Final Design

Here is the final design for the 3 speed box. I am going to install a diff and so the rear belt will be 3mm with a 44t pulley on the layshaft.

Contender

I have been sent some pics of a car a guy in the USA is making for the speed event. I know him as Gary O. The car will have 4 engines and is shaft drive. Here are some pics










Best of luck Gary and hope you get it all finished AND TESTED before the event

Design Layouts

I laid out the 3 speed gearbox onto a plate to see if there are any problems. Here is the first layout

As you can see its overly complex and has too much rotating mass

The next layout I tried was this one

This got rid of 1 shaft and 2 gears but also the brakes. The brakes are not as important as top speed so I'll go with this design for the 1st prototype.

This layout has the advantage of being able to easily add extra engines. Just install with a layshaft and feed it though to the gearbox 1st shaft with a pulley

Serpent Clutch Design

To use a Seprpent style clutch for the 2nd speed the assembly needs to be fitted to a one way bearing to allow it to release after the 3rd gear has kicked in. The drawing above shows how I intend to fit a one way from an R12 to the clutch

Design Concepts

The date is set for the 1st Speed event practise for March 16th 2008 at the Shakespeare County Raceway, Long Marston Airfield. I have started on the design concepts for the car that I will be using for the event.

The plan is to have a number of transmission design concepts with only a few fixed objectives. These are to use IC engines to go as fast as possible. Apart from that anything goes.

The design concepts will use the lessons learned from the design and running of the 3 engines Alien car of 2007. It was apparent that the 3 gearbox design didn't work and a single gearbox is required.

The design concepts are

1, 2, 3, or 4 engines
single or separate clutches.
2, 3 or 4 speed gearbox
Belt or shaft drive.

The plan is to test each concept, optimise the design and then list the pros and cons of each to see what parts when used together will result in the highest top speed.

The first design to be tested is the 3 speed gearbox. I have designed the 3 speed box to be able to accelerated the car quickly and keep the car on the power band.

The car needs to engage the clutch at 12,000 rpm no more than 30 mph. This will stop the huge clutch slip I had with the Alien car on starting.

Next the 1st gear will top out at 32,000 rpm around 60 mph.
2nd gear will engage and the revs cannot drop below 22,000 rpm 24,000 optimum

2nd will top out at 32,000 rpm at around 90 mph.

3rd will engage and the revs should not drop below 22,000 with 24,000 optimum. 3rd will then top out at 35,000 rpm at 120 mph

The trial will be with a single .21 engine to see what speed can be attained. and see if there are any flaws in the gearbox design. I don't think 1 engine will pull this gearing so another engine will be added until I can increase the gearing and the top speed.

I have built a 3 speed gearbox using parts from a Schumacher R12. It has the following gearing

Pinion 36
Spur to layshaft 48

1st gear 16/60
2nd gear 24/52
3rd gear 40/44

Pulley to back axle 1/1

I have the gearbox installed on a test bed and have attached an electric motor and a rev counter to be able to set the clutch pawls to engage at the correct speeds. This is 6000 rpm and 10,000 rpm. Here is a vid of the test