16 replies to this topic

[mariner]

Lots and lots of pure power here 

 

https://www.enginela...400-horsepower/

 

 

Very wisely I think nobody stands near the car when its under load !

 

 

What is interesting  is how much the nose of the casr rises despite a very strong looking hld down strap under the nose .

[gruntguru]

Not that long ago, top fuel was making similar power - with nitro - and replacing rods and pistons after every pass. That motor did 8 pulls in a day with no maintenance.

 

I just watched the whole video. You can see the turbo blanket on the driver's side being pulled toward the compressor inlet. Needs to be better secured of course but - it suggests pretty extreme air velocity to the side of the inlet - I would be trying a small bellmouth on the turbo inlet.

[Slumberer]

“This thing is making 5,400 [horsepower] to the hubs — I guarantee you this thing is making 6,000-plus horses to the crankshaft,”

 

That seems an awful lot of drivetrain losses, or am I missing something?

[Greg Locock]

Diffs are horribly inefficient. But try and find any measured numbers on that and I'll bet you are out of luck. 85% is the usual guess, it isn't far wrong. Around town they are worse.

[gruntguru]

So 0.15 x 6000 = 900 hp

 

Need a very big radiator for that diff.

[GreenMachine]

Are those sorts of drivetrain losses linear with power output?  Revs?

[Greg Locock]

Complex, to say the least. There's very little published literature on it which is odd since the instrumentation -driveshaft torque strain gages and wireless transmitter-is commercially available

 

https://metromatics....a torque sensor.

[Greg Locock]

Quick literature survey

 

https://www.geartech...es/0786x/Yu.pdf

 

There is an SAE paper but it didn't pop up

[GreenMachine]

Thanks Greg!

[gruntguru]

[Greg Locock]

NFW, for hypoids

[404KF2]

Worm on my 1966 404C! 4.25:1

[MatsNorway]

How does one make a hypoid overlap with the Helical Bevel? And why does the graph start at 0?

 

Hypoid i new was bad. But I am assuming they run Helical in a drag car.

 

But don't you get a little bit of extra ratio possible with hypoid? You sort of do the worm gear thing. More sliding less pushing.

 

1:1 worm made me curious, is this graph from a theoretical/mathematical paper?

 

Here is a sketch i found on a possible 1:1 worm. I struggle to see the engagement after a full rotation. It seems a 1 : 1 worm would function/look differently than the normal worm gear.

 

https://i.sstatic.net/o4tU7.jpg

 

 

Is Manolis? still around? he could pull of a model better i guess. Autodesk Inventor does not allow me to go below 1 : 6 on worm gear.

 

Tried to make a screw with a 1:1 ratio on the coil and a counterpiece. I managed to constrain them and it moves to a point. But a full rotation is beyond my modelling capabilites. At least with only a few minutes of fiddling.

 

Even with 1:1 on each coil sweep it looks to be not 1:1 Ratio.

Edited by MatsNorway, 14 February 2025 - 10:44.

[Greg Locock]

grunguru's graph ignores the huge effect of stiction and other low speed friction effects. Crucially it also assumes constant mesh engagement, whereas a real hypoid diff is only correctly meshed at one torque. That's why when you set the pinion clearance it is a compromise. If you set it to be perfect at 50% torque then at full torque the losses go through the roof, and if you haven't got it perfect at a sustained power (eg towing up a hill) then again the oil cooks.

Edited by Greg Locock, 14 February 2025 - 22:52.

[gruntguru]

Yeah, I did find it on an industrial gearing site where gearboxes often find themselves in constant torque applications.

[Lee Nicolle]

Diffs are horribly inefficient. But try and find any measured numbers on that and I'll bet you are out of luck. 85% is the usual guess, it isn't far wrong. Around town they are worse.

A 9" Ford based diff consumes horsepower and produces a lot of heat,,in the oil. When I was racing  in the 90s using them I used various oils. Normal 90 weight,useless!! limslip 90, vegetable oil LSD oil that was the best. The vegetable oil though got hot and stank,, I have very little sense of smell but it near made me sick!!  Gears however looked good. 12 lap race and you could not touch the diff housing. Too hot! Needless to say it was changed every meeting.

These days I use synthetic LSD 80/90. Designed for truck diffs. Gets nowhere near as hot, does not stink [at least to me]  And it stays clean. This in 78 Dana diffs. There is specialty oils that are supposed to be better. The Redline stuff is defenitly sticky, still beaded up on diff remains. When a cap bolt broke, allowing the gears to then break.

In the Austin A90 diff is the Supermodified heat is considerably less. Not that that diff has ever had a real issue. But250hp running through a 15" wide rim and tyre is a lot of drag. Most of those guys, classic supermod are using synthetic. In old Halibrands with Ford V8 style gears the gears no longer fail, with the bigger Champ diffs they do not get as hot.

Sprintcars all use synthetic diff oils or they simply eat up the gears really fast.

 

With this Promod they are often using s adiff that looks ;like a 9" just far larger and more expensive. Stonger in every respect but also [as a complete aluminium billet piece] still heavier and I feel sure a good eal more drag as well.

[Greg Locock]

Do you ever measure the diff temperature? I remember 150C as the limit, which made the diff oil guys feel sick, I think they wanted 130.