Dirt track frames

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Dirt track frames

Postby airhead Troy » Mon Jan 03, 2011 10:36 pm

Why don't more people us a dirt track frame for road racing? Geometry? Strength? I'm just wondering is it possible?
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Re: Dirt track frames

Postby Steve 976 » Mon Jan 03, 2011 11:35 pm

I am building a xs 650 for next year that is using a Schwerma (Champion) frame. Framecrafters did a lot of bracing to it to make it ready for road racing. From what I have been told, a dirt track frame is not stiff enough to road race without some bracing. We will see how it goes....
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Re: Dirt track frames

Postby airhead Troy » Mon Jan 03, 2011 11:52 pm

Bracing near the head stock to the swing arm pivot?
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Re: Dirt track frames

Postby phantom309 » Tue Jan 04, 2011 12:19 am

Troy , some guys can make them work fine but I had a trackmaster that was bad no matter what i did to it. Flexed so bad it would snap back coming off a corner.Got it better but never as good as a stock t140 frame.
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Re: Dirt track frames

Postby carl849 » Tue Jan 04, 2011 9:50 am

I use a period Trackmaster frame on my Yamaha 175 in 200GP, and it does flex. But on such a small bike it's tolerable. Double the torque and it would probably mean big trouble.
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Re: Dirt track frames

Postby T.Read » Tue Jan 04, 2011 10:15 am

I raced one of Tom Sharp's in Sportsman last year a couple of times. It handled corners really well, as in turning with the steeper rake. But it vibrated like hell and was a handful to hold on to. T140 frame was much smoother and easier to handle. The stock frame bike he has had a few degrees taken out of the steering head and it turned almost as good as the Trackmaster. It wasn't as steep. I could really tell a difference in that aspect between my stock rake, braced T140 frame compared to the de-raked stock frame and Trackmaster. Mine has a lot more chatter in some turns(I think mainly due to poor fork setup), the Trackmaster had a shit load of chatter in turns 2-3 at Barber...not as much elsewhere, just the long sweeper turns where you're on the side for a while. The stock de-raked one had very little. I got mine to stop most of it in those turns at Barber, but as I went faster, it would do it in other turns. Didn't notice the Trackmaster flexing much, but I think Tom had them brace it, it's a hybrid Star/Master with a braced swingarm and I think had the brace from the backbone to the rear diagonal tubes. Also, I don't think I was going fast enough to tell any flex. :mrgreen:

Hope that helps.
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Re: Dirt track frames

Postby limy_1 » Tue Jan 04, 2011 5:04 pm

Remember David Temple?
I believe he raced a trackmaster frame in the sportsman 750.
I don't know how it did in corners but you could see something flexing on the starts.
I just don't know if it was the bike or his riding style to get out front?
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Re: Dirt track frames

Postby carl849 » Tue Jan 04, 2011 6:01 pm

Under hard cornering mine will flex enough to make the swingarm rub the back of the footpeg bracket.
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Re: Dirt track frames

Postby Steve 976 » Tue Jan 04, 2011 6:46 pm

Framecrafters have had to do so much bracing on this frame it hardly resembles itself. They gusseted everything and made "tie rods" that tie the swingarm pivot to the steering neck. The rods are removable to service and remove the engine. It does have a steep steering angle. Should be fun to play on...
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Re: Dirt track frames

Postby ChuckS » Wed Jan 05, 2011 10:41 am

Steve, do you have to remove the engine to change the spark plugs? :mrgreen:

(ducking, running)
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Re: Dirt track frames

Postby spargo19 » Wed Jan 05, 2011 11:26 am

John Ellis' old 750 Yamaha used to buck and wobble like crazy - he rode it like a dirt track bike (So did Temple, for that matter). Definately a different way of going fast.
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Re: Dirt track frames

Postby Junk Yard Dawg » Wed Jan 05, 2011 12:08 pm

Had a Champion XS750 Yamaha in the 90's , won 4 championships with it. It bucked, slid, wound up, but was very good tool at the time. Had to alter my style to DT mode. Was a great bike , but hard on tires as I remember. Light, and if you got in trouble, always seemed to recover. I think it scared others more tham me, as I did not know any better. Had some great times with that bike. Sold it to Rodney Blanchard in La. I had a better swingarm made, larger axles, and experimented with different top engine mounts. I would not be affraid to build another, but would have Framecrafters do a swingarm, larger swingarm pivot mod, brace the neck some more , and go have some fun.

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Re: Dirt track frames

Postby Steve 976 » Wed Jan 05, 2011 10:24 pm

ChuckS wrote:Steve, do you have to remove the engine to change the spark plugs? :mrgreen:

(ducking, running)


It's not a Ford truck :)

I dunno, just finished the motor...hopefully I can remember how that jigsaw puzzle goes back together.
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Re: Dirt track frames

Postby Jamie Linxwiler » Mon Jan 24, 2011 1:23 am

Here, I will wade into this, nobody has replied in a while, and the other topics are stale.

My thought is, depends on what dirt track frame you use, whether it works well on asphalt or not.

And I think this is worth figuring out, because dirt trackers on asphalt are real fun. I think it was a picture of Snuffy Smith on his Triumph Trackmaster at Road Atlanta in some magazine that got me into AHRMA racing to start with, and I never really considered any class but 750 Sportsman where you could basically race a dirt tracker on asphalt.

I have ridden dirt track frames on road race courses a fair amount over the years, I rode a period, original dirt track Redline 750 Triumph 1992-3 through 2001, and put a modern C&J copy of a Champion under it for another 5 years or so. The Redline frame was not so good, the Champion, thumbs up. In fact, it is up on my stand now being worked on, and I am going to bring it out this year.

I certainly remember the Yamahas David Temple and Johnny Ellis rode, man, David getting a bad start at Sears maybe 95-6? then passing a clump of us on the first lap on the inside under the white line in turn 5, the right before the Carousel, slithering and swapping the whole way, phew, how could I forget that? Johnny's always looked a handful too, but also really fast (I think it was all pilot for both these guys).

Anyway, for asphalt there are dirt track frames, and there are dirt track frames, and not all of them work for this application. Trackmasters, and I hope I don't offend anyone here, aren't necessarily the tip, especially for 750's (interesting Carl has the same problem on his 200), they are real flexible, in fact made to be flexible, the center backbone is not well tied to the tubes from the pivot area to the seat, there are no up tubes connecting the outside of the s/a pivot forward to the back bone, the outside of the swingarm isn't located well, and the pivot bolt and bearings are small, and the flat wheel plates on the swingarm flex too, and the motor mount plates are long and flexible, and not tied to the swingarm pivot directly. Great for dirt track, not so rigid for asphalt. I had a Trackmaster 750 Triumph dirt tracker and it wiggled a fair amount on dirt, couldn't imagine it on asphalt. Funny, true story--first time I met Arty Stapleton, who runs a 750 Trackmaster, at Savannah 1993, his rider Duane Veeder (national number 99 dirt tracker) was parked in the grass outside turn 4, the left at the head of the pits, and he just sat there the rest of the race, didn't get off the bike or move. Later he said it was pumping and swapping so hard after hitting the bumps that used to be on the apex (before it was repaved) he was glad to get it out in the dirt where he knew what to do with it. But Arty's bike has had some real good results, it all depends on the pilot.

My period Redline had the same flex problems. While the Redline had a stiffer Champion style full cradle frame design that held the outside of the s/a pivot, it still had flat axle plates and a little swingarm bolt and s/a bushings, and little thinwall 7/8 tubing and little flexible triple clamps. It flexed a lot, a handful, hard to know where it was going next, but really, really fun. Lively, say.

All I can add to this thread is I changed from the Redline to a modern (NOT period) C&J reproduction of a Champion some years ago, and it is dead steady. The Triumph cases mount outboard in the rear (that allows the rear motor mounts to be two little 2 inch C shaped chromoly plates that mount like big flat washers under the nuts on the swingarm axle and directly to the motormount bosses on the engine cases so the engine pushes directly on the s/a pivot)-- and with the engine so solidly tied in the frame there, and the bottom, and the front, and in a real stout top motor mount, it stiffens things up considerably. The swingarm bolt is big diameter, held in the frame in two boxed plates on each side, with enough diameter in the pivot tube to leave room for a stout spacer between the bearings, so you can tighten it all up, and it pivots in needle bearings. This C&J version of the Champion also has the engine loop and the seat loop made from 1 inch chromoly, not 7/8, so it is quite a bit stiffer, it has a 3/4 chromoly rear axle with outrigger bearings (4 total bearings) and a 1x2 inch chromoly swingarm with sliding axle blocks full width at the axle, and it has 38mm Marzocchis with full thickness Ducati triple clamps too.

So I go slow, and I am getting slower as I get older, but this is a very stable, comfortable dirt tracker to ride on asphalt--it's a lot better than I am. It's all in what you use for a dirt track frame--C&J made this one more like a modern dirt tracker, with a lot more stiffness built in. FWIW.
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Re: Dirt track frames

Postby T.Read » Mon Jan 24, 2011 11:19 am

That sounds pretty nice Jamie, where you going to try bringing it out to this year? Anywhere in the east? I'd like to get a look at that.
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Re: Dirt track frames

Postby phantom309 » Mon Jan 24, 2011 9:45 pm

mine came off the scales at 290 thith gas and oil.Its only going to see the dirt unless we run it in the rain someplace.:-)
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Re: Dirt track frames

Postby limy_1 » Wed Jan 26, 2011 12:45 pm

phantom309 wrote:mine came off the scales at 290 thith gas and oil.Its only going to see the dirt unless we run it in the rain someplace.:-)


So you are going to bring that bike to all the races just in case right?
Just like washing the car it will rain or is that if you bring it you won't need it? :lol:
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Re: Dirt track frames

Postby Michael Moore » Fri Feb 11, 2011 1:13 am

The Kenny Roberts DT frame I used on my TT500-engined roadracer worked very well for me and some AFM fast guys who rode it also liked it.

cheers,
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Re: Dirt track frames

Postby cweeks » Fri Feb 11, 2011 1:55 pm

My XS750 750 Sportsman bike uses a C&J frame that Jeff (of C&J) braced. The steering head, swing arm pivot and swing arm itself were braced. This was coupled with taking the bike to GMD and they first ensured the frame was absolutely square and then gave me the necessary figures so I could source new triple clamps (with revised geometry for a bit more trail) and slightly longer Works shocks to make the finished product comply with their "sweet numbers."
It did not feel stable prior to adding the bracing and visit to GMD, and I confess I rode is more slowly because of that. But, hey, it looked cool.
However, I have no excuses any longer. Now I can, e.g. enter and go through T8 at Willow wide open with no flexing, weaving or "hunting" for traction. Instability during braking and chattering are also gone. Even hitting bumps when leaned over don't upset it. And, less weight is always good. Like Tim's it weighs about 290 - 300 with fluids but no fuel.
Glad to hear Jamie is bringing his Triumph out this year. It's a beautiful bike.
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Re: Dirt track frames

Postby RDTZGUY22 » Sun Mar 06, 2011 2:33 am

We have had good experiences with both large and small displacement Trackmaster set-ups in roadracing. Mike D. has won sportsman 750 several years in a row on our Trackmaster replica. However, we box in the swingarm pivot plates and use different neck gussets, so not an exact replica ... We consider the Champion as being less suited than Trackmaster for roadracing, hence suggesting to Steve to brace from neck to swingarm pivot. Im not denying the Trackmaster couldnt benefit from the same mod but "off the shelf".......Trackmaster.

As for other DT frames in roadracing, I couldnt say. I havent had first hand experience with any others but I would imagine most of them suffer from the same flaws.
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