straight cut or not

[k1]

good to see everybody having there say about dif ratios,we all have our own experiences to work on and its good to hear others.
Just a little confused why some people feel you need big hp to run straight cut box or drops or diff.
Helically cut gears as in standard engines were designed to be quiet,to reduce gear noise.However they require more hp to drive,therefor reducing the hp that transmits to the wheels.
Without trying to be to technical let me explain; Newtons laws of physics say"energy cannot be destroyed only converted" in helical gears they are cut at 45 degrees ,so they mesh gradually.this makes them quite but a lot of the energy is lost to sideways thrust.
in a straight cut gear the force goes straight through so friction is less therefor wear is reduced.
I ran a 3.1 dif with 1to1 drops and a standard box on 12" rims in my 1380 which made 117bhp at the crank.It used to spin the wheels in the first two gears and was a real nightmare.
I now run a 1450 with 3.1 dif 1 to1.08 timkin s/c drops and a jack knight dog box on 13" wheels with apaddle clutch and it is an absolute joy by comparison.The long first gear helps and the car make 50mph in first and eliminates a lot of the wheel spin.
you just need ear plugs so noisy. My advice is don't hesitate get straight cut all the way, you wont regret it

[monkeyjim]

anything to do with diffs and gearboxes refer to AC Dodd engine builder on the ML Motorsport website forum .

Dave

[Simon1275mpi]

Well said, welcome to the forum.

I've been using the Mrs 96spi with a 3.1 diff as to my MPI with 2.76, the 3.1 crusies nice at 70 but 80+ at a push and it just feels like it has more. I'm just in love with the 2.76 as it allows it the freedom to do 85, 100+ at a push, but without all that noise.

But I'm tempted to buy some ear plugs and go for a S/C box. ;D The S/C box just sounds right , but long for those long cruises. It's about what you want the engine/car for.

[annon]

is it the involute box you are using?

[k1]

Hi DR yes it is involuted ,makes for a easier and quicker change then the old straight dogs,especialy when you go for first at a hair pin at 30mph.I find there are two major benefits to the box over traditional baulk ring straight cut 1 you have a split layshaft so you can change 1st 2nd or 3rd ratio's and 2 it will handle 200 hp so no worries of brakages.
i think the sounds also awsome!!!!

[annon]

use the same myself and couldn't agree more with what your saying, nice to see timkins on the drops, have you tried the salisbury lsd yet set mine to 90lbs nearly tore my bloody arms off better at 45lbs for the road on jk output shafts, when you went up to 1450 did you fit 84mm stroke on s rods if so you must have nice torque and driveability.

[k1]

Hi dr i have 84mm crank with 74mm forged omega's giving1445cc .
I had a slipper in my old car and when you used to boot it in a corner it used to lock up and go straight instead of turning,im a bit right leg heavy if you know what i mean!
With the power of my new car i thought i would try a 4pin instead of a slipper,but after an indepth conversation with Terry Moore i have been advised to go slipper again and go easy on the juice.Do you agree whats your view on this topic.

[annon]

hey you know terry in ashford, had some realy good races with him, know him well, allways raced no 74

[Simon1275mpi]

slippers and a pipe - lots of smoke

[k1]

I last spoke to Terry at lyddon hill last year wespoke quite a bit about a series .I have just finished building a class 4 1127cc engine with Mick Badman for his new car,rates Terry as the Michael Schumacher of grass.
I think in his prime he won three nationals and four fastest man on grass all in mini's of a variety of sizes. These are the people who vary often don't want to speak about things they have spent a lifetime to learn,but Terry was great answered lots of questions a real gent.Although when i mentioned piper cams i think he wanted to hit me,he is a Kent cams and swiftune through and through.
Did you race him on grass at MK or IK or was you with another club, come on give me some background.
cheers k1

[annon]

i raced mk & hre as it was then mini rods 1071s then class 5/6 4th at nationals is this the sport that you will do? mick will know me as 32 is he still in hastings?

[k1]

Mick owns a garage at cripps corner now i will be out there on monday refitting his engine to his car ant taking to gerald dales befor the two day next week.One of the class ones i help build has IK 32 now so realy have no idea of your name but i will ask mick when i se him,to see if i can jog his memory.
chers k1