FrontEngineDragsters.Org Forum
Technical => Roo Man's Room => Topic started by: PalliP on July 19, 2013, 12:59:32 AM
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Hi there guys.
I have been waching here for a while and reading through your knowledge and it has helped with ideas. I have tried dragracing With only the rallycross cars I have been competing through the years. I have also been in formulaoffroad and I have built my rigs self, and had them working my self. Now I am going to build me a slingshot and try the fun what you guys subscribe on my one :)
I have built me a jig, 330 cm long to build the Cage and front of the motor.
I am going to use sbc 350 and th350 auto and a 9" ford.
1.I ordered some blueprints from Mark Williams to see how the proffs build it, are they ok to follow?
2.The drawings show a rail With no suspension front, whats Your appenion on that?
3.I want it shorter, thinkin about 160" is the suspension critical for a shorter car?
4.With that setup, would you have the motor more front and put in a driveshaft? I am nearly 2 meters long ;) so my legs are allways in the way.
IŽll put in a photo of the jigg, as you can see it is on wheels, Iam planning to work on it home and at my work, so it is easier to move it.
Hoping to learn more from you guys, thanks alot for a good page :)
With regards
Palli P
Norway.
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Pallip,
At 160" wheelbase I would consider using a torsion bar on the front--the shortest rigid car that I have built was 175". The Mark Williams blueprint should be a good guide but check with whatever sanctioning group that you will be running with to see what they require. I usually put the motor about 42" out (centerline of rear axle to back of block) on 200" plus cars although a little further out may help reduce wheelstands with the shorter wheelbase.
If you leave the start line in low gear with the th350 the torque multiplication will also have a tendency to make the car want to wheelstand. Apart from some Competition eliminator cars just about everyone uses a powerglide as a dragster is light enough that it will launch OK with the taller low gear.
Roo
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Thank you for a good answer :)
The drawing shows the width were you sit about 20", is it the "normal" Width or do you mesure Your behind for a custom mesure, then it has to bee wither on the sholder for Space for the shoulders.
Is it ok to shorten the car on the drawing and have the axle on the same place and all the tubes in Place as the drawings show!
I will bee useing twin turbo setup and stall about 3500rpm and was thinkin about launching in second, dont you think the Th350 will hold up?
I have allready built the turbo system and tryed it in a Jeep cj.
Thanks again.
Palli P
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PalliP,
20" is pretty much a standard inside width for a shoulder hoop unless you are wide across the shoulders (like Glenn). A lot of car have some taper built in with the lower rail closer together than the top as most people are narrower at the hips (although I have seen some WalMart customers that refute that reasoning). Depending on how much you shorten the car from the blueprint you need the space the uprights and cross members to match.
If you have not already seen the Hot Rod magazine story on the building of Ed Pink's Old Master it is worth a read as it explains a lot of the reasoning and techniques that went into building what was an outstanding car.
Hopefully this link will take you to the article. http://wediditforlove.com/techtalk18.html
Roo
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Way interesting article.
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20" is pretty much a standard inside width for a shoulder hoop unless you are wide across the shoulders (like Glenn).
Roo
What are you tring to say, that I'm to big
(http://www.leverfamilysite.com/images/2010_Dragster/Progress_2011_02_05/P2050016.JPG)
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PalliP,
20" is pretty much a standard inside width for a shoulder hoop unless you are wide across the shoulders (like Glenn). A lot of car have some taper built in with the lower rail closer together than the top as most people are narrower at the hips (although I have seen some WalMart customers that refute that reasoning). Depending on how much you shorten the car from the blueprint you need the space the uprights and cross members to match.
If you have not already seen the Hot Rod magazine story on the building of Ed Pink's Old Master it is worth a read as it explains a lot of the reasoning and techniques that went into building what was an outstanding car.
Hopefully this link will take you to the article. http://wediditforlove.com/techtalk18.html
Roo
Thanks, I will read it, saw it some time ago but didnt read it then :(
Glenn you are looking good, it takes a long time to build up a good traction weight :D I know every thing about that, now I have to build a rig that I can be in the middle because no lockers holds up when I sit on the left side ;D ;D
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Hi there.
I have been Reading the article about the Old Master again and again and I have a question (probably a stupid one) why is the motor lower at front, is it because of the grafity point? or is it deeper thoughts behind it? In the Old Master the motor is 8 degres lower at front.
Another thing I cant decide, that is the tire size. I have to make up my mind about that so I can build the brackets for the axle, and fasten the motor. The motor and axle are now setup as I would use 32" tires and it is 5 degrees and With 32" tires I have 9 cm to the ground up to the lower tubes. I am wondering about lowering the motor/axle to use 28" tires and then I have more room for my big as and legs as the axle goes down.
Then the damper on the engine will be about 2cm from the lower point of the tubes.
Am I thinkin this in the wrong way?
Thanks again for great answers.
Regards.
Palli
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More pics.
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Palli,
the big dump angle on the motor was how things were done back then, now most are level or half a degree down. Progress looks good on your car and I love the mobile jig. I would make one suggestion and that is to move the rear motor upright so that it is in line with the back of the block and thus will support the rear motor plate better. Doing it that way also helps seal the cockpit off from the engine bay a little better.
Roo
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Thanks for a quick reply.
The mobile jig comes in handy, because I am doing this at work :)
It sounds like a good idea to set the motor in one or two degrees, I think it will simplify Things.
What about the tiresize, am I far away with 28" or should I continue With 32". It will probably be better degree of the driver With the axle little bit lower.
What is the common ground clearance under the car? I thougth I had seen it in some regulations that 4 inch was the lowest?
The upprights is just temporary there, I was figuring the hight of the shoulder hoop.
Thanks again.
Palli
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Palli,
the minimum ground clearance in most rule books is 3" to a point 12" behind the front wheels and then 2" for the rest of the car. I usually set my lower rails at 3.25-3.5" from the front end to the motor plate and then they rake up from there. The 28" tire diameter will limit you somewhat in choices and width--I usually set my cars up to run a 31" tire if there are no specific choices by the owner. That way you can run anything from the nostalgia top fuel tire (12-13" wide) and up. With that diameter I set the axle centerline at 15" off the ground plane.
Roo
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Hi there.
I have been Reading the article about the Old Master again and again and I have a question (probably a stupid one) why is the motor lower at front, is it because of the grafity point? or is it deeper thoughts behind it? In the Old Master the motor is 8 degres lower at front.
Another thing I cant decide, that is the tire size. I have to make up my mind about that so I can build the brackets for the axle, and fasten the motor. The motor and axle are now setup as I would use 32" tires and it is 5 degrees and With 32" tires I have 9 cm to the ground up to the lower tubes. I am wondering about lowering the motor/axle to use 28" tires and then I have more room for my big as and legs as the axle goes down.
Then the damper on the engine will be about 2cm from the lower point of the tubes.
Am I thinkin this in the wrong way?
Thanks again for great answers.
Regards.
Palli
Dont get worked up on motor angle, Its a relationship of 4 things
1-Tire size and how high you mount the rear end
2- type of rear end, Fords pinion is .500" lower than Chrysler- so less angle
3- how far out the engine is from MP to rear axle CL
4-front of oil pan/ blower pulley to ground clearence
Once those are set the angle is what it is
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Hi there guys.
Thanks for all the good advises and merry Christmas!
I made some progress with my project. I lowered the axle about 3 cm and the backend of the motor. The line is now 2degrees. There is now more room for my legs ;D
I also moved the upper frame rail up so there is just enough Space the take out the last sparkplugs. I think I will have more strength in the rail that way.
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My personal preference is to have the rear end uprite no more than 1" ahead of the rear end housing as it makes the RE tighter to the frame so the chassie reacts better, too far back and the RE can dance and that magnifys if you run a really wide tire. Also at this time before you go further I would cut the shoulder hoop (between the front rollbar and the foward seat uprite) and install the inner (sleave) tubing support, Now is the time even tho you might not need it now for the spec, it might happen later or you might go up in class or sell the chassie to sombody esle
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Thanks.
I was going to make a pinoin support down to the cross tube in the bottom. Do you think that is enough?
That reinforcement in the shoulder hoop, isnt that for under 6 sek? Can I take the extra tube and Slice it upp by length ena weld it back together on the shoulder hoop?
Regards.
Palli
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Palli,
tying the front of the third member to the crossmember is acceptable as a pinion support and most were done like that in the past. I usually add tabs to the bottom of the housing and run a K from there to the chassis. As Bruce commented, having a sleeve in the shoulder hoop is a good idea in any case even if it is not required at the performance level that you are predicting as most sanctioning bodies are afflicted by "rule creep" where what was good one year may not be in the future. Are you are talking about cutting a piece of tube lengthwise and shrinking the diameter to make it fit inside the shoulder hoop?
Roo
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I think he was talking about clam-shelling the outer which is not the way to do it. The required sleeve is an internal sleeve. Split the 1 3/8 length wise(it will expand for a tight fit) Split the shoulder hoop, insert sleeve and weld back together and use roset welds to indicate that sleeve is present. I like to to use a 5/8 hole to roset and weld around the perimeter and have the inner sleeve visable.
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I tought it was to be on the outside, it explaines everything to have it on the inside. It is easy to modify it now.
I have a nother question, diagonal tube that goes from corner to corner. Why is it welded to the uprights only? Why not in the corner and welded to both horisonal and vertical tubes.
Borrowed a photo from Clint Jobbs to show you.
Thanks again for good answers, you guys are one step closer makeŽn a 4x4 guy a dragracer :)
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I tought it was to be on the outside, it explaines everything to have it on the inside. It is easy to modify it now.
I have a nother question, diagonal tube that goes from corner to corner. Why is it welded to the uprights only? Why not in the corner and welded to both horisonal and vertical tubes.
Borrowed a photo from Clint Jobbs to show you.
Thanks again for good answers, you guys are one step closer makeŽn a 4x4 guy a dragracer :)
I wonder if the jig that chassis is sitting on is strong enough?
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Its just a quicker way of fitting the diag. If one is fitting corner to corner(the aircraft way)one has to fit an uprite then diag then uprite. If both diag are fitted you will not be able to insert the diag because of its length.
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Ofcourse, then you have to weld in some big holes if you are going to fit the dialog afterwards. Thanks alot, you are helping me a lot.
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When coping the diagonals to fit the uprights, use a piece of 1/4" stock for your offset from the main tubes. Makes the spacing consistant and gives you room to completely weld the tube. Don't forget to drill your gas holes as you go so that you don't blow out your weld.
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Regarding the advice below:
"Also at this time before you go further I would cut the shoulder hoop (between the front rollbar and the foward seat uprite) and install the inner (sleave) tubing support, Now is the time even tho you might not need it now for the spec, it might happen later or you might go up in class or sell the chassie to sombody else."
Current copy of 2.4C seems to agree with the edition you posted the diagram from. I'm a little confused as to the necessity of the interior reinforcement tube as you described.
If I'm reading the spec correctly, the "upper frame rail" is defined as beginning 2" forward of the rear motor plate upright, and extending rearward to the vicintity of the rear end upright and the forward seat upright, at which "shoulder hoop" begins to exist, with step-up maybe required if the two entities are not one and the same, (the larger seat hoop tubing at 1-1/2 x .058).
This would seem to allow the upper frame rail / shoulder hoop to exist as one piece, as it appears to be on PalliP's car, or to consist of as many as many as 4 individual pieces, butt-spliced and sleeved as many as 3 places.
So I don't see why you would want to put a splice there if it's already one continuous piece meeting the spec in the case of the shoulder hoop, and exceeding it in the case of the upper frame rails???
Is there maybe some more advanced spec that would require the splice there
Thanks for any insight,
John Williams
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John,
Bruce's suggestion was not to add a splice as such but to enable the insertion of an inner sleeve to support the front hoop of the cage. I don't have a copy of the SFI 2.6 spec (7.5 and slower) in front of me as I build all of my cars to the 2.2 or 2.4 standard and both of those require the sleeve. As Bruce noted' at his projected performance level and due to where he plans to compete Palli's car may not need the inner reinforcement at this time but rules "creep" is a fact of life and being a step ahead is always a good idea.
Roo
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I inserted the sleeve before bending the lower bends at motor. I pushed it to where I needed it and rose bud welded it in place.It would have been easier to cut ant put in place. On rear where roll bar connects to shoulder hoop I don't think I have to have its since my lower rails turn up and are directly under roll cage bars? Hope I read it correctly that this was ok.Oh yea 6 point cage.
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Couple of points here
With 2.4 only the shoulder hoop needs to be 1 1/2 x .058 2" foward of the rear end uprite and foward of that my step down to 1 3/8 towards the motor plate. The insearction of the 1 3/8 fully into the 1 1/2 to the shoulder hoop bend covers the inner support tube requirment.
The splice between the foward seat uprite and front hoop is for single dia shoulder hoops in that area if its a continous bend. Years prior, one could add another uprite to the foward roll bar hoop down to the shoulder hoop, but this was for older chassies where splicing it at that point would create too much work.
Those that can get the hoops bent in a single piece, have the bends on the same plane, and the front motor plate timed and angled exactly--my hats off to you. I find that by making it 4 piece I can that the rear hoop on my flat and are able to twist the foward sections to center the rear hoop and line up the front half. If one is of on angle or rotation in dealing with long wheelbase chassies, a little bit here makes a huge difference over there
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Dre sez:
"Those that can get the hoops bent in a single piece, have the bends on the same plane, and the front motor plate timed and angled exactly--my hats off to you. I find that by making it 4 piece I can that the rear hoop on my flat and are able to twist the foward sections to center the rear hoop and line up the front half. If one is of on angle or rotation in dealing with long wheelbase chassies, a little bit here makes a huge difference over there
Valuable insight there, thanks. I will bear that in mind If and as I build somethink.
John
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Bruce is correct (as usual). I have access to a high dollar mandrel bender (as well as my in shop unit) so I bend shoulder hoops and top rails in batches. I make the lateral leg of the shoulder hoop long enough that I can make the wide cars that some of my larger customers need for comfort. For the regular one I just shorten the leg. Likewise with the forward portion of the top rail (motor to rear end/cage front hoop). By having some extra length I can trim it to suit where the motor is located. As Bruce notes, being able to rotate that bend at the motor upright sure makes it easier to get the front half of the car aligned. The same applies if you use an arched cross member to mount the steering box. Using two bends and splicing them in the middle allows you to vary the height relative to the frame while still having the bends land on the upper rails. If you want it higher just leave the tail of the bend longer and splice to fit. If it works for Don Long it works for me.
Roo
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Goodie, so what works for Don and Bruce and Kevin, will work for me...
It's awesome that chassis builders like yourselves are willing to share hows and whys, techniques and philosophies.
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Said Kevin, meant Keith.
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It's awesome that chassis builders like yourselves are willing to share hows and whys, techniques and philosophies.
I sure second that! It also applies to engine, fuel systems, and some many other areas. I'm really thankful for everyone out there willing to share knowledge and mentoring novice ones (like me)!