FrontEngineDragsters.Org Forum
Drag Racing Discussions => Front Engine Dragsters => Topic started by: PSweeney on April 24, 2017, 03:29:33 AM
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Last time I ran my car it hit the bar pretty hard, to the extent it broke the wheel. It's 138in with SBC shorty glide close coupled. Motor is 420in SBC injected on alky, making c 600bhp and 500ft lbs ish. Rear gear is 3.7 and it's on 33x10's
Chassis is CDS I have a full size battery ahead of the motor and a moon tank but little else further forward. We knew we'd need weight but hoped to calm it with 3.7 gear. Before we go back out with it, I'm making a weight bar to mount in the front axle. Lead shot is expensive so I'm smelting lead roof flashings. So far I've got it to 22lb and the material I have will see it total 35lb.
Does anyone have an opinion on how much weight I'll need ?. If I need any more I'll have to fab boxes to sit in the chassis also.
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If it is hitting the bar hard enough to break the wheel it sounds as if the bar is set too high and/or the car is hooked too well. I generally like to run the bar so that the wheel is around 1 1/2-2" off the ground but that number will vary with how rigid the bar is. I would try varying the bar height and/or the tire pressure to get a bit of wheel speed leaving and stop the car from rotating hard.
Roo
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When adding weight to set balence, it does not have to be pretty, just safe. When the proper amount is figured out then steps can be made to clean up the looks.
I hear the Parks has some new "Lite weight" bars available--- Ti tubing filled with aluminum shot and clamps to the frame with Mag brackets ;D
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I'm sure they could build some nice ones; all it would take is a short phone call and a lot of $$$$:)
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Steve Field is running about 50lb in his car, which is 148 inch, so I would try close to that best bet is have a word with him.
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If it is hitting the bar hard enough to break the wheel it sounds as if the bar is set too high and/or the car is hooked too well. I generally like to run the bar so that the wheel is around 1 1/2-2" off the ground but that number will vary with how rigid the bar is. I would try varying the bar height and/or the tire pressure to get a bit of wheel speed leaving and stop the car from rotating hard.
Roo
your correct Roo, it was a midnight special welded up hours before the event, bar was probably 3in off the ground and we'd run out of adjustment. I'll get it down lower, just need to source a decent wheel for the bar
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Steve Field is running about 50lb in his car, which is 148 inch, so I would try close to that best bet is have a word with him.
spoke to him last year on it, and he added the weight after the mishap off the line. I can't fit much more out front so I think it'll have to be a box in the chassis or drill and fill the front axle.
(http://imagehosting.rodsnsods.co.uk/23258fe34b6b4eb4.jpg)
(http://imagehosting.rodsnsods.co.uk/23258fe34b72ea2a.jpg)
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We use flat lead plates poured to fit in the nose cone
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When adding weight to set balence, it does not have to be pretty, just safe. When the proper amount is figured out then steps can be made to clean up the looks.
I hear the Parks has some new "Lite weight" bars available--- Ti tubing filled with aluminum shot and clamps to the frame with Mag brackets ;D
I watched Lee Beard bolt a weight bar to a chassis with Titanium bolts. :o
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spoke to him last year on it, and he added the weight after the mishap off the line. I can't fit much more out front so I think it'll have to be a box in the chassis or drill and fill the front axle.
Bugger, the problem with putting it further back is you'll need even more.
There is always a way round it :-)
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spoke to him last year on it, and he added the weight after the mishap off the line. I can't fit much more out front so I think it'll have to be a box in the chassis or drill and fill the front axle.
Bugger, the problem with putting it further back is you'll need even more.
There is always a way round it :-)
The way that Brisette did it back in the day. :P
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If you run a index, and tune up & down to the number, who cares about weight. Carry over 100# on the frame behind the axle and still lifts the front wheels and buries the rear trying to drive underneath the front weight
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well, I had a little win today, scored 30lb of used lead for the equivalent of $12, so tonight I'm smelting more lead and going to try making shot 8)
My axle is a 1/4in thick, anybody see an issue drilling and tapping a 3/8th hole to fill it with shot ?
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I want to say whoever did my front axle used 1/4" pipe. I cant imagine 3/8" being a problem though.
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When adding weight to set balence, it does not have to be pretty, just safe. When the proper amount is figured out then steps can be made to clean up the looks.
I hear the Parks has some new "Lite weight" bars available--- Ti tubing filled with aluminum shot and clamps to the frame with Mag brackets ;D
I watched Lee Beard bolt a weight bar to a chassis with Titanium bolts. :o
Sort of off topic. What is strength of Ti. vs grade 8?
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When I build a front axle, I drill a 5/8" hole in the spindle boss and weld it with the hole towards the axle tube. You can then hold the axle straight up and pour the shot thru the king-pin opening into the axle and seal it with the spindle king-pin instalation.
Ti bolts offer the strength of steel for the weight of aluminum but are really not any stronger as there are different grades, also Ti is notch/scratch sensitive, and if you back it with anything coated with cadnium it will errode the Ti.
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Thanks Bruce my axle is full!!!
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Add No Weight.
Kills E.T. & MPH. Costs money, Harder to push, looks Ugly.
Launch in High Gear. adding a Safety Lock-out Button to avoid down shifting, if a two speed.
That will calm that lil shorty down. Cost you maybe two tenths in E.T. and you keep MPH.
Plus no shifting means (one less thing) equally consistency.
My Daughter's car is a 174" triple slip joint, BBC 550 HP, Turbo400 3 speed, 370 Gear, 10.5x31x15 M/T tires. No-Electronics.
Launching in 2nd gear, only Costs us about two tenths E.T. No MPH loss 1/4 mile. Calms the car enough to keep the front down.
First gear launch, car will carry the front about 30' landing back down about 50' out, running a .100 faster at the 60'.
Enjoy
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adding weights to balance the car is no bad thing, it doesn't have sufficient weight over the axle to steer at speed or with the chute out. It was always going to get weight added, it was just a question of how. I now have 38lbs in my weight bar and with a properly adjusted wheelie bar and some wheel speed, it should calm it down.
High gear is an option, but I'd be concerned at reaction times and trans temps. I wouldn't do it without a valve body change to retain the transbrake and I don't like leaving off idle.
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Add No Weight.
Kills E.T. & MPH. Costs money, Harder to push, looks Ugly.
Launch in High Gear. adding a Safety Lock-out Button to avoid down shifting, if a two speed.
That will calm that lil shorty down. Cost you maybe two tenths in E.T. and you keep MPH.
Plus no shifting means (one less thing) equally consistency.
My Daughter's car is a 174" triple slip joint, BBC 550 HP, Turbo400 3 speed, 370 Gear, 10.5x31x15 M/T tires. No-Electronics.
Launching in 2nd gear, only Costs us about two tenths E.T. No MPH loss 1/4 mile. Calms the car enough to keep the front down.
First gear launch, car will carry the front about 30' landing back down about 50' out, running a .100 faster at the 60'.
Enjoy
I agree launching in 2nd will settle it down, but....respectfully disagree on other stuff.
Ur running a 3 speed. 2nd gear in a 400 isn't 1:1...more like 1.48:1. You loose more ET with glide (normally aspirated) cause 2nd gear is 1:1.
With pro tree.......hard to get good reaction time in lunching in second (unless you have trans brake that works in second). If racing full tree and foot brake it's a moot point.
I have a 140" WB, SBC making about 420 hp, glide w/brake and 30 x 10.5 inch tires....and no wheelie bar.
Impossible to get out of the hole in first at full throttle with no weight on front when using TB. 60 ft times were abysmal.... I had to launch in 1st for reaction time and shift to second .2-.3 sec into run to keep front down. Really ate into the ET. If racing and index or dial in that's not a problem. I just wanted more ET out of the car to see what it can do.
Put 100# on front. Can launch full throttle on the brake and knocked 2 tenths off 60 ft time. Goes straight as an arrow. Also picked up 3 tenths at 1/8th shifting 1.5 sec into the run.....which is no where near the 7k rpm it needs to shift at.....so there's WAY more in it.
And with how well the fronts planted...have room to remove some weight off the front if I want...but seems to have a good balance now.
I know guys running 7.0 pro with 300# of weight on front, cutting 1.1 60 ft times and never touching the wheelie bar. Didn't seem to slow them down much....lol
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As a long term solution would you consider moving the engine "out" further from the axle CL? I did that on my wheelstand prone Logghe altered (moved the engine 7 in. forward) and it turned it into a totally different (tamer) animal, without the penalty of added weight. This solution addresses the real elephant in the room.
(http://img.photobucket.com/albums/v608/6racer/LOGGHE%20T/trp2013_1448b_zps38e815ce.jpg) (http://smg.photobucket.com/user/6racer/media/LOGGHE%20T/trp2013_1448b_zps38e815ce.jpg.html)(http://img.photobucket.com/albums/v608/6racer/LOGGHE%20T/loggheT01.jpg) (http://smg.photobucket.com/user/6racer/media/LOGGHE%20T/loggheT01.jpg.html)
Prior to moving the engine I was using 80 lb of lead on the axle. Note wheelie bar positions.
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7 inches is a bunch to move an engine, not from a weight standpoint, but a chassis design/engineering potential issues. Adding weight is the quickest way to garner results in the beginning, later on if a new chassis is to be built, one can use that information in order to move things/engine around to achive the same balence as adding the weight did with design and engineering
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FULL DISCLOSURE: I should have mentioned I DID front-half the entire chassis - after an intimate head-on encounter with a seductive concrete guard wall.
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No way would I move the motor out, it's purposely built to emulate a 60's digger. I have 38lb in a weight bar, some shot to fill the axle and more lead for a weight box.
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7 inches is a bunch to move an engine, not from a weight standpoint, but a chassis design/engineering potential issues.
TRUE
I mis-spoke. I lengthened the wheelbase seven inches while moving the engine out two inches. The other five was to make room for a radiator and alternator so I could drive it around without being towed on the end of a string. I guess not having to get a tow back from the big end doesn't make it nostalgic anymore too.