Atlas based Domiracer.

This is my Atlas which I bought a couple of years ago. It came back from the US in a bit of a state. As I have a very original 650ss I decided to build this as a Domiracer style bike, so first off I did a rough build adding brackets & parts to get it up & running. Once I was happy that I wouldn't need to weld any more bracketry I stripped it down for the shiney shiney treatment. As I have always loved the look of the Francis Beart racers I opted for Ludlow green cycle parts, which combined with the polished ally tanks looks rather nice.
The engine has a Maney crank & barrels, JS super light rods & HC pistons, & a PW3 cam. I have a stage 1 Maney head which I may or may not fit, undecided on that, & may just fit the Atlas head as I feel it will give better performance for road use. The gearbox has a RGM CR gear set which works well on a light weight solo bike. When I have a bit more cash to hand I'll give Maxton a call to sort the suspension.
More pics to follow when it's a little more together.

I am intrigued by your rear wheel hub. Where did you source it? Is a cush drive included?

- Knut

That looks really great, I love the choice of colour.
And your nice engineering touches.
Hope you‘re fitting a sprint type tank rather then the full Manx bowser ??

mdt-son said:

I am intrigued by your rear wheel hub. Where did you source it? Is a cush drive included?

- Knut

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The rear hub is an old T140 front hub which I turned up a centre spacer for, as on a T160. The cush drive was originally designed by Mr Maney to suit the above hub, but are now made by Minnovation. The disc is for a 125 Jap bike, forget which, on a home made carrier. The caliper is a Taiwanese billet job also on my own make of carrier.

Fast Eddie said:

That looks really great, I love the choice of colour.
And your nice engineering touches.
Hope your fitting a sprint type tank rather then the full Manx bowser ??

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Thanks Nigel. As for the tank, I have a sprint type, but ironically wish I'd chosen the five gallon Manx type.

Matchless said:

Thanks Nigel. As for the tank, I have a sprint type, but ironically wish I'd chosen the five gallon Manx type.

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No!
Your subconscious knew what it was doing when you chose the sprint tank !!

Just waiting for the number plate to arrive from Tippers then I'll take it out for a run. I may fit a Manx type cowl at some future point.

Very nice !

Would definitely be enhanced by cowl / fly screen IMHO.

LOVERLY Bike, I mean really nice, should be a blast to ride! Thx for posting Cj

It looks as though you have the motor well forward - that is good. With that frame, you probably need 19 inch wheels. Tyres are always a problem. With 18 inch wheels and the motor well forward, the handling can be heavy. 19 inch make the bike more nimble.

I was silly. A few years ago I was in a friend's shop. He imported bikes from America. There was a very original Featherbed ES2 there, and it was not expensive. If I had thought about it, that bike would have been very nice if it had a 750 Commando engine, without changing anything else. When you build a cafe racer, most people would suspect what it can do.

Al its just the standard engine mounts for the Atlas Slimeline frame by the looks of things.
Matchless the bike is looking great and the frame colour is nice, better than an everyday black frame, I might have to start back on my 1960 Manxman cafe build, its been waiting way too long.

Ashley

Yes, the engine is where Norton put it originally. I do agree regarding 19" wheels though, & don't know why people fit 120 or 130 x 18" size tyres to featherbed bikes.

Matchless said:

Yes, the engine is where Norton put it originally. I do agree regarding 19" wheels though, & don't know why people fit 120 or 130 x 18" size tyres to featherbed bikes.

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On public roads, the effect of less trail is probably not very noticable. I fitted 18 inch wheels to my Triton to get better tyres. My cornering speed was the same. but I used to get off the bike after a race feeling exhausted. It was one of the reasons I sold the bike and built the Seeley. When I had 19 inch wheels on the Triton, it was light and nimble.
I could not get decent lap times when my motor was that inch further back, with 19 inch wheels. But the combination of the motor forward with 18 inch wheels was horrible. A manx frame with 19 inch wheels has about as much trail as you can get with that steering rake. The replica Manx Nortons in Australia handle like Suzukis. I don't believe they are as good as the original. With Suzuki type handling, grabbing a handful of throttle when you are halfway through a corner, is probably not wise. A manx just becomes more vertical and accelerates.
If you know anyone who has an original Manx - pay to have a ride on it. I was most impressed with the 1961 model 500 which I rode.
Your build should be a very pleasant ride, however you might check which wheel size was used with the Atlas and 650 SS.
I think the original Domiracer might have had 19 inch wheels and the motor a bit further forward.

Matchless said:

don't know why people fit 120 or 130 x 18" size tyres to featherbed bikes.

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Terrible pavement. A bit more contact patch is welcome in my neck of the woods.

Wheel diameter of a 18" x 120 is the same as the 19" x 4", so the trail remains the same, so steering remains more or less the same (slightly slower, but that's ok too with terrible pavement). It's all what you're looking for. Ain't no wrong, ain't no right.

Beautiful bike! Modern and realistic braking distance is always a welcome sight. As similar a concession to reality as tire width can be.

acotrel said:

A manx frame with 19 inch wheels has about as much trail as you can get with that steering rake.

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This assertion is wrong... again. More offset = less trail for the same steering rake angle. Roadholder yokes have a lot of offset, thus low trail (for the same rake angle), resulting in very responsive steering. Remember, Al, the two lines cross below the axle.

Preferences are one thing, but basic math is basic math.

t ingermanson said:

Terrible pavement. A bit more contact patch is welcome in my neck of the woods.

Wheel diameter of a 18" x 120 is the same as the 19" x 4", so the trail remains the same, so steering remains more or less the same (slightly slower, but that's ok too with terrible pavement). It's all what you're looking for. Ain't no wrong, ain't no right.

Beautiful bike! Modern and realistic braking distance is always a welcome sight. As similar a concession to reality as tire width can be.


This assertion is wrong... again. More offset = less trail for the same steering rake angle. Roadholder yokes have a lot of offset, thus low trail (for the same rake angle), resulting in very responsive steering. Remember, Al, the two lines cross below the axle.

Preferences are one thing, but basic math is basic math.

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I understand what you're saying regarding bad road surfaces, as some of the roads here in Cumbria, & indeed the rest of this run down country are appalling. Maybe I'll fit some wheels & tyres from an Electroglide.

t ingermanson said:

Terrible pavement. A bit more contact patch is welcome in my neck of the woods.

Wheel diameter of a 18" x 120 is the same as the 19" x 4", so the trail remains the same, so steering remains more or less the same (slightly slower, but that's ok too with terrible pavement). It's all what you're looking for. Ain't no wrong, ain't no right.

Beautiful bike! Modern and realistic braking distance is always a welcome sight. As similar a concession to reality as tire width can be.


This assertion is wrong... again. More offset = less trail for the same steering rake angle. Roadholder yokes have a lot of offset, thus low trail (for the same rake angle), resulting in very responsive steering. Remember, Al, the two lines cross below the axle.

Preferences are one thing, but basic math is basic math.

Click to expand...

t ingermanson said:

Terrible pavement. A bit more contact patch is welcome in my neck of the woods.

Wheel diameter of a 18" x 120 is the same as the 19" x 4", so the trail remains the same, so steering remains more or less the same (slightly slower, but that's ok too with terrible pavement). It's all what you're looking for. Ain't no wrong, ain't no right.

Beautiful bike! Modern and realistic braking distance is always a welcome sight. As similar a concession to reality as tire width can be.


This assertion is wrong... again. More offset = less trail for the same steering rake angle. Roadholder yokes have a lot of offset, thus low trail (for the same rake angle), resulting in very responsive steering. Remember, Al, the two lines cross below the axle.

Preferences are one thing, but basic math is basic math.

Click to expand...

I thought the yokes for the featherbed had 2 and a quarter inch offset. The yokes I removed from my Seeley had 65mm offset, and the replacements had 53mm. With the yokes on a featherbed, the bottom yoke limits how much the offset can be reduced. What limits the manx from getting even more trail is the steep steering head angle. The Manx is the only bike I have ridden other than my Seeley, which oversteers if you gas it when on a lean. And that is important. It is almost impossible to lean an original Manx as far as you can lean a 60s two-stroke. A Manx can out-corner any two-stroke, but it is not fast enough down the straights. The Manx steering geometry and torque are excellent, they just do not have the top end power.

Fat tyres arrived with two strokes. If you cannot get enough heat into the tyres, you get less grip. I see guys with classic bikes using tyre warmers before racing. I think they are kidding themselves. In corners, because of it's steering geometry, my bike stays more upright. I can enter any corner and accelerate full blast all the way through it, as long as I brake just before the corner. If the back does not go down just after I enter the corner, I am likely to run wide. All bikes do the same thing,most to a lesser degree. You will find that if you enter a corner too hot, you are likely to run wide. And when that happens, you need to lose speed, but there is a point in the corner where you must stress the tyres and accelerate. As the front of the bike comes up, the bike usually steers in the correct direction. It is not rocket science.
If you need to countersteer to enter corners, you have a problem. Insufficient trail causes the bike to understeer everywhere.
Road bikes are built to be more stable.

When I ride, I never worry about lap times. The harder you try to go faster, the slower you will go. I always work up to race speed slowly. I know where I can accelerate extremely hard. My Seeley is much easier ride than most other bikes. I learned to race by crashing. My wife does not know that, so she worries when there is no need.
If you have 3 rides at a race meeting, after 2 you should be fast enough for the last one.
If you ride around a race track trying to be faster on each small section. the total effect is not what you would expect. It is better to be smoother and work up to speed progessively and do the whole thing at higher average speed, even though you might be slower than others at certain parts of the circuit You will be less tyre-dependent.

My wideline featherbed racer had 18" rims in order to use the latest Dunlop KR124 racing tyres, 3.25 front 3.5 rear. The excellent Marzocchi/Grimeca front end came from my Ducati desmo single and was very very light. I had to drop the forks down a bit in the yolks and lower the frame mounting lugs for the rear spring/damper units about 1" to get back the ground clearance lost by the smaller wheels. I never thought about about rake or trail and always had a Kawasaki hydraulic steering damp[er on the stiffest setting.
The bike was neutral during cornering and would stay on course with hands off but the only way to get it to change direction was by a quick application of opposite lock. Shifting body weight or putting weight on one footrest had no effect whatsoever. I could approach a bend too fast in order to pass someone and rely on the tyre side load scrubbing off excess speed on entry to the bend. I measured the bikes max cornering lean angle at 58 deg. by putting a board against the ground contact points on the frame (grounding on the boss below the gearbox), footrests, brake pedal, gear lever and fairing.
My approach to cornering was : I've got the best handling bike and the best tyres therefore, however fast the bike in front is cornering, I can go faster. The only time I had problems with that was at Brands. I had easily dispatched a Rob North Triumph F750 replica and the only one left in front was a rapid Sealey Commando. I definitely met my match with that one and settled for second.
Big tyres and heavy brakes/forks definitely didn't work on my featherbed.