on cromoly vs DOM... (I know, I know... *ducks the flying shoes*)


Wouldn't the cromo bike crashing have less impact force (F=MA, right?) than the car crashing, therefore the bike would actually take less damage?

Timmay, all this is mental masturbation.
Stresses come in all sizes and shapes and failures can be also all sizes and shapes.

Somewhere I have a long tech article on just rally and rally-cross gearboxes, from mid 90s when Escort Cossies were in WRC and there were Escort Cossies in ERC Rallycross.

All the drivers, all the gearmakers talked about the short duration/high impact stresses vs much much longer duration and lower peak or impact stress.

So while they, the various rally-cross teams all had different internal set ups with fewer gears--that was cause it was simpler and lighter and all the needed was say 4, but all agreed that there is little END RESULT difference between the high stress/high impact and short duration and longer/lower stress: stuff is going to break.

Now a cage may see a little low stress twisties of short duration, but if its done half right the cage is supported by (by being welded and/or bolted to) the shell, and as I said earlier , the sum of the 2 things is substantially stronger than each part (shell and cage) separately, so when the BIG roll type bang comes its a VERY occasional thing.

Moto-cross and enduro bikes have ONLY a frame with which to resolve constant low and high stress loads, every few feet. And the "Hours of use' per any typical year" can be astronomically higher.
Ie a typical rally car in North America may see maybe 6 hours SS time per year, or a rich guy might do 12-13 hours of SS time.

Where a experienced enduro guy may do 6 hours in one day, or if out trail riding---depending on if the guy is a silly punk "ragin' man" in the wood s or a sensible person, might do 10 hours of pounding in one day.
Bumps, bangs, down trees to ram into, wheelie over, get dropped every few feet.

Frequent high stresses to be resolved.. And only a very silly person would suggest that "Oh they have suspension" yeah an platitude. Of course there's suspension but that suspension has dampers and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure....

Now car guys don't routinely see stressed tubes down at the 1-1.25" range, nearly everything stresses or potentially stressed is min 1.5", maybe 40mm, maybe 1.75"

Those sizes are orders of magnitude stronger, or looked at the other way bike tubes are orders of magnitude weaker, yet thanks to good design and good materials, they MOSTLY work fairly faultlessly.....despite near contant high stresses..

Silly car guys could do well to study bikes an awful lot more than they do. In terms of performance they match the best rally cars ever, but with 10-20 times the reliability and 1/50 the cost.
EVERYTHING that makes a modern rally-car chassi, clutch, gearbox, a modern chassi etc is essentially30-35 year old bike stuff. Or older.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
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john vanlandingham
...and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure.

OK, you lost me here.
Can you help me understand this point? Obvously there will be stress at the mounting points of the dampers but I don't get the multiplication of the stress.

I remember when aluminum was used in homologated cages. One day the edict came down those cages weren't allowed any more and the existing cages couldn't compete. Now we all should know how strong aluminum is, depending on the spec, but the average cage builder hasn't a chance of welding it correctly.

We..sanctioning bodies and tech people, have no way of certifying welds or welders. Look at JVs strut mount issue. He can weld, used proper materials and accepted techniques and we see failures..unexpected but still there. So looking at cages we have all sorts of skill sets and equipment out there. I have no doubt that Tim could construct a cage of CroMo and it would work, others I not so sure of. If the sport went with a more exotic material then I suspect we would have to move to the certified welder program. You could use CM but only if so and so did the welding. That would drive the costs up quite a bit. Anti grassroots if you will.

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john vanlandingham

Those sizes are orders of magnitude stronger, or looked at the other way bike tubes are orders of magnitude weaker, yet thanks to good design and good materials, they MOSTLY work fairly faultlessly.....despite near contant high stresses..

Silly car guys could do well to study bikes an awful lot more than they do. In terms of performance they match the best rally cars ever, but with 10-20 times the reliability and 1/50 the cost.
EVERYTHING that makes a modern rally-car chassi, clutch, gearbox, a modern chassi etc is essentially30-35 year old bike stuff. Or older.

John, comparing bikes to cars is false comparison. The forces required to make a car go are at least an order of magnitude larger than what you will see on a bike. A competitive motorcycle is going to be around 200 lbs + a 200lbs rider. Where a rally car is going to weight at least 2,000lbs and more likely will be

The argument that just because someone did this with a bike 20 years ago is purely anecdotal. And really does not help your position. Just because someone welded it together and it did not fail does not mean it was properly or safely built.

I agree that there is some tech ideas that works well on motorcycles that would be great on cars. The bigger question I have is that if it were so easy as to look at old motorcycles why are the mainline manufacturers of race cars not doing it? Could it be that the materials or techniques that work on motorcycles do not directly transfer to cars??

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Morison

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john vanlandingham
...and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure.

OK, you lost me here.
Can you help me understand this point? Obvously there will be stress at the mounting points of the dampers but I don't get the multiplication of the stress.

That's what dampers do. To slow down the force of compression, they restrict oil flow---and I have to say the hardest thing in damping is always balancing the rate: how slow of compression damping can you go and having allowances for what we can call "square edge" bumps-----but not making it so slow the stresses "spike" or the damper basically "hydraulically locks".
But this slowing the movement down from "whatever' ---up to 15 m/s in actual tests---down to "acceptable" speed costs something: heat and stress.

Maybe the best way to clarify--as often---is to exaggerate conditions.

Imagine the work you as a human must exert to bring to a stop:
a 1200 kg car rolling t you at 0.5mph in a given distance. Call it W work.
Now imagine slowing down with just your muscles that same car in the same distance if its rolling towards you at 3 mph.
Now 10 mph, now 25mph
Velocity multiplies force at some cubed function.
To stop that car rolling at you at 5 mph is going to make you work a LOT harder than at 0.5mph.
And to stop it in the same distance if its rolling at you at 25 mph is going to make you work astronomically harder.
you are the 'damper", and you will generate a lot of heat to do the work...

And there are a whole lots of things that go up at cube of the square difference as speed or distance changes.
1 stick of dynamite under a house wall blows a big hole, but 1 measly stick 15 feet away does nothing.

Illuminating something to X brightness at 2 feet calls for X light, but to light it up 500 feet away calls for X¹⁰ or something.

wind resistance goes up insanely more than cubed.
An Opel kadett GSI needs only about 7-8 bhp top roll down the road at 100 km/hr, but that same car needs every drop of 150 bhp to go 210 km/hr---the huge majority of that being wind resistance..

Tube diameter--for given wall---goes up and strength goes up exponentially.
To quote my friend Jim Long, Senior Stress Analyst at Boeing and Saab perv, when he was marvelling at my upside-down suspension--he'd never seen anything like that--I asked "Whaddya reckon these things are stronger than that conventional STI strut there?" (with a 18mm shaft sticking up)

"Hundreds of times stronger."
Me "Hundreds???!!! "splain hundreds!"

He points to the Saab rally car "You don't make cages out of 18mm bar, do ya? you use 38 or 40 or 45mm tube and it brushes off the weight of the car slamming into the ground at whatever speed".


Slowing down the wheels costs work, the heavier the parts and the faster the speed, the 'way more" it costs. And V or velocity is a multiplier.

(I am babysitting and feeding 2 kids in the middle of this so if it ain't perfect examples, like whatever)

main point sure bikes "have suspension" but they are

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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Andrew_Frick

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john vanlandingham

Those sizes are orders of magnitude stronger, or looked at the other way bike tubes are orders of magnitude weaker, yet thanks to good design and good materials, they MOSTLY work fairly faultlessly.....despite near constant high stresses..

Silly car guys could do well to study bikes an awful lot more than they do. In terms of performance they match the best rally cars ever, but with 10-20 times the reliability and 1/50 the cost.
EVERYTHING that makes a modern rally-car chassi, clutch, gearbox, a modern chassi etc is essentially30-35 year old bike stuff. Or older.

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John, comparing bikes to cars is false comparison.

Your opinion. Opinion of MANY INSIDE the trade of rally cars readily use the comparison.
somewhere downstairs if an editorial on the back pages of the old Motoring News from a cheif high mucky muck at Ford Motorsport--when Ford ran the program---speaking of where he thought the future should lay to try and regain the broad participatory enthusiasm rallying formerly enjoyed. This is when the "World Rally Car" rules tread into power allowing the 20 off handbuilt specials which most who have been around longer than 10-11 years agree is the cause of the sports plummeting popularity we have seen, and the multiplying costs.

He had recommended banning turbo and mandating series production gearboxes, min 20 or 25,000 units.
The interviewer was aghast "performance will plumment, gearboxes won't last!!!!"

John Wheeler said, yes first year maybe, but then it will rise and mandating the use of series production gearboxes will mean that the unit cost at 20, 25k units will be fractions of the costs of the (then) current boxes.
he said "I have only to refer to any production Japanese motorcycle made in the last (x) years in terms of performance, and reliability which we can only dream of and costing mere fractions of what we spend.

See you or me or the next person can have our opinions, but this guy was employed to be at the top of the world in rally, HIS opinions are worth looking at differently.

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The forces required to make a car go are at least an order of magnitude larger than what you will see on a bike. A competitive motorcycle is going to be around 200 lbs + a 200lbs rider. Where a rally car is going to weight at least 2,000lbs and more likely will be

You're talking power/weight/gearing. Well?

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The argument that just because someone did this with a bike 20 years ago is purely anecdotal. And really does not help your position. Just because someone welded it together and it did not fail does not mean it was properly or safely built.

Don't you find it just a little well a lot arrogant that all you guys---who don't manufacture world level bikes, run FACTORIES, and RUN TEAMs winning World Championships repeatedly are theorizing and concluding things about which you have probably never ever seen?

I report what I have seen, simple facts. Sure I understand what is "happening" when you weld CrMo, I take issue with the ASSERTIONS of the
the world will end if a given 2 tubes are not normalized--with no reference to the tube wall or anything.
Its a language thing. I take issue with flat assertions like "Chrome moly is brittle" or "Gas or TiG"...when we have ample, decades of evidence showing that this is not the case.

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I agree that there is some tech ideas that works well on motorcycles that would be great on cars. The bigger question I have is that if it were so easy as to look at old motorcycles why are the mainline manufacturers of race cars not doing it?

Intertia maybe. And at the highest level, they obviously have been. Multi-plate clutches, basically scaled up motorcycle sequential bog boxes,
Long travel suspension running in front or back of the axle..
It's Deja vu all over again.

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Could it be that the materials or techniques that work on motorcycles do not directly transfer to cars??

But they do--and have been working well for decades.



It's really odd that HERE there is this fight about bikes vs cars amongst you guys yet in talks with seriously faster guys, guys that make a living at their motorsports I have seen an eagerness to discuss what ideas can be learned and maybe used to advantage, completely different reaction...

Odd.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

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john vanlandingham
Slowing down the wheels costs work, the heavier the parts and the faster the speed, the 'way more" it costs. And V or velocity is a multiplier.

Light is inverse square - but yah.
The question was less about what a damper does and more about your what I read as the multiplied stress is passed on to the frame.
"...and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure."

Correct me if I'm wrong but under heavy use the dampers (aka shock absorbers) absorb the stress, turning it into internal wear and heat. One of the things they do is stop energy from making it to the chassis isn't it.

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Morison

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john vanlandingham
Slowing down the wheels costs work, the heavier the parts and the faster the speed, the 'way more" it costs. And V or velocity is a multiplier.

Light is inverse square - but yah.
The question was less about what a damper does and more about your what I read as the multiplied stress is passed on to the frame.
"...and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure."

Correct me if I'm wrong but under heavy use the dampers (aka shock absorbers) absorb the stress, turning it into internal wear and heat. One of the things they do is stop energy from making it to the chassis isn't it.

Kieth I had my nose rebuilt last Tuesday so inside its full of disgusting stuff and swollen and packed like the worst congestion ever humanly possible, so all that backed up ick is pushing on my poor addled brain (and eyes and ears) so I'm not following what you're asking.
You gotta try and rephrase what you're asking.

All a damper can so is SLOW things down and the degree they CAN* slow things down is the degree they transmit stress to mountings. (A rigid damper like auto-x Koni crap that does not move would transmit 100% of the force entering one end out the other and either you build the chassi like a T34 or you break things)

*can because if you have some wimpy ass damper that is subjected to say 2 x the force it can deal with, it simply explodes--blows the seals out or breaks a shaft/eyelet).

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Don't worry about it - It started with an indefinate reference in your original essay.

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Of course there's suspension but that suspension has dampers and those dampers multiply stress by slowing things down---that increases stress fed into a really very lightweight structure....

My first read was that the dampers increased the stress that was fed into the frame.

My understanding is the energy being damped was absorbed (and subsequently turned into heat) by the damper and NOT passed into the frame (except, of course, the energy at the mounting points. When you run out of damping - you start breaking shit.

When I first went to high rebound shocks on my oval car I ripped the shock mounts off the car in the first 5 hot laps. The shock mounts were on the car with low rebound shocks for years with no issues. I believe this is what JVL is getting at. and seeing it with my own stuff means I have to agree with him on this.

I see the use of cromoly more for the flex benefit in other types of racing like go karts drag cars and dirt oval cars. These cars are designed around cromoly for traction more then safety.

The drag car with the air bag in the trailer isnt so the welds dont break its to keep the car from wearing out going to the track. Drag cars are re arched after every race and thrown out or sold to less HP teams when they sag to much. Kind of like balls and old boobs.

So to build a rally car out of cromoly doesnt really make sense because there isnt any traction gangs and the risk of the cage breaking in a crash doesnt seem worth the risk.

Now if I was building a race go cart for my kid it would be cromoly all the way!

The force going into the damper shaft is reacted by the mounts on both ends of the shock (unless the mount breaks, and ignoring that the car may be changing elevation slightly yada yada yada). The reaction force that is exerted by the oil/piston/valving is reacted into the shaft. By increasing the damping of the shock (compression) you are slowly turning it into a rigid member, a solid chunk of steel. The damping force is also proportional to shaft speed (pretty sure on this, maybe), so by hitting a bump fast (high shaft speed) or landing a jump, you also increase the force that must be reacted by the upper and lower shock mounts. Plus with coilovers you have the added force of the spring, but that is marginal in relation to the damping force (max spring force is ~350lb/in x 8in=2800lb) You need way more than that to stop a car from bottoming out after a jump.
So I think what John was saying is that by having dampers you increase the force going into the mount, which is true.
The dampers do turn energy into heat. That energy comes from slowing down the shaft on the dampers. That in turns creates more force going into the mounts.
If you want to see this is action, take out your springs and bump stops, ratchet strap your shocks down, and drive really fast over some rough roads.. instant impact loading. Things will break.
Not sure where all this talk about dampers got thrown into the 4130 vs 1018 came from...
We could also start a thread on how DOM is actually a welded tube and we all should be using seamless tubing to really comply with all the rules.

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Reamer
When I first went to high rebound shocks on my oval car I ripped the shock mounts off the car in the first 5 hot laps. The shock mounts were on the car with low rebound shocks for years with no issues. I believe this is what JVL is getting at. and seeing it with my own stuff means I have to agree with him on this.

I see the use of cromoly more for the flex benefit in other types of racing like go karts drag cars and dirt oval cars. These cars are designed around cromoly for traction more then safety.

The drag car with the air bag in the trailer isnt so the welds dont break its to keep the car from wearing out going to the track. Drag cars are re arched after every race and thrown out or sold to less HP teams when they sag to much. Kind of like balls and old boobs.

So to build a rally car out of cromoly doesnt really make sense because there isnt any traction gangs and the risk of the cage breaking in a crash doesnt seem worth the risk.

Now if I was building a race go cart for my kid it would be cromoly all the way!

Jeff,
The guy that owns the car just put the airbag in and said it was to keep the frame from breaking. He's pretty into this vintage thing. I don't know.

Comparing Honda transmission technology to old motorcycle frame welding is a bit of a stretch tho...

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heymagic

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Reamer
When I first went to high rebound shocks on my oval car I ripped the shock mounts off the car in the first 5 hot laps. The shock mounts were on the car with low rebound shocks for years with no issues. I believe this is what JVL is getting at. and seeing it with my own stuff means I have to agree with him on this.

I see the use of cromoly more for the flex benefit in other types of racing like go karts drag cars and dirt oval cars. These cars are designed around cromoly for traction more then safety.

The drag car with the air bag in the trailer isnt so the welds dont break its to keep the car from wearing out going to the track. Drag cars are re arched after every race and thrown out or sold to less HP teams when they sag to much. Kind of like balls and old boobs.

So to build a rally car out of cromoly doesnt really make sense because there isnt any traction gangs and the risk of the cage breaking in a crash doesnt seem worth the risk.

Now if I was building a race go cart for my kid it would be cromoly all the way!

Jeff,
The guy that owns the car just put the airbag in and said it was to keep the frame from breaking. He's pretty into this vintage thing. I don't know.

Comparing Honda transmission technology to old motorcycle frame welding is a bit of a stretch tho...

Huh?
Any reference to bike trannies was about unit cost when done in series of min 20,000.
Killer, durable, sequential trannies come free on any bike since the 50s and insanely reliable one since the 70s, and the sequential boxes in cars since oh about 92 are really just scaled up versions with a final drive....
See? about 30 years behind.
Long LONG travel suspension on cars that do gravel: about 30 years behind.

Problem is all this really common bike stuff is exceedingly rare on cars, thus its 15,000 bucks for a bad ass car tranny, and incalculably rare and expensive to have truly modern suspension travel.

---

John Vanlandingham
Sleezattle, WA, USA

Vive le Prole-le-ralliat

www.rallyrace.net/jvab
CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.

Quote
Robert Culbertson

We could also start a thread on how DOM is actually a welded tube and we all should be using seamless tubing to really comply with all the rules.

DOM is specifically allowed in this country so if you use that you do comply with the rules. We could also talk about because of how DOM is made the wall thickness is completely uniform. CDS starts out as a solid bar pierced by a die and the material is rotated every so often and doesn't always stay perfectly centered so you can get varying wall thicknesses around the tube. Not that it's really ever a significant difference. It all does the job fine, the design and execution is the most important part.