Building a race bike

[Dellortoman]

Transmission and crankshaft lie horizontally in one plane. If the transmission gear wheels touched the oil, the crankshaft would, because of the greater OD, foam up the oil - or am I thinking wrong here?

Where actually is Cam? His analytical skills are sorely missed right now ...

Yes, I think you're thinking wrong.
No analysis required. I don't know much about the 750 twins, but normal motorcycle design is to have the rotating parts clear of the oil.

Edit: I just noticed that Piet answered that question comprehensively. I should have read the whole thread before responding.

 

[julian]

Sid a bit more welding last night,
Almost finished.

I will not be grinding the welds down as this is a big mistake, I do not want this to crack and mess up during a race.
As I said before, TIG welds can be brittle so I have made them as strong as possible with 100% penetration so should be perfect in this application.
3mm 6061-T6 and thick full tube supports for the locating bolts. Quite happy with it but may still possibly weld on some side fins but think I would only manage 3 so may not really be worth the effort. We will see tomorrow.

Edit
Will be making side fins, there is room so will draw them up and have some cut this week. Think they will look cool as well as cool.
J

 

[julian]

Little update,
Exhaust manifolds and collector mocked up under the sub sump. 120mm ground clearance and no chance of grinding in turns as the engine cases hit well before the sub sump even gets close.
Exhaust is calculated to be at optimal length and dia (45mm id) for a very good power curve and a power band from 6000 rpm to 12000rpm and actually still fairly usable bellow that with a smooth transition of power if the theory works.
Cyl head going away for computer modelling in the coming weeks and then machining out, welding and CNC machining to the current design.
New pistons ordered yesterday with a 3mm very gentle dome to give me 13.5:1 CR

Just got a load of bits to do some rocker mock builds in the mean time before deciding on the exact shape and form for these to be machined in 7075-T6 ally. Roller followers and Roller tips. All including the pivot bearing with needle rollers.

 

[Vince]

I seem to remember race fuel, big compression.

 

[Laverdalothar]

Little update,
Exhaust manifolds and collector mocked up under the sub sump. 120mm ground clearance and no chance of grinding in turns as the engine cases hit well before the sub sump even gets close....

That looks already pretty fast while standing still! Very nice... Personally, I do not like the way the 750 SFC fairing generally is mounted, it just looks wrong to me (I know it is similar to the original ones on yours, I just prefer the underside of a fairing to be in line with the underside of the tank).

 

[julian]

I do know what you mean Lothar, I did look to see if I could adjust it's positioning to be in line more but it took the screen either too far away from the rider looking wrong, or / and the light (air duct in my case) too low in order to have it right for the steering.
I was thinking of another fairing but the rules quite strongly specify that in my class you can only have the fairing that was fitted in period and I really do not want to give anyone any ammo to get me disqualified or prevented from racing. My intention is to take the goal posts so far up the field that no one will know what has hit them, but that will cause a lot of whingeing and whining anyway so I really don't want to give anyone ammunition and need to tread very carefully just on the right side of the rules.
I like parallel lines and nice alignments etc so had to bite my lip a little and fit it where it was ergonomically and mechanically most useful.

Regards,
Julian

Vince, Methanol or possibly 50/50 Methanol/98 so 13.5:1 is not that big a number.

 

[Vince]

I was going to say Dope but I was sure about compliance for your racing class, the older Pommy bikes use it here and Castrol R as well but I don't know how the Oz regs specify its use, I have heard 15 and 16/1 and that amazed me. Main jets like drain pipes.

 

[piranha-bro2]

If you want more leeway for positioning Julian the Duke SS fairings are very similar - but not sure when the first Imola race bike appeared. '72, same as the SFC? I gave up on the SFC fairing for my project because the steering/handlebar area was just too restrictive.

 

[piranha-bro2]

Oh, and really looking forward to more news and pics on the head, the rockers and any other stuff in the pipeline.

What happens after the 45mm collector, Julian? Will you have to design something to keep decibels down or is the class immune due to the simple issue of the era you're representing? And if this beast goes as the modelling indicates there are going to be some jaws dropping in the class you're competing in!! (and very pissed off owners )

 

[julian]

Hi,
Am quite happy with the fairing as it is now, plenty of room for hands and handlebars, enough room for the oil cooler air duct etc and the steering damper in there also. It seems quite comfy for elbows and arms also.

Although I don't think there would be an issue with using another type of fairing, I would rather stick with a traditional SFC type and have come to terms with it now.

Vince.
I have tested CRs up to 15:1 in cars with methanol but found only tiny improvements above 13.5:1 and only then "IF" you can keep the crown flat which I would not be able to if I went higher than 13.5:1 and if I did that a 50/50 may not be high enough octane and I may need that for longer races fuel economy issues. Will see.

 

[julian]

Oh, and really looking forward to more news and pics on the head, the rockers and any other stuff in the pipeline.

What happens after the 45mm collector, Julian? Will you have to design something to keep decibels down or is the class immune due to the simple issue of the era you're representing? And if this beast goes as the modelling indicates there are going to be some jaws dropping in the class you're competing in!! (and very pissed off owners )

Hi,
I have what is called a "Merge collector" this is two pipes collecting into one, with a slow taper and a reduction to 50mm diameter, from there it has a quite strong taper from 50 to 65mm in about 30mm length, to give a very strong return pulse. Then I have a tapering secondary from 65mm to 76mm over roughly an 800mm length. This goes up between swing arm and rear tyre and out through the side in a sort of "S" shape. I will build / design a muffler on this in such a way that it does not effect the signal back down the pipe. Will need some experimenting but have done similar things before that have worked well and with little measurable power loss and a good reduction in noise. There is room for a mufler if needed.
I will need to hear what I have though as the cam timing massively effects exhaust noise and on this engine I have an exhaust that opens very early so could end up being rather noisy. Will see.

Rockers at the moment are just going to be mockups made in steel plate etc as there is a lot of funny quirks with roller cams and especially with the contact points I need to use. I don't have a decent dynamic cad system at the moment so will need to hand model it all. Will post pics soon.
J

 

[Paul Marx]

If you want more leeway for positioning Julian the Duke SS fairings are very similar - but not sure when the first Imola race bike appeared. '72, same as the SFC? I gave up on the SFC fairing for my project because the steering/handlebar area was just too restrictive.

SFC per se appeared in the spring of 71.

Paul

 

[GregT]

I note your experiences with methanol in cars. My experience with water cooled cars and bikes is that you have to keep the water temp at around 70 deg C to get good combustion. Once you have a thermostat setup working then you work out the hottest plug you can use safely. It's a bit contra intuitive but it works.
If you do want or need a economy run fuel - a race where you don't have enough tankage for example - try 80% methanol, 20% tolulene. Ford used it in the pushrod engines at Indy to save one fuel stop in the usual 5. You can run it with rich petrol jets and needles. Really nice to set up for - but it's probably carcinogenic. Ford's published figure say down 2% HP on straight meth with both optimised. But 20% better mileage.

 

[julian]

Hi Greg,

Absolutely, Normally when ever I run Methanol I use 10% Toluene 90% Methanol, it is amazing how much it helps starting and general combustion. Allows us to run a much smaller advance in the ignition also and really helps in the high RPM areas. We did not measure any noticeable power changes + - a couple of hp and nothing constant, but over 8000 rpm we could measure good gains on every engine we tested (old engines with generally poor combustion chamber shape etc so probably needing help)
For sure where the rules allow I will run Toluene as a mixer. But "as the rules allow" is the big word here.
On the cars we run here on 50/50 it is actually 50% Methanol, 40% 98 unleaded, 10% Toluene.
Good stuff when it burns but not nice to handle.

Regards,
J

 

[Vince]

When unleaded fuel became mandatory here in NSW there was a big scandal involving the Adition Of Toluren to dilute the fuel at privately owned Fuel Stations to save the stations costs and illegal The Weights and Measured bunch, Government Agency did spot checks and discovered this.

 

[julian]

I think the issue there is twofold.
A. Toluene is a carcinogen and not nice.
B. It is usually sold as a solvent used in the paint industry and Dry cleaning and therefore not taxed at the same rate as fuel.

Probably not going to go down too well with the inland revenue!
One thing I know for sure is not to mess with the IR. You will loose!

J

 

[helicopterjim]

I used to burn toluene in my lawnmower as I could get it free from work. Then I tried running alcohol for fun but I had to remove the mainjet completely and also remove the engine shroud as the motor needed to get really hot. Removed the governor so it revved as high as possible.
I never thought of mixing the two.
I also acid etched the lawnmower blade so it was deadly sharp. I could run as fast as I wanted and still cut clean.

Jim

 

[1200 JOTA]

I used to burn toluene in my lawnmower as I could get it free from work. Then I tried running alcohol for fun but I had to remove the mainjet completely and also remove the engine shroud as the motor needed to get really hot. Removed the governor so it revved as high as possible.
I never thought of mixing the two.
I also acid etched the lawnmower blade so it was deadly sharp. I could run as fast as I wanted and still cut clean.

Jim

I used to enjoy that US TV show with Tim ? ... it's based on Jim's real-life!

 

[redax5]

used to use Powerplus 105 in our race engines for the first 4 seasons of racing but constantly went through fuel tanks no matter what tank liner we tried, went through 9 tanks in those 4 seasons. Even carried a spare tank to the race meetings with us
Tried one of the Aussie made tank liners and it did not work either so asked them some tech questions about what was going on, one of their chief technicians asked me what fuel and looked into it, he came back and told me one of the products that Powerplus were using to gain the extra octane rating was basically paint stripper

So changed to ETS Race fuel at $8.30/liter which the engines certainly prefer as had to jet up again and alloy fuel tanks, problem solved

 

[piranha-bro2]

Lucky the regs don't require the use of pump fuel, Red!

Some of those fuel additives sound nasty as - full breathing apparatus in the pits??!!

Octane rating is always a consideration when building a hot street engine.