Ratio of tranny angle to drop height

[Req]

Anyone have any ballpark numbers for this, or is it all dependant on speed?

[corey@nsmb.com]

Good question...I am gonna tune into this one.

[Taylor_P]

mimimum 50 degrees maybe? 45 perhaps? bigger drop, steeper tranny. i dunno

[chauncy]

I don't think there is any set number. I've never seen anybody measure the angle of a tranny before. It would be pretty cool if someone found that out though. It probably would depend greatly on speed, rider and the bike. I guess you'd need a steeper tranny for a hardtail cause all the shock goes into the bike.

[RyanH]

I know a way hold on I'll make a pic.

[RyanH]

You make the tranny inline with the edge of the drop, it depends on the gap. Small gap steeper tranny Bigger gap flatter tranny.

Its why bender needs a really steep tranny on the jaw drop to land it because he drops basically vertical.

[gooch]

Originally posted by RyanH
You make the tranny inline with the edge of the drop, it depends on the gap. Small gap steeper tranny Bigger gap flatter tranny.

Its why bender needs a really steep tranny on the jaw drop to land it because he drops basically vertical.
You need to add speed in there though
Depending on the speed you hit it at, it will change the angle of approach

[RyanH]

Ya exactly the size of the GAP :rolleyes: you know you have to make the gap and you always hit a drop with about the right speed you don't want to go fast off a vertical drop with no gap.

[Req]

The method I've heard is roll a couple rocks off the top at the best guessed speed that you'll be leaving the drop.

[|)uR0 .243]

Originally posted by Req
The method I've heard is roll a couple rocks off the top at the best guessed speed that you'll be leaving the drop.

i never thought of it that way but i won't depend on rocks to see how to do a successful drop.

[Midas]

Just keep 'em steep to keep 'em smooth.

[chauncy]

That's what I do and it works off drops, but it doesn't factor in suspension soaking up the lip on dirt jumps.

[RyanH]

My way works best because you can make a tranny too steep, and if that happens you will land flat if you go a bit too fast.

Remember when building:
Small Gap - Steep Tranny
Big Gap - Not so steep

[barry]

i once thought the straight line thing worked, but it doesnt. now i will tell you why... here goes

when you leave the ground, you stop accelerating in the X axis, but gravity accelerates you in the Y. therefor you fall in an arc. theres a formula to find the perfect angle, but you need to know the amount of height and distance first....
i'll make an attachment hang on.

i love this topic :D

[bullit_kid]

wait till m33p reads this thread

[Midas]

Originally posted by RyanH
My way works best because you can make a tranny too steep, and if that happens you will land flat if you go a bit too fast.

Remember when building:
Small Gap - Steep Tranny
Big Gap - Not so steep




why not just put the tranny in the right place and keep it straight and learn how to land in the right place?

[barry]

omg this is rad

[Req]

Originally posted by Barry
omg this is rad

Wheres the attachment! =P

[barry]

im working on it....

it'll be worth it...

[synchro]

School time.

The size and angle of your tranny depends on a number of factors. We have:

1. Height of drop
2. Length of gap
3. Take-off angle of the jump
4. Length of the run out
5. Take-off speed

There are two generalities we can look at.

For drop with a long run out, as the height of the drop increases the angle of the tranny should get steeper so that it is taller AND longer.

For a drop with a short or limited run out, as the height of the drop increases the angle of the tranny will get steeper but the lenght of it does not change. For drops with a short or limited run out and short tranny, the tranny will be steeper than one for a same size drop with a long run out.

So, let's say you have a 10ft drop with a flat take-off and a 4ft gap. As the gap is small compared to the height of the drop, you won't need a lot of speed to clear it. Therefore, the tranny doesn't need to be very long. In terms of the angle, something around 25-30 degrees would work well. A 30 degree tranny would be 4ft high and 7ft long.

If you want to figure out the size of your tranny using angles you will need a scientific calculator that has a tangent function. You also need to know about trigonometry. This link is pretty good at explaining it.

trigonometry help (http://wright.nasa.gov/airplane/trig.html)

Good luck!

[barry]

i give up

[RiDiCuLoUs]

as long as its smooth!!!!:D

[Freestyler]

ratio? 14/19 = 0.7868

really i dont know... there seems to be no set rule. there really isn't a science to good riding. maybe there should be? then everyone could calculate numbers and pull out their calculator out before they do a drop? ( like i did with 14/19 )... food for thought i guess. it will be interesting on what comes up in this thread.

Cheers

[synchro]

I've never used a calculator to build a tranny, but I just wanted to show how it can be done using a few smarts. In building experience is the key. I can eyeball stuff up and get it pretty much bang on to how it should be. In reality it doesn't matter if you're off by a few degrees. On landing I don't think any of us could tell the difference between a 30 degree or 45 degree tranny anyway.

I always use my calculator on rides though so I can calculate my proper take-off speed for road gaps and and what my tire pressure should be for those rainy days.

[Keefer]

You know, regardless of your horizontal speed, you hit with the same vertical impact. And the dude that says to line it up with the lip of the drop, you're wrong. You take a curved path through the air cuz you're always at a vertical acceleration, but not a horizontal one when you're in the air.

[synchro]

Originally posted by Keefer
You know, regardless of your horizontal speed, you hit with the same vertical impact. And the dude that says to line it up with the lip of the drop, you're wrong. You take a curved path through the air cuz you're always at a vertical acceleration, but not a horizontal one when you're in the air.

Your "vertical impact" will increase with the height of the drop because acceleration due to gravity ("vertical acceleration") is acting on you for a longer period of time.

[switch]

As time increases, horizontal speed decreases (air friction).

As time increases, vertical speed increases (to a point - have to account for air friction).

Theoretically, the angle at which the bike will impact the horizontal plane increases with time.

[chauncy]

Wow...

[Keefer]

Originally posted by synchro
Your "vertical impact" will increase with the height of the drop because acceleration due to gravity ("vertical acceleration") is acting on you for a longer period of time.

Haha, thanks for pointing that out. You basically said, the bigger the drop, the harder you hit. I said going faster off a drop does not make you hit with any additional impact.

vit + 1/2at^2 man.

[Craz]

Ideally a dirt jumps tranny should look exactly like the jump itself.

[FruitOfTheLude]

its not the tranny its the rider. just build it and ride it, you have to be pretty stupid not to be able to tell if the tranny is right. its just a feel. like at the top of our lolo trail we have a 6 foot drop to near flat that is smoother than a lot of tranny drops just because who the fuck knows. jsut ride it and see. dont waste your time with math this is biking for godsake.

[synchro]

Yeah you're right bro, just eyeball it up and ride smooth. But the dude asked a question about how to build the right tranny so I gave him some good advice. If you've never built a dop/gap with a tranny before telling someone to just eyeball it up it isn't really a lot of help.

[Req]

Originally posted by synchro
Yeah you're right bro, just eyeball it up and ride smooth. But the dude asked a question about how to build the right tranny so I gave him some good advice. If you've never built a dop/gap with a tranny before telling someone to just eyeball it up it isn't really a lot of help.

Yah thanks for that info, that was actually what I was looking for. I'm not actually building a jump, I was just curious about a ball park figure for a jump, cause I don't feel like I could look at a tranny right now and know if its right or not, but your comments help. Think I have a better idea of what one should look like w/o having to ride it.

[Nelson]

If you honestly want to know all that jazz send Gandalf a call....he did that as his grade 11 final math project.