Featherbed: Twin vs Manx, handling, weight, etc

Fast Eddie

Fast Eddie

VIP MEMBER
Joined
Oct 4, 2013
Messages
21,596
Country flag
Inspired by the chat elsewhere about Rudi Thalhammer’s Domiracer, I did a bit of reading up on the Domiracers.

I confess, I was somewhat ignorant. I hadn‘t realised they were as good as they were.

In particular the commentators of the day noted the lighter overall weight of the engine, even without alloy barrels and use of exotic alloys for cases, and the lower centre of gravity. Both of these factors giving handling benefits.

I had always believed the twin could not sit low enough in the frame so has a higher COG. But, although it may sit higher, the lack of overhead cam box etc did give it an overall lower COG. Apparently.

Whilst it’s very interesting to read, has anyone ridden a Manx framed twin and a full Manx, and if so could you share your thoughts and comparisons please ?
 
Seeley920 said:
Don't forget, the Domiracer (Lowboy) was a different frame, specially built to accommodate twins so the engine could sit lower
Click to expand...
Yes, I realise that, but I was reading the comments about the early versions, which used Manx frames.

I can only assume the later lowboys were even better.
 
Only ridden a slimline 99 (a lot), a wideline ES2 and a Manx. Sorry, not enough good rider to feel any great difference. Except of course the weight difference. Maybe a little quicker turn in on the Manx. Brakes of course differs.
 
Fast Eddie said:
Inspired by the chat elsewhere about Rudi Thalhammer’s Domiracer, I did a bit of reading up on the Domiracers.

I confess, I was somewhat ignorant. I hadn‘t realised they were as good as they were.

In particular the commentators of the day noted the lighter overall weight of the engine, even without alloy barrels and use of exotic alloys for cases, and the lower centre of gravity. Both of these factors giving handling benefits.

I had always believed the twin could not sit low enough in the frame so has a higher COG. But, although it may sit higher, the lack of overhead cam box etc did give it an overall lower COG. Apparently.

Whilst it’s very interesting to read, has anyone ridden a Manx framed twin and a full Manx, and if so could you share your thoughts and comparisons please ?
Click to expand...
FYI the works 500 Domiracer built by Doug Helne and ridden by Top Phillips to third place in the 1961 IOM TT did have alloy barrels.
 
Hi FE
First Norton was a 99, then fitted a 59 Bonneville engine, then fitted a unit construction triumph engine, then bought the Manx in 71, rode it on the road a couple of years then fitted another Triumph engine.
Restored the Manx in the late 80s, my thoughts now are a bit blurred but now having a 650ss to compare to Manx I do reckon the Manx is an easy bike to ride fast on, that could be a few things though, better tyres, much better brakes, feels much lighter, is faster so long as you are in the correct rev range.

Thing is they all handle well, guess history speaks for the Manx being a better bike as a race winner though, so sorry I can't help you that much, the Domiracer may have been a better bike, but too little too late.

Burgs
 
Burgs said:
Hi FE
First Norton was a 99, then fitted a 59 Bonneville engine, then fitted a unit construction triumph engine, then bought the Manx in 71, rode it on the road a couple of years then fitted another Triumph engine.
Restored the Manx in the late 80s, my thoughts now are a bit blurred but now having a 650ss to compare to Manx I do reckon the Manx is an easy bike to ride fast on, that could be a few things though, better tyres, much better brakes, feels much lighter, is faster so long as you are in the correct rev range.

Thing is they all handle well, guess history speaks for the Manx being a better bike as a race winner though, so sorry I can't help you that much, the Domiracer may have been a better bike, but too little too late.

Burgs
Click to expand...
The Domiracer was being built as a replacement for the Manx, but that came to nought.
What is not generally known is that Phil Read was using the Domiracer in pratice for the TT but decided to race his own Manx in the race where he finnished 2nd, behind Hailwood on yet another Manx. He inherited the lead after Gary Hocking crashed the MV and decided to retire after visiting the pits.
 
Rumors also have it that the Domi limped over the line, after some major motor drama. The Manx was (is) known as reliable, the Domiracer project was not there yet. If the cam followers from the previous thread was any indicator, one can only expect a certain life expectancy before they turn into cam peelers. At 9000 rpm, that might only be 5 1/2 laps around the mountain!

The fact that a bungee cord holds the exhaust onto a works bike makes me love it that much more though.

Featherbed: Twin vs Manx, handling, weight, etc


Just a gentleman's amount of daylight under the front tire.

Featherbed: Twin vs Manx, handling, weight, etc


Never ridden a Manx, so can't help with your request, but one can only assume that a Manx rides best with the frame designed for it, and a Domi rides best with the Lowboy frame designed for it. The '61 TT was a culmination of the project, as well as the end. Norton had been sending 500cc twins to Daytona for over a decade since US race promoters made the Manx outside the race rules, so I doubt the Lowboy frame was being run in '61 on a hunch.

Now that Andover will be reproducing the Lowboy frame, might be worth a look. I'd love to find out more geometry details.
 
t ingermanson said:
Norton had been sending 500cc twins to Daytona for over a decade since US race promoters made the Manx outside the race rules, so I doubt the Lowboy frame was being run in '61 on a hunch.
Click to expand...

That’s a good point, the twin had indeed had a decade of US driven race interest behind it.

’cam peelers’… I like that one !
 
The Lowboy was all about reducing COG (of bike and rider) and reducing frontal area.

The Manx frame is as big as is dictated by the tall engine (big flywheels, long stroke, big head, tall cam box), the sump sits between the lower frame rails and the cam box sticks up between the top ones!

With the Lowboy they were taking advantage of the physically smaller engine.

And the fact that most pro racers were built like race horse jockeys …!

Personally, I love the look of the Lowboy, but I’ve tried one, and at a tad over 6ft I seem to have nowhere for my knees and elbows to go…
 
from what I have read, the Domi engine used was at the limit of reliability, with cylinder head components being some of the weak spots, and that was after substantial mods !
 
t ingermanson said:
Rumors also have it that the Domi limped over the line, after some major motor drama. The Manx was (is) known as reliable, the Domiracer project was not there yet. If the cam followers from the previous thread was any indicator, one can only expect a certain life expectancy before they turn into cam peelers. At 9000 rpm, that might only be 5 1/2 laps around the mountain!

The fact that a bungee cord holds the exhaust onto a works bike makes me love it that much more though.

View attachment 82955

Just a gentleman's amount of daylight under the front tire.

View attachment 82956

Never ridden a Manx, so can't help with your request, but one can only assume that a Manx rides best with the frame designed for it, and a Domi rides best with the Lowboy frame designed for it. The '61 TT was a culmination of the project, as well as the end. Norton had been sending 500cc twins to Daytona for over a decade since US race promoters made the Manx outside the race rules, so I doubt the Lowboy frame was being run in '61 on a hunch.

Now that Andover will be reproducing the Lowboy frame, might be worth a look. I'd love to find out more geometry details.
Click to expand...
I didn't know Andover were going to produce a lowboy frame!
I have always liked the design of the frame and being 5ft 6" it could really suit me hmmmmmm
I was talking to a bloke around 10 years ago that raced one with a 5 speed box ,his secret weapon he called it
Brilliant bike
 
Fast Eddie said:
Personally, I love the look of the Lowboy, but I’ve tried one, and at a tad over 6ft I seem to have nowhere for my knees and elbows to go…
Click to expand...
Would it be worth exploring a "LongandLow" boy? The front of the seat is much further forward on the Lowboy. Featherbed length would give a bit more knee and elbow room, not to mention long carb inlets. I certainly don't have much of a jockey build either. The reason I never went pro. Wink, wink...

baz said:
I didn't know Andover were going to produce a lowboy frame!
Click to expand...

They announced they were going to do a limited amount of race frames this year based off an original frame they have in their possession:

Featherbed: Twin vs Manx, handling, weight, etc

The "cam box" dent is an interesting feature.

I've got a few motors I could imagine slipping in there.
 
t ingermanson said:
Would it be worth exploring a "LongandLow" boy? The front of the seat is much further forward on the Lowboy. Featherbed length would give a bit more knee and elbow room, not to mention long carb inlets. I certainly don't have much of a jockey build either. The reason I never went pro. Wink, wink...



They announced they were going to do a limited amount of race frames this year based off an original frame they have in their possession:

View attachment 82963
The "cam box" dent is an interesting feature.

I've got a few motors I could imagine slipping in there.
Click to expand...
...like a Commando with JS pistons etc!
 
t ingermanson said:
Would it be worth exploring a "LongandLow" boy? The front of the seat is much further forward on the Lowboy. Featherbed length would give a bit more knee and elbow room, not to mention long carb inlets. I certainly don't have much of a jockey build either. The reason I never went pro. Wink, wink...



They announced they were going to do a limited amount of race frames this year based off an original frame they have in their possession:

View attachment 82963
The "cam box" dent is an interesting feature.

I've got a few motors I could imagine slipping in there.
Click to expand...
It’s also the low seat height that would put me off, too little distance twixt seat and footrests.

I’ve kinda done playing around like that, I’ve played around with frames before, both with some success… and some cock ups !

So I’ve learnt through experience that I actually don’t know more about frame design than the rather clever chaps who laid down these designs originally… despite what I might think !

Plus, having seen just how fast a good Manx is through excellent handling, I wouldn’t want to mess.

So, I’m pretty set on the idea that the next thing I build will have a Manx chassis.

For now…
 
Just wrote to Andover to inquire about that frame. Wonder if there are any available, and how much they are going to cost. I'm also guessing the geometry of the width of the frame is similar to the width of a wideline Frame?
 
seanalex said:
Just wrote to Andover to inquire about that frame. Wonder if there are any available, and how much they are going to cost. I'm also guessing the geometry of the width of the frame is similar to the width of a wideline Frame?
Click to expand...
There are others making the Lowboy frame too. Dresda used to make them, I’d imagine they still do.
 
t ingermanson said:
JUST GET A MANX ALREADY!!! Any of the new short strokes will get you miles ahead of where you'll be starting with any other project.
Click to expand...
Yer think… I’d never thought of that… (I’m lying of course, I’ve obsessed over it in great detail) !

I‘d love a Manx. Just can’t decide which of the kids to sell first.

Personally, I have no interest in building a 500 twin Domiracer replica. But the cheaper alternative to a Manx that I am mulling over is a 920 twin Manx…

Obviously the 920 would have quite a lot more oomph. I believe the engines would way more or less the same. I had always assumed a twin would upset the COG and spoil the fine handling of a proper Manx. But having read through some of the recent Domiracer stuff I’m not so sure.

Trouble is I am yet to meet someone who owns / has owned a good Manx who doesn’t think it’s the finest thing on two wheels…!
 
Back
Top