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Post by Sticks on Jan 19, 2009 8:02:22 GMT -6
Took a couple of the old rupps to the radar runs down in Nicollet Minnesota yesterday one was a 73-340 nitro and the other one was the little 23 sprint. anyway everyone there was complaining about the radar gun being off about 4 miles per hour on the slow side.
the 340 was running at 55mph and the 23 sprint was running 36mph I was wondering what you guys think. do these speeds sound like there in the ball park for these stock sleds?
Anyway Isaac and Caleb had a great time. Isaac took 1st in the 0 - 350 class and Caleb took 3rd in the 0 - 400 class and that a really big deal for two kids at the age of 10 and 11 where going out again next weekend and I have all week to work on them. What do you think taller gears?
Sticks
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Post by wigman25 on Jan 19, 2009 9:42:19 GMT -6
Hey Sticks: Your sleds seem to be running in the general range of where they would normally run. You didn't say how long the run was, but in general the easiest way to gain speed is make sure you are using a good synthetic oil to help with the power output and loosen the track up just to the point that it won't skip. The chain tension should be checked to make sure it isn't over-tight or too loose. Also, make sure everything is lined up real good including the track and the clutches - a basic 'chassis blueprint' so to speak. Don't know if those engines will respond well to gearing them up, I think they were just about maxed out right from the factory. Making everything turn nice and easy is absolutely the quickest and easiest way to gain horsepower to the track and top speed - remember, friction eats up a hugechunk of horsepower! When setting a sled up for speed, reducing friction is job #1. Clutching comes next. If you are out of whack, you could easily gain several mph by getting things working right. Good luck next week!! Wig
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Post by wigman25 on Jan 19, 2009 10:00:21 GMT -6
One more thing - this little guy ran 38mph at a radar run in MN last week, so your Sprint is right on target. You might be able to get 40mph out of that old girl yet!!  |
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Post by nitrofa340 on Jan 19, 2009 10:35:33 GMT -6
Nice to hear other guys are out racing thier Rupps in the Twin City/Minnesota area. Good job.
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Post by Sticks on Jan 19, 2009 16:20:45 GMT -6
Don't know where you got the picture, But thats my sled from the nicollet run yesterday. I guess I didn't see the run at 38 mph on the sprint. I was to busy taking care of all the kids on the nitro and my AC Sno Pro
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Post by wigman25 on Jan 19, 2009 17:08:41 GMT -6
That's funny - I got the pic from over on the VintageSleds.com site, it didn't say who took the picture or who was on the sled. That's a real nice sled you have there!! Glad you have the kids involved, it must be a blast.  Wig |
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Post by Sticks on Jan 19, 2009 17:28:01 GMT -6
Hey Wig, where on the site is it located? The kids want to see it. Thanks Sticks
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Post by wigman25 on Jan 19, 2009 21:17:20 GMT -6
Is this your Nitro in the background??  The pics are in the Vintage Sleds 24/7 Only section of the board, thread title "Some pics of our local speed run" Wig |
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Post by Sticks on Jan 19, 2009 21:28:38 GMT -6
My nephew is on the sno jet, My son Isaac is on the nitro, My son Caleb is on the Sno Pro next to the nitro, The girl in the pink next to the jet is my neice on one of my old sleds, And the guy in the green is my nephew, he tied for 2nd w/the sno pro.
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Post by Sticks on Jan 20, 2009 20:10:06 GMT -6
Looking around the shop today for some taller gears and turns out there all the same, 14-28s is all I have. Anybody have a 15 or a 29?
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Post by onlyhere4themoney on Jan 20, 2009 20:35:04 GMT -6
I might I will have to dig around and look.
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Post by nitrofa340 on Jan 21, 2009 8:56:28 GMT -6
Looking around the shop today for some taller gears and turns out there all the same, 14-28s is all I have. Anybody have a 15 or a 29? The problem isnt your gears. If you are spinning 7250 rpm with 14/28 gears using a 6.05 driver you are geared for 65.24 mph. It appears you are not fully shifting out with the gears you currently are using. Adding more gear is not the answer. |
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Post by wigman25 on Jan 21, 2009 9:20:06 GMT -6
Thinking about that - make sure your belt is the right size as well, if it is too wide it won't go all the way down into the secondary no matter how hard you pull it. Believe it or not, even though it is dangerous some guys even used to use worn belts or sand a new belt down on a belt sander so they squeeked that extra little bit out of the top end, sometimes they would jam down inside the secondary and lock everything up!! Had to cut them out with a knife to get going again!  Wig |
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Post by nitrofa340 on Jan 21, 2009 20:34:38 GMT -6
Thinking about that - make sure your belt is the right size as well, if it is too wide it won't go all the way down into the secondary no matter how hard you pull it. Believe it or not, even though it is dangerous some guys even used to use worn belts or sand a new belt down on a belt sander so they squeeked that extra little bit out of the top end, sometimes they would jam down inside the secondary and lock everything up!! Had to cut them out with a knife to get going again! Wig That is some cool information Wig,.......I have had the exact opposite experience. I have always gone FASTER with a new, wide belt. I always assumes it was because a new belt of the proper width fit the primary clutch correctly, and came all the way to the top of the primary upon full shift out. I could be wrong, however. |
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Post by Sticks on Jan 21, 2009 20:45:13 GMT -6
I took the sled out for a spin on the road in front of my house today and its running about 7300 rpm it feels strong, the clutchs all seem to be working. The speedo for what is worth is at 68(we know that's not right) I can hold it wide open and there seems to be room for a taller gear. maybe I'm wrong. Has any one else gotten a radar speed with there 340 nitro?
And is 6.05 the right figure for a stock nitro drive?
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Post by nitrofa340 on Jan 21, 2009 20:52:11 GMT -6
Pssstt,.........hey Rick. Go out in your garage and grab a '73 driver and measure it.
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Post by wigman25 on Jan 21, 2009 21:05:00 GMT -6
Thinking about that - make sure your belt is the right size as well, if it is too wide it won't go all the way down into the secondary no matter how hard you pull it. Believe it or not, even though it is dangerous some guys even used to use worn belts or sand a new belt down on a belt sander so they squeaked that extra little bit out of the top end, sometimes they would jam down inside the secondary and lock everything up!! Had to cut them out with a knife to get going again! Wig That is some cool information Wig,.......I have had the exact opposite experience. I have always gone FASTER with a new, wide belt. I always assumed it was because a new belt of the proper width fit the primary clutch correctly, and came all the way to the top of the primary upon full shift out. I could be wrong, however. You have a point, I imagine in some circumstances it could work either way - a wide belt is certainly going to push the secondary open all the way, increase clutch pressure on the belt, and being brand new it would grab a lot better on a smooth clutch face. But it won't go down into the secondary as far, they will only open up so far without mods. But - your best drive ratio is realized if the belt was narrow enough so that the primary just holds onto the belt on the outer edge by squeezing the primary to bottom out and the belt goes way down into the secondary just shy of the point of no return, it basically gives you a slight overdrive rather than the standard 1:1 top end ratio. Food for thought.  Wig |
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Post by rupprat on Jan 21, 2009 21:10:21 GMT -6
Pssstt,.........hey Rick. Go out in your garage and grab a '73 driver and measure it. '72 and '73 are not the same. '72 is a 10 tooth cog approx. 6 1/8" dia. '73 is an 11 tooth cog approx. 6 5/8" dia. |
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Post by Ruppsforever on Jan 21, 2009 21:16:55 GMT -6
Pssstt,.........hey Rick. Go out in your garage and grab a '73 driver and measure it. '72 and '73 are not the same. '72 is a 10 tooth cog approx. 6 1/8" dia. '73 is an 11 tooth cog approx. 6 5/8" dia. So running a sled with the 73 drivers has way less stud clearance than the 72 drivers. Great info !! |
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Post by nitrofa340 on Jan 21, 2009 22:28:56 GMT -6
I could be wrong on this issue, I frequently am. I am by no means an expert on the early models. But from what I have read and heard, the '72 and 73s used the same front drivers from the factory. A few years later the smaller drivers were no longer available from Rupp and you were instucted to install the rear idler drivers onto the front drive shaft. That is how many '73 sleds ended up with bigger front drivers. Anyone else heard this?
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Wig
Wig
