Hypothetical speed question, ;)
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Cargo Master
Joined: Jun 2010
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From: Iowa
Hypothetical speed question, ;)
So we all know 94mph is the wall but if there were no limiting factors and took the truck up there what would the top end speed be if you just planted the skinny pedal on a stock truck with 4.10 and 18" tires (edit rims, 275/70s)?
I don't intend on finding out myself.
I don't intend on finding out myself.
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275-65X 18s? If so, figure 32" diameter.
V10 max rpm? Some say 5500, some say 5300.
5500 rpm, 4.10 gear, 32" tire, .71 ratio in top gear (right?) = 180 mph.
in 3rd at 1:1, 128.
You might make 128 in 3rd, but you probably don't have enough power to hold OD above that.
V10 max rpm? Some say 5500, some say 5300.
5500 rpm, 4.10 gear, 32" tire, .71 ratio in top gear (right?) = 180 mph.
in 3rd at 1:1, 128.
You might make 128 in 3rd, but you probably don't have enough power to hold OD above that.
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
That has "never" been the case. Driveshafts have had critical speeds where they will fail since the first driveshaft was built.
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Cargo Master
Joined: Apr 2013
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From: Central Florida
Slight imbalances adding up to catastrophe?
Are you saying its it’s like a tire having a max speed rating?
And your video posted above- why is that car capable of going 120mph if the manufacturer is aware of the driveshaft failing at that speed? I thought everything was supposed to be overengineered and detuned.
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Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
Yes, it's similar to a tire having a max speed rating. If you exceed the critical speed of a driveshaft it comes apart as shown in the Mustang video above.
I once exceeded the critical speed with a prototype driveshaft in an F-250. The rear end came off the ground as it pole vaulted the rear driveshaft on the freeway. That was exciting. When I hit the critical speed the truck started to vibrate heavily. I immediately knew what it was and hit the brakes as hard as I could. I wasn't fast enough. The shaft flew apart. This was at about 60 MPH. This truck had a modified driveshaft with a torque meter installed. I had forgotten that the max speed on this truck (because of the prototype driveshaft) was 55 MPH.
The car is NOT capable of exceeding the driveshaft's critical speed. Obviously someone added an aftermarket tuner to remove the governor.
I once exceeded the critical speed with a prototype driveshaft in an F-250. The rear end came off the ground as it pole vaulted the rear driveshaft on the freeway. That was exciting. When I hit the critical speed the truck started to vibrate heavily. I immediately knew what it was and hit the brakes as hard as I could. I wasn't fast enough. The shaft flew apart. This was at about 60 MPH. This truck had a modified driveshaft with a torque meter installed. I had forgotten that the max speed on this truck (because of the prototype driveshaft) was 55 MPH.
The car is NOT capable of exceeding the driveshaft's critical speed. Obviously someone added an aftermarket tuner to remove the governor.
Cargo Master
Joined: Apr 2013
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From: Central Florida
Very interesting.
So what factors go into the decision of a driveshaft’s max speed?
And how can that calculation be so accurate that your example was rated at 55 and it broke at 60? There must be some science to this.
So what factors go into the decision of a driveshaft’s max speed?
And how can that calculation be so accurate that your example was rated at 55 and it broke at 60? There must be some science to this.
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
There is science to this. But I don't know it. That was someone else's responsibility and I never bothered to learn how it was done. I just learned that they knew what they were doing.
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Cargo Master
Joined: Jun 2010
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From: Iowa
Ok, if I get stupid enough to try it, cage the driveshaft. Check. Lol
Edit, it's just impressive how hard it hits the wall/limiter, no intention on trying to lose my license or anything. Lol just curious.
Edit, it's just impressive how hard it hits the wall/limiter, no intention on trying to lose my license or anything. Lol just curious.
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Cargo Master
Joined: Jun 2010
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From: Iowa
Going to double post, not going to call the driveshaft theory BS because if it is slightly unbalanced it will go boom but if it's true it will not. It would be rather exciting to find out if it wasn't. Lol
Frmr Ford Trans Engr
Joined: Aug 1999
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From: SE Florida
So you're saying a true driveshaft can run at any speed?
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Cargo Master
Joined: Jun 2010
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From: Iowa
No, centrifugal force will take affect some point (boom). A pipe can only spin so fast but a balanced one can spin significantly faster.
edit, make that can spin freaking faster.
edit, make that can spin freaking faster.