Landracing Forum
Tech Information => Technical Discussion => Topic started by: Calkins on February 11, 2015, 01:44:09 PM
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Be fore I start ordering chromoly, I need to figure a few things out. Without Willie (God Speed) here to yell at me, I am lost. I am basically building a version of late '60's Hagon drag bike. Those bikes had an open cradle, as in the engine is the lower frame. I have many questions...
* Ideal, or minimum tubing diameter and thickness.
* Minimum steering angle.
* Recommended minimum wheelbase.
I am planning to go for A/G 1000, with APS/G 1000 in the future. There is a possibility that SC/G 1000 may need to be tried as well.
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1.25 inch Dia. DOM (no Moly... don't need it) 0.85 Wall.............27 to 30 degrees steering head angle...... 61 inch whl. base....build it strong, if you plan on a sidecar later..........................................................................
If you don't plan on a sidecar use 1 inch dia.
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Bak --- we agree --- For a 2 wheeler use 1" DOM ... Not moly.
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I am fine with MS. But 1" for a stressed frame? For a 200mph bike?
I attached a photo of the pro Triumph flat tracker that I have worked on. He used 1.5" CM for the main frame, with 1" and .75" for the rest. His frame uses the engine as a stressed member as well.
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Not many land speed bike using single tube.
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There is world of diff.................regarding stress on a flat track frame ,then a LSR straight line chassis.......
I am certain Alf did not use CM........and I am almost certain the frame was sif. bronze welded......
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When I am back on a computer tomorrow morning, I will upload the article about those bikes. I posted it on the General Chat section a while back. I am pretty sure Alf used chromoly on that bike back in 1966.
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Using the motor as a stressed member requires that that the motor be rigidly attached to the frame in at least 3 places (head steady doesn't count) and that all mounting points (bolts) be torqued correctly and kept tight (check them often). Otherwise, your top tube will be doing all the work and will very likely fail. The "grass track" frame shown in your first photo appears to have a hinge in its lower connection which would eliminate its function as a stressed member.
If you're using a straight single top tube, be aware that compared to 1" x 1/8" wall, 1-1/4" x 1/8" wall will be twice as strong against buckling and 70% stronger against bending. Furthermore, 1-1/2" x 1/8" wall will be four times as strong against buckling and 2.7 times stronger against bending than the 1". Don't skimp as the weight penalty is minimal.
If you're using curved tubing for the top member, it becomes more difficult to analyze as all members will be subjected to bending. Also realize stresses will be approximately proportional to the square of the length of that member. Therefore, doubling the length of a member will increases bending or buckling stresses by a factor of four.
I am a mechanical engineer, but not a structural engineer so I won't try to give you any specific advice.
Tom
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I think the "pivot" that you are talking about is the front engine mount. This frame was built for a pre-unit Triumph twin.
Here is the Cycle World article from October 1966. They say that the backbone is 2" tubing and wheelbase is 57.8".
Also, my modern Triumph twin has mounting lugs on the front and rear of the cylinder head, one on the front of the crankcase, and two on the rear. It also has a swingarm pivot that could be used for mounting. My frame will be a hardtail, by the way.
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In the article you posted, I can see that front mounting plate is connected rigidly to the motor to prevent it rotating. In short, if the motor can up or down or sideways, it is not rigidly mounted. From what you're saying, it sounds like you have several connection points that should be able to allow the use of the motor as a rigid connection. Anybody except an engineer can give you advice and assure you that the design will work, but an engineer is liable if he or she gives you advice, or doesn't caution you when they should, and will therefore be reluctant to offer advice.
Tom
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What motor will you be using?.
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Modern air cooled Triumph 865cc twin, with the 270* crank. America, Scrambler, and Speedmaster had these engines. Bonneville and Thruxton have the 360* crank. My engine came out of an '05 Speedmaster.
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How much horsepower do you anticipate getting from your Triumph?
Joe
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About half of what I need. The stock engines were rated at 52hp, I believe. The 995cc flat track engine, with 44mm carbs and 38mm restrictors, had 95hp or so. I would guess I am going to be lucky to hit 120hp.
A side note, the liquid cooled and fuel injected '06 Triumph Daytona 955i was factory rated at 149hp.
Will my air cooled engine be lighter than the 955i engine? Probably not. Will I match the hp of the stock 955i? Probably not. I keep trying to stop wanting to build this bike. I do not think I will be anywhere near to target speeds.
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http://www.hermys.com/triumph/speedmaster/2005/ (http://www.hermys.com/triumph/speedmaster/2005/)
(http://www.hermys.com/downloads/2005/SPEEDMASTER_09.jpg)
(http://www.hermys.com/downloads/2005/SPEEDMASTER_07.jpg)
(http://www.hermys.com/downloads/2005/SPEEDMASTER_08.jpg)
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WHY....OH ....WHY....do you want to copy a 1960's frame, are you racing in the "Vintage" Class......these are modern times, copy a chassis from the present day, that is build to hold present day horsepower.....if Alf had 100hp (even on Nitro) he was doing good........