Drag Bike swing arm lenth

[TecateDan]

Okay Draggers. What are the pros and cons of an extra long swinger? What are people running out there? It's no secrect John and I have a 500 comming to TF but we're debating how long to make the swinger.

[El Camexican]

Rigid or sprung?

[jeffatc250r]

The only drag you do is down in p-town, fag!
I say run it stock length and learn how to lean. I made a extended one for my 5-hundo and quickly ditched it.

[TecateDan]

Rigid or sprung?

Sprung but I was wondering if you need a bump stop of some sort??

The only drag you do is down in p-town, fag!
I say run it stock length and learn how to lean. I made a extended one for my 5-hundo and quickly ditched it.

I plan on runing the +3 that I built for my Tecate on there most of the time Jeff but am building a seperate swinger just for dragging at TF. 4-snows on backwards and fabio sitting on the seat aint gonna keep the front of that 500 down when it hooks up on the track. My 250 would stand right the F up when it hooked up let alone the 500!!!

[JasonB]

+8, and put a 30 pack of beer on fabios lap.

[Xowner]

For the best do a plus 4 or 6 and move the front end out, after you get past a 6 the weight isnt over the tires.....

[El Camexican]

Sprung is always better than rigid if you can make the rest of the parts work. Are you putting a wheelie bar on it? If so make sure it won’t dig in at speed. Length makes anything go straighter (rifle VS pistol) but more length takes more power to get moving. A Top Fuel dragster is a lot longer than a 8 second gas powered bracket dragster. It has something to do with the energy needed to load the chassis with energy and “lift” it before it can move forward. Too much chassis for a given motor is as much of a problem as having too much engine for a chassis.

Then there is steering. The longer it is the worse it will steer. If you add a bunch of length to the swinger it won’t be much fun on trails. If this is a drag only machine and can lite the skins at will I don’t think you can go too long, but don't over do it, maybe 4" to 8'?. It takes HP to spin chain and you need some weight on the axle. Keep in mind that if your swing-arm pivot is taller than your rear axle adding length to the swinger will raise your center of gravity and steepen your steering-head angle. That all adds up to less weight on the rear wheels, so if traction is an issue then you will want to compensate in your design to keep as much weight on the rear as possible. Maybe an adjustable strap to use just for drags? I’d also leave a place to bolt some ballast on the swing-arm if you can, might come in handy. Then the issue of the added movement of the extended axle, you mentioned a bump stop. I’d make provisions for one, but you won't know till you check the movment with the spring off the shock. Maybe make it adjustable as well? I’d also consider a steering damper. You can get a cheap one at Pingel or fab a bracket to use at take-off damper from a stock street bike.

[fabiodriven]

For the best do a plus 4 or 6 and move the front end out, after you get past a 6 the weight isnt over the tires.....

I don't think I would have thought of that Honnerlaw. Thanks for the knowledge. I don't think we'll be doing that though. Even though we are going to give the drags hell with this machine, it is going to be an all-around rider, not just a dedicated drag bike. If it were a dedicated drag bike I would definitely stretch the front out after your suggestion.

[TecateDan]

Agree with fabio and all that has been said. The first gen tecate is already a -2 in reality so it looks like +8 or +10 is in order. Will need to mock up and see where center of gravity is. I smell experiments in the future.

I don't think I would have thought of that Honnerlaw. Thanks for the knowledge. I don't think we'll be doing that though. Even though we are going to give the drags hell with this machine, it is going to be an all-around rider, not just a dedicated drag bike. If it were a dedicated drag bike I would definitely stretch the front out after your suggestion.

[TecateDan]

Luckily I have an adjustable dog bone so that can be compensated for. Also he a mini dog bone I built for Ice racing that was to small but may be perfect here.

Sprung is always better than rigid if you can make the rest of the parts work. Are you putting a wheelie bar on it? If so make sure it won’t dig in at speed. Length makes anything go straighter (rifle VS pistol) but more length takes more power to get moving. A Top Fuel dragster is a lot longer than a 8 second gas powered bracket dragster. It has something to do with the energy needed to load the chassis with energy and “lift” it before it can move forward. Too much chassis for a given motor is as much of a problem as having too much engine for a chassis.

Then there is steering. The longer it is the worse it will steer. If you add a bunch of length to the swinger it won’t be much fun on trails. If this is a drag only machine and can lite the skins at will I don’t think you can go too long, but don't over do it, maybe 4" to 8'?. It takes HP to spin chain and you need some weight on the axle. Keep in mind that if your swing-arm pivot is taller than your rear axle adding length to the swinger will raise your center of gravity and steepen your steering-head angle. That all adds up to less weight on the rear wheels, so if traction is an issue then you will want to compensate in your design to keep as much weight on the rear as possible. Maybe an adjustable strap to use just for drags? I’d also leave a place to bolt some ballast on the swing-arm if you can, might come in handy. Then the issue of the added movement of the extended axle, you mentioned a bump stop. I’d make provisions for one, but you won't know till you check the movment with the spring off the shock. Maybe make it adjustable as well? I’d also consider a steering damper. You can get a cheap one at Pingel or fab a bracket to use at take-off damper from a stock street bike.

[JasonB]

ya i threw the +8 out there because you identified in the other thread (fabio said it) the tecate was already a few inches too short stock, so 8 sounded spot on lol

[El Camexican]

How fast do you expect to get to in a drag race? If it's much past 60mph and not on a smooth surface please consider that steering damper as well as perfect braking system. Adjustable steering stops might be an option as well, real easy to add on and you can back them out to trail ride.

Watch these videos and see what happens when a fully loaded up chassis is “unloaded” at the finish line. That moment when you have to shut down is the scariest moment in drag bike racing. Every thing that was hanging on for dear life (including the driver) tries to get to pass the front wheel.

You'll see Hogan go down and listen to the fans that didn’t even see it happen clap. Everyone likes to watch the launch, but the real crazy sh*t happens when you turn off the gas at speed.

http://dragbikelive.com/news/10612/h...46-87mphvideo/

http://www.youtube.com/watch?v=ce57mFjtZpQ

[TecateDan]

Not suer what the exit speeds at TF were but I would immagine right around 60-70 tops. Not even sure how long it is I think It's an 1/8 mile (correct me if I'm wrong) THe track is groomed and pretty smooth so I'm mostly worried about launch. Stopping was no problem last year for all but one person who hit the rail but I didn't see it so may be starting rumors. Apprecite the advice though candia-mexican.

How fast do you expect to get to in a drag race? If it's much past 60mph and not on a smooth surface please consider that steering damper as well as perfect braking system. Adjustable steering stops might be an option as well, real easy to add on and you can back them out to trail ride.

Watch these videos and see what happens when a fully loaded up chassis is “unloaded” at the finish line. That moment when you have to shut down is the scariest moment in drag bike racing. Every thing that was hanging on for dear life (including the driver) tries to get to pass the front wheel.

You'll see Hogan go down and listen to the fans that didn’t even see it happen clap. Everyone likes to watch the launch, but the real crazy sh*t happens when you turn off the gas at speed.

http://dragbikelive.com/news/10612/h...46-87mphvideo/

http://www.youtube.com/watch?v=ce57mFjtZpQ

[Bryan Raffa]

longer the swing arm the longer you want the dog bone ... not shorter Ya it was groomed one year... by me and a rock rake and a few kid's .. expect CHOP!

[TecateDan]

Why longer dog bone. on the tecate longer dogbone = higher rear end? I would think you wnat the ass end lower so the weight transfer to the tires happens sooner?