Topic: '73 500 - Subframe Fabrication

[Riceman]

I was somewhat shocked at how subpar most of the factory welds
are,most look like just surface welds.
I've been cleaning up and re-welding the ones on mine also.

[calj737]

I'd love a gas bronze welded frame from the English bloke who makes the Seely official repros. Don't want the Norton motor, but would love to commission a frame for a different power plant.

Factory welds: some aren't pretty, but all are pretty dang strong. Especially given the day they were made. Modern metals and techniques would put them to shame but they've held up for 40 years without letting go, so they did pretty well. Like you, I'll dress them up for good measure.

[SOHC4 Cafe Racer Fan]

It's more of a "restore" the welds than "improve" the welds. I harbor no illusions that when done this motor is too much for the stock frame, but given how much corrosion ate on this thing (see page 1) I think it's prudent to re-rum the welds.

These are the sections i was talking about, they have 3 spot welds, welding them up is a good idea when using modern brakes i think......

Mick,
That makes good sense.  Most people think of frame flex and stress from turning and added power to the motor.  Adding 21st Century radial mounted monoblock brakes will definitely add a good does of stress under braking forces.

[Retro Rocket]

Yes, a well made frame is a work of art...

Suzuki XR69 {gs1000 powered} formula one frame

[SOHC4 Cafe Racer Fan]

I'd love a gas bronze welded frame from the English bloke who makes the Seely official repros. Don't want the Norton motor, but would love to commission a frame for a different power plant.

Factory welds: some aren't pretty, but all are pretty dang strong. Especially given the day they were made. Modern metals and techniques would put them to shame but they've held up for 40 years without letting go, so they did pretty well. Like you, I'll dress them up for good measure.

I think you are referring to Roger Titchmarsh, who makes the Seeley MKII chassis for NYC Norton -- works of art: 17 gauge Reynolds 531 tubing hand bronze-welded with oxy-acetylene.  24 lbs!  http://seeleynorton.com/technical/mkii-chassis

I met Kenny Cummings (NYC Norton) at Corsa Moto Classico last year at Willow Springs, California.  Very nice guy and outstanding bikes.  He drove all the way from NY in a Sprinter van with his bikes for the ARHMA racing.

[SOHC4 Cafe Racer Fan]

Those Deutsch connectors are pretty cool. 

I've seen heavy duty connectors on the MotoGP and WSBK bikes to quick connect/disconnect electronics and data-logging connectors.  The stuff looks like it's MILSPEC designed for aerospace.  Galfer/Spiegler makes similar looking connectors to quick connect/disconnect brake lines.

[calj737]

Right idea, wrong application, Don. Those pictures are for "data" not for "current". Most of the connections seen in those pictures are for logger and ECU controls. Similar goal though.

Yep, Roger is the man. I knew the name and about Kenny's bike, just being discreet.

Retro, I've seen that frame before too. I have a picture of it on my laptop as the desktop 

[SOHC4 Cafe Racer Fan]

Right idea, wrong application, Don. Those pictures are for "data" not for "current". Most of the connections seen in those pictures are for logger and ECU controls. Similar goal though.

Yep, Roger is the man. I knew the name and about Kenny's bike, just being discreet.

Retro, I've seen that frame before too. I have a picture of it on my laptop as the desktop 

Cal,

I knew the difference but those data connectors are way cool looking!

I gave you a high probability of knowing RT. There are only so many people making a frame of that quality for a specific make.   I posted the link to let the uninitiated know. The frame looks so much better in person.

[MRieck]

Yes, a well made frame is a work of art...

Suzuki XR69 {gs1000 powered} formula one frame

Wow....that looks really, really, really nice. I hope it works as great as it looks other wise it should be in a museum. Brilliant execution.

[calj737]

Finally a frame worthy of housing a JMR Porting work product  Best of the Holidays and New Year to you, Mike!

I think the frame pictured (more accurately, from the welder) that was designed for a CB750 would make the ultimate house for a Rieck Billet block 1Litre, Stage 4 power plant. Some sexy Ohlins up front and out back, a MGP CalFab holding some über cool Kineo spokers, and big breathers.... I can almost envision it...

[MRieck]

Finally a frame worthy of housing a JMR Porting work product  Best of the Holidays and New Year to you, Mike!

I think the frame pictured (more accurately, from the welder) that was designed for a CB750 would make the ultimate house for a Rieck Billet block 1Litre, Stage 4 power plant. Some sexy Ohlins up front and out back, a MGP CalFab holding some über cool Kineo spokers, and big breathers.... I can almost envision it...

That is tempting for sure....a real "legacy" motorcycle. I wonder what my sons would do with it? I'd have to bolt on my TMR's just to complete the package. I do have sets of 72mm flat tops coming for the 1020cc kit.
 Happy New year back at you!

[Retro Rocket]

Yes, a well made frame is a work of art...

Suzuki XR69 {gs1000 powered} formula one frame

Wow....that looks really, really, really nice. I hope it works as great as it looks other wise it should be in a museum. Brilliant execution.

Its made by a company in the UK, they make replica XR69 race bikes in both mono and the original model with twin shocks, they work alright...    Frame pics at the bottom of the page...

http://www.silverstonesuperbikes.co.uk/xr69_5.html

[calj737]

Yep, you can tell Titchmarsh's frames as his welds never show the beads. Must be the technique he uses results in more of a "solder" type weld.

[bwaller]

Mick, the savings could be nearly twenty pounds especially with an alloy arm.

[calj737]

Brent - happen to know the weight of the stock 550 frame with stock swing arm? I'll be interested how this model turns out after the "surgery"

[SOHC4 Cafe Racer Fan]

I'm sure Brent shaved a few pounds on his race bike going from the stock tube and pressed steel frame/swingarm to his chrome-moly CMR Drixton frame and chrome-moly boxed swingarm.

[bwaller]

I surely don't want to start an argument about mild steel, CrMo, or Reynolds tubing for frame construction because I'm no expert. Often we hear of 20lb weight losses comparing OEM vs aftermarket. I have read that tubing strength between the options are actually quite similar. If frame builders use thinner wall tube, it will be lighter, but theoretically more prone to flex if the design remains the same as stock. Denis Curtis tells me Chromoly is his tubing of choice that it is stronger so thinner wall is possible considering the design is different. I'll not disagree with him! Several here including Rob (Voxonda) thinks the CB750 frame is actually quite a good frame. Certainly the British motorcycle industry made different claims! 

Don you mentioned how my chassis mods would be lighter, but that's not the case. Actually the steering head/backbone part removed was replaced with more tubing, so the weight is practically identical, but stiffness is improved plus we were able to change the rake which is what I wanted. The swingarm weighs only one pound less than the stocker too. It is without question much stronger than the original though. Denis thought if he were to build a complete frame it might be 12-15lbs lighter than stock.

Cal, I believe the stock frame is 44lbs including the arm?? After removing unneeded frame bits like brackets, stands, etc. then welding the brackets I needed on - I saved 10lbs from stock.

Sorry to stray. I'll be watching the swingarm construction with interest.

[calj737]

I would have expected exactly that, Brent. Benefit of CroMo is weight/strength ratio.  You can use a much thicker wall and get equal weight but much higher strength.

44# sounds about right. I'll use that as a benchmark for comparisons. But remember, I'm using 0.375 wall tubing for the swing arm which is about 10x thicker! And tube is 1.25" OD. Subframe will be 1" OD x 0.125 wall so that should be lighter, but not a great deal as stock subframe was pretty light anyway.

[Riceman]

I thought I would loose some weight by changing to an
aluminum swingarm,but they are almost the same.

[bwaller]

I would have expected exactly that, Brent. Benefit of CroMo is weight/strength ratio.  You can use a much thicker wall and get equal weight but much higher strength.

44# sounds about right. I'll use that as a benchmark for comparisons. But remember, I'm using 0.375 wall tubing for the swing arm which is about 10x thicker! And tube is 1.25" OD. Subframe will be 1" OD x 0.125 wall so that should be lighter, but not a great deal as stock subframe was pretty light anyway.

That stock arm must be pretty good once the wheel is bolted up. I never saw any paint cracking after stressing the part! I do remember how bloody easy it was to straighten one (in a vise with a bar) after it had been bent in an accident back in the day. 

[Retro Rocket]

Mick, the savings could be nearly twenty pounds especially with an alloy arm.

Gday Brent, up to 30% in weight can be saved after doing some more searching, the Frame I pictured about is made from T45 seamless tubing, T45 is a carbon manganese cold drawn seamless tube, as opposed to 4130 which is chrome moly...
I had to do a bit of reading to find out what T45 is, I'm used to these types of frames being made out of 4130 or Reynolds 531...
Do you think anyone would replicate the 750 frame in one of these exotic aerospace spec tubes, with some small tweaks of course...? 

Cal is this a hijack or an acceptable information session..?   

[calj737]

No such thing as a hijack on my threads. I share the addiction to frame porn as the next pevert  with the above picture as my laptop wallpaper, need I say more?

[Retro Rocket]

No such thing as a hijack on my threads. I share the addiction to frame porn as the next pevert  with the above picture as my laptop wallpaper, need I say more?

I kinda assumed that but its polite to ask....

[calj737]

I thought you and I had become close enough friends that we no longer had to be polite towards each other? As they say in España: mi thread, su thread

[SOHC4 Cafe Racer Fan]

I'm looking forward to seeing the mods.

Anyway you stack it (braced stock, boxed aluminum, Cal Fab cryo-treated aluminum, CMR chrome-moly), you will have significant improvement on the swingarm. 

Mick: that Formula Suzuki frame is pure bike porn, with those stacked dimes of bronze goodness.