August 19, 2014
After having spent considerable effort to reduce weight on race bikes for the past fourty or fourty five years it gives pause to wonder what madness leads a person to order 210 lbs. of steel ballast to bolt onto a racebike.
We just decided where we can add another 140 lbs. to the nitro bike and 60 lbs. to the long bike. The bikes would be carrying 180 lbs. and 220 lbs. respectively.
Wheelspin is a problem on the salt and magnified as the power and speeds increase. The traction, as I have mentioned before, is very much like that offered by running sheet metal screws in the tires across a frozen lake. Almost 213 mph shows a rear wheel speed of nearly 245. Nick said that the nitro bike accelerated when he eased off the throttle at the end of the run due to wheelspin. The usual allowance for gearing calculations is in the 15% wheelspin range (rear wheel turning 15 mph faster than the actual ground speed). As the frontal air resistance increases with speed that number can grow noticeably.
There are rules that constrain you in where you can apply the ballast. Nothing behind the rear axle is the big one and nothing that reduces the ground clearance behind the seat of the bike to less than 4 inches. The ballast also cannot act as streamlining. With our use of 1” thick steel plate, the streamlining is not nearly the issue it could be.
September 4, 2014
Speaking of ballast, we have just finished the installation of the plates and now there is 260 lbs. of ballast on the bike. This is an increase of about 140 lbs. over the last time out and it is in more advantageous locations. As you can see the rear lower part of the bike is nearly bulletproof, literally.
There were some rules logistics that we had some help from Matt Shuss and Van Butler, both SCTA motorcycle tech experts. As always I am grateful for their help and many year of experience. The good news is that we don’t have to spend hours on the mill removing visually obstructive steel (the blue marks were questionable areas, but they no longer need to be taken out!). There is no bad news, so I guess it’s all good.
The fueler came to life last Friday and there weren’t any leaks in the fuel system. It sounded a little flat, but that is to be expected when you only have 20 degrees of timing in the thing and it wants 45. All in all it smelled great and drove everyone out of the building, exactly the desired result.
Well today we were able to spend a little quality time with the fueler in the driveway and get the barrel valve and throttle body synchronization a bunch closer. It was a bit of a process but it eventually stared to come around. It is a thirsty bugger, using two gallons of fuel while the adjustments were made. The neighbors sort of liked it, though.
Now we are working on the front wheel speed sensor and loading an ignition map into the ECU that plays better with nitro. We will also be able to use the two-step button from the dragstrip to retard the ignition timing in hopes of extending piston life.
Now we are getting to crunch time as the lead time for parts can run into a conflict with leaving, but we will be going through the spares next week with two days set aside to verify and freshen the 749 and 999T parts. There may be more hydraulic cement involved on the 749 stuff as we ran water in the cooling system last time instead of concrete.
We are leaving Saturday morning September 27, arriving on the salt Sunday morning September 28. We then unload, set up, go through tech and if time and energy allows, maybe…..just maybe we will get a run down the salt. If not, Monday morning will be the time. With this expanded schedule, we will have five days to run on the salt, and if you can get it figured out in that time, you just aren’t trying hard enough.
Updates to come.