Dynos and Bikes

[slomobile]

Interested in anything BM has to say about his history working with motorcycles and dynos.

Several of us here are former bikers, more than a few owe our presence here to a tumble off a bike. I'd like to hear about ways to get back on. I've got a 2000 Moto Guzzi Jackal in the garage that hasn't moved in a decade. If I bobbed the rear fender and reworked the seat and pegs I think I could get on it. Some landing gear that drops at stop signs could keep me on.

Dynos, I'm curious how they work. Is it just a big electric motor operating as generator? Or a water brake? Mag brake?

[Burgerman]

Theres many types.
Some like dynojet are just a heavy steel drum. Solid. Its mass is around the same as a motorcycle. So the bike accelerates the drum, and the horsepower is calculated from the torque required to decrease the time on each subsequent revolution. And so draw a power and torque curve. You also need an engine RPM signal to do this. Say from an ingition coil or HT lead. Or you can only plot HP v DRUM rpm.
Because drum and engine RPM should be a constant ration regardless RPMs then you can also detect tyre slipage too. And many other things. To build one you need ACCURATE drum time per revolution. Not RPM. Its not simple. But its pure digital, never needs calibration, and the most repeatable and accurate.

Some have an electric brake. And measure the amount of torque required to hold RPM steady at full throttle, so those use a load cell. The software allows x rpm per second rise to give a full power curve. Useful for configuringfuel and ignition or boost systems. Theres really no other way. Impossible by riding it.

Some have both. So that you can use either. Or both independently. Like my own.

The pure inertial types also measure transmission losses as a negative power curve on run down with the clutch pulled...
So you can measure windage, chain, gearbox losses in each gear etc as well as actual rear wheel horsepower and engine power.
All corrected to standardised temp and pressure so its comparable on different days, different altitudes etc.

A good dyno is accurate to better than 1% even on different days in different locations. Under CONTROLLED conditions.
And a Hardly davidson can almost pull the skin of a rice puddding... Its all about the sound and they have no go. That thing on the right is just the volume knob.


So theres a lot of ways. It all depends what you are trying to do. Water brakes are antiques now.

[slomobile]

Cool.

A few Harley jokes I like:

Why doesn't Harley make computers?
They couldn't find a way to make it leak oil.

Why are Harley parts chrome?
So you can find them on the side of the highway when they rattle off.

hardly able son

[Burgerman]

I once was asked by performance bikes magazine to test an evo 1340. It was about a mile and a half from my mobile dyno at the other end of the airstrip. so I jumped on, THOUGHT that I had pulled away at a low RPM, gently, and then I opened the throttle. Absolutely nothing happend. I was already at full rpm, full power apparently! I needed a recalibration. I thouggh it had cut out or something. So another gear. And same thing. There wasnt anything. It just sort of chugged along. I was amazed at quite how gutless and low reving this thing was. Had spent the best part of 2 weeks testing a bunch of 900, 1000 and 1100cc jap superbikes, ducati 916, etc. on bruntingthorpes 2 mile runway. Those all had 100 hp plus - somtimes a big plus. My own Suzuki WR 1100 had 141 rear wheel corrected horsepower. And a 179mph top speed through the radar trap. Limited only by gearing.

The hardly? It managed 34hp... Out if 1340cc. How is that even possible? I thought it was defective. So tested another one. Which was exactly the same.
It weight about double. And accelerated worse than anything I ever rode. About the same power as you would expect from a lawnmower pulling the heaviest bike I ever rode. It was completely hopeless. Good job it was with that handling and those "brakes"...

My STOCK suzuki ran low 10s at the strip, and 131mph at the 1/4 mile mark before I modified it and in fact with around 80 miles on the clock.
When later turbo charged with a huge rayjay TO4E and nitrous injected that thing had 270hp rear wheel hp, (approx double stock figure) plus the go juice button, another 70 or so on top of that. That went very well!

[slomobile]

That had to be an awesome job.

I never had anything really powerful or fast by todays standards. 1980 Honda Twinstar borrowed from dad to learn on and rebuild. 1979 Suzuki GS1000, 1977 BMW R100S, 1972 Suzuki GT750 water buffalo triple shared with stepdad(I mostly rode bitch), 2000 Ducati ST2, 2000 Moto Guzzi Jackal. I think my favorite was the GS1000 because it fit my body really well and had it throughout high school. Ignition cut out one night, left it in a corporate parking lot and came back 7AM the next morning with truck and it was gone. Stolen legally. The Ducati was the only bike I had that could wheelie on demand, but it had a terrible turning radius and the loud clutch rattle drove me nuts. Maintenance was a pain. It accelerated way faster than engine sound. Made for a weird feeling.

Had a 1962 Pontiac Starchief that used to be moms car. 389, Hydromatic, painted white Imron with pearl, perfect expanses of chrome and red interior. It was beautiful, smooth, huge. Restored it with stepdad. 28k miles in 2001. Sold it to pay the rent and the buyer wrapped it around a pole a week later. 1970 Nova, 1972 Chevy Impala, 77 Pontiac Lemans, 2000 Chevy C2500, 86 S10 Blazer, BlueBird school bus w/navistar 7.3 powerstroke painted black w/red flames converted to camper. Steel porch and BBQ welded to the back. 15 Accord Hybrid, my only new vehicle ever, totaled.
Stepdad had a seafoam green '65 Ford Thunderbird. 390 W block lead sled. Sister has that now. Datsun B2000 pickup I learned to drive a stickshift. 70 something chevy van painted like A team van. Uncle had a Meyers Manx dune buggy and Toyota Cressida. Cousin built a super small but super fast plywood speedboat to run on a tiny lake. Grandpa passed on his 1929 14' Alumacraft fishing boat which he used to run Canadian Whiskey during prohibition. I found a 1962 Scorpion snowmobile in the woods stripped of near everything. I put an Evinrude motor and random track on it one winter and my brother wrecked it the next. We had the rusting shell of some unknown truck in the woods behind the house we would sit in and pretend. 1920s-1930s probably. Super small cab compared to todays trucks.

Lots of vehicle memories. Now only the Guzzi, Promaster Van, and '08 Honda Pilot remain.

[Burgerman]

The Ducati was the only bike I had that could wheelie on demand,

Most of my bikes were double overhead cam, 16 valve 4 cylinder 1100cc 120 to 156bhp as stock. I never liked smaller bikes. All of them wheelied on power in low gears. Some did it in second. Second is about 100mph plus on a big superbike.

Once you turbocharge and / or nitrous inject them and do a few other mods then they wheelie in quite literally every gear. So to accelerate fast you need to drop the front, (fork legs through yokes) and reduce travel. On the rear you need a longer swing arm - amount depends on track.

Then they still wheelie like crazy in low gears and so you increase gearing so that 1st gear is good to around 90 to 100 and the reast are geared for around 200 because with a bug turbo, and say 25lb boost you are looking at 300 plus horseower at the back wheel. At the strip. On the street you set boost a bit lower like 17psi boost for reliability. That means you still get accidental wheelies in the first 4 gears. And up to around 14 to 150mph... Or you can smoke the tyre for about 1/4 of a mile insted. Depends if you hit it hard at low speed or wait for it to lift!

Anyway thats all a bit mentalist. The turbo bikes have silly power. But with a huge turbo you get a lot of lag. To get rid of ALL of the lag, you use nitrous. Around 45bhp worth, or 70 extra on the track, works unbelievable well. You get full boost instantly. Obvously its not actually instant, but the nitrous makes instant power before the boost then ramps up super fast because of the extra exhaust gas. It just feels like you lit the blue touch paper.

Anyway, theres a stock 1980s (1984?) VFR 750 on there. It isnt mine. It belonged to my freind when we were "touring" spain... It was good for about 155mph which wasnt bad for a little 750 in those days. See pictures. Its here.
https://www.wheelchairdriver.com/board/ ... 52#p203965

That picture was my freind fotographing the clocks while I was alongside watching this happen at around 155. He did it no handed to hold the camera still. So it was slowing down rapidly on closed throttle as he did so.
Even so 152 mph approx on the clock in the early 80s from a stock 750 isnt too bad! It couldnt match my 1100cc bikes though. No the VFR 750 didnt wheelie well. Well at least HE didnt! It wasnt quite powerful enough to do it at every opportunity. Wheeliing was my party trick. I used to do it for miles on end in many gears. And out of lights, overtaking cars, etc. Learned while drag racing silly overpowered drag bikes and speed testing everything on a 2 mile runway while working for Performance Bikes Magazine. Loads of practice every week. Once learned, its easy. And hard not to just do it all the time! It just feels good at speed for long distances as you change gears accelerate and steer and pass cars etc.

[slomobile]

Was thinking about how to turn the Guzzi into a trike that leans, but keeps the rear car wheels flat on the road. Came up with something like a De Dion suspension, but inverted. Then realized I never actually knew what a De Dion was so found this little outing. Looks like fun.
https://youtu.be/BpvKYuT7iFc?si=fnzJAULPtj1ALZ1m

[Burgerman]

Those look dangerous.