were fun while they lasted.
There are tyres, and there are tyres ?
 
jim s chimes in with a few utterances and wants to talk about "Commando motor in solid frame"

next thing you know filibusterer rohan takes over lol

don't like it? toooo bad

[video]https://www.youtube.com/watch?v=6sJqTDaOrTg[/video]
 
Don't panic, don't panic, don't panic.
Take your meds, and take a deep breath.
All will be well.

And Alan HAS his motor solidly mounted.
And likes to diverge, a little.
Or we'd have x10,000 more posts, on trivial variations thereof....
 
I was brought up racing on bad tyres. These days when it rains I'm in with a big chance of winning. The young guys are have become reliant on good tyres. If you lock a drum brake in the dry, good tyres mean you have less chance of losing the front end. However when it rains, you are back to the good old days.
Are we talking about commando engines in solid frames in general or in specifics ? If you are building a bike, why wouldn't you make it as safe as you can ? As I've said previously many times a good bike is not the sum of it's component parts, it is about the total package - the way the bits interact.
If you build a featherbed commando with the motor too far back, with a drum brake - you might be creating a hazard, if it is vague in fast corners and you need to back off quickly. Fortunately most commando motors lean forward in featherbed frames - that helps.
 
acotrel said:
Fortunately most commando motors lean forward in featherbed frames - that helps.
Click to expand...

Be interesting to compare a laid-forward commando-in-featherbed with an upright commando-in-featherbed then, wouldn't it. ??

You could probably get the UPRIGHT engine further forward, to get more weight on the front wheels.
If that is whats needed.

Weight distribution on the front and back wheels used to be a statistic they included in the specs chart.
Anyone noted this lately on such bikes, you NEVER see them quoted anymore.
 
My understanding is that a Commando engine sits too high in a featherbed frame. The engine is wider than the single that the frame was designed for and can't fit between the lower frame rails.

I rode a Matchless G80 in a featherbed and it was considerably better steering than my Commando/featherbed bike. It just turned into corners much better.
 
Interesting.
You didn't happen to put a set of kitchen/bathroom scales under the front and back wheels ?
 
Rohan said:
Interesting.
You didn't happen to put a set of kitchen/bathroom scales under the front and back wheels ?
Click to expand...



:) I could do it for my bike which is downstairs. Before I put lights etc on it , it was 330lb ready to race.
 
Be careful - we don't want to hear you had a huge crash attempting this. !
I've heard of this happening....
 
Rohan said:
Be careful - we don't want to hear you had a huge crash attempting this. !
I've heard of this happening....
Click to expand...


I'll be careful. I intend to measure the rear wheel weight by pulling a wheelie over a weighbridge and then doing a stoppie to measure the front wheel weight. I can't see what could go wrong.
 
OK, using bathroom scales Front 176 lb, rear 178 lb.

I didn't bother chocking the wheels to match the height of the scales so there might be a slight inaccuracy, but for comparison of front to rear it should be OK.


As you can see from the pic, the motor is inclined forward but maybe there's some space for it to move forward a bit.

Commando motor in solid frame
 
Hey Dances , I need to do this, what do you think the ideal balance should be with a standard Commando frame with an 850 motor?
I weigh 82 kg/s
Regards Mike
 
When I first started racing my short stroke Triton 500, it had dramatic power characteristics and it's handling felt vague in corners. I tamed the power characteristics by developing a 2 into 21 exhaust and I made a new set of engine plates to move the engine forward so the casting on the front of the motor touched the mounts on the down tubes on the featherbed frame. Only then did I start getting decent lap times and could ride with any level of confidence. Much later I rode a friend's 500cc Manx and found out the difference from a Triton - chalk and cheese. I was about 5 seconds a lap faster, yet about 5 MPH slower down the straights. I've found that with old British bikes, the more weight it has forward and down, the better. It is really pleasant to be able to ride extremely aggressively and not have the shit scared out of you. That Triton felt vague in corners and if you could not keep it on the boil at all times, it would do nasty things to you. I still don't like to even think about what racing was like when I had that bike. You might think I was an inadequate rider - NOT SO ! It turned me into an instant dud. My Seeley is a world apart from that.
Some people believe that if you put the best motor into the best frame, you would have the best bike. - Norvins are a load of crap - the weight distribution ends up at around 50 %. You'd need to be a real hero to ride one well on a tight circuit .
 
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