Future directions for car development

[trevortennant]

Hi Guys great to see the great Kev resurface. Welcome back to the madness.
What we need is some fresh thinking. Front and rear suspension for a start any idea tell me thanks trevor

[Rocket R/C]

Well I will get this going even though Trev and I talk alot already.

As far as rear suspension goes, the rear swing arm we have now is the most durable, and if the front mounts are lined up with the engine crackshaft properly, it provides the constant arc needed to keep belt tension as even as possible through the suspension range. I think alot of systems could be developed with 4 links in either a birdcage or jacobs ladder configuration, but none would be as strong. It is something worth pursuing. I do know that further development needs to go into rear suspension dampening to start. Putting grease between the chassis rail and swing arm dosent cut it for my taste, we need a shock absorber of some type.

I will leave front suspension where it is for a while, we all know it needs help and redesigning, but lets talk about the rear first.

[trevortennant]

I think that the aspect of constant belt tension is overated. Take a look at a motogp cycle. you would take it as granted that the rear driver sprocket would be inline with the swing arm pivot but they are not. Reason the rear wheels is jacked up and down as the throttle is opened and closed.
God knows how many years ago steve wearing raced a car with vertical action rear axle. the bushes were sprung using coil springs why was it abandoned I will ask him.
Friction damping is simple quite crash proof but the grease gets rubbed off even during a 4 minute race. Is the dry method more consistant? I think so.

[ttracing]

hi trevor can you remember some years ago, if I am correct, I think Kingsway Kars developed a toothed drive system doing away with the drivebelt. Have you any idea how successful it was and what the potential was for future use against the drivebelt system?

[trevortennant]

After that rat stole my revised teethform clutch drum I have had little or nothing to do with him.
i know he looked at a kevlar based belt but nothing came of it. I intend to pursue better fine pitch solutions.
I all fairness the cars in spite of there stone age tech work really well.

[Rocket R/C]

Ah I knew Trev would voice his opinion sooner or later!

I dont think a gear drive is the way to go. I think the direction that Trev and I are pursuing, is a finer tooth belt to give more gearing options, rather than messing with fragile gearing. I think we need to work harder on the suspension design than we do the drivetrain. The rules are pretty restrictive despite the gray area they give you.

I also think the first car that shows up with a gearing setup that isnt direct drive will get tossed out of the meeting quicker than it showed up! Trev is right, these cars do very well for what they are. There is alot to mess with and improve to make them handle better, thats what we should be focused on.

I think the first direction with the rear end could be a birdcage design with the lower link coming forward and the top link going toward the rear attaching near the bumper. A coilover shock could be attached to the birdcage and then to a shock mount up near the window. Coilover shocks should not be avoided on these cars, they would offer a performance second to none, however need to be well protected in case of a hit...... which we all have had many of!

All your thoughts and comments are welcome.... I am researching coil over springs that are strong enough to handle the weight of these, and give good performance, but would still like to discuss it further.

[ttracing]

this is getting all very interesting hi tech or not there good points to be had . personally i would like more life out of the drive belt ?.as it always dumps out on me right at the wrong moment when im trying to qualify for the final

[Rocket R/C]

Well Tom.... belts never liked you because your joggy bottoms didnt have loops

Actually I am finding that belt wear cannot be helped, even with the right setup. This is because we run a 6 tooth clutch drum which is a heck of alot smaller than the belt was ever designed to run on. Also if your belt either loosens or tightens through the range of motion up and down, this can cause it to wear faster also.

Ive found that you want the crankshaft as close to level with the front swing arm pivots as you can. Ideally if you could draw a line straight through the front swingarm pivots and have the crank line up with it, and have the belt at the proper tension, thats your ideal setup....... although its hard to achieve because a 92 is sometimes too short, a 94 is too long, the motor mounts are too short or too tall (short is easy to fix with washers)

All you can do is try and get it as close as you can. I adjust my belt tension with my suspension slightly compressed, that way its perfect in the middle of the range and it wont change too much in either direction. Give that a try.

Also wearing pants with belt loops will help

[trevortennant]

A major improvement to to deburr the sharp edges of the clutch drum teeth. I use a fine grade diamond impregnated rotary burr. To soften the leading and trailing edges then spin the drum in the lathe chuck to polish the outsde diameter of the pulley. The polastic gear should have its edges chamfered. The engine crankshaft sholuld be exactly parallel to the rear axle, Any degree of anglewinder effect will trash belts very quickly

[Rocket R/C]

Good point Trev, all of that makes them last quite a while. You did mine before the worlds and I would have run that one belt for my whole trip over, all the practice rounds and races, but I changed it before the last 2 rounds just as a precaution. Its still a good spare to put on in a pinch, I wouldnt throw it out. Thats the kind of life we should see from these if set up properly. I think I had 15 tanks of fuel through that one belt.

Since we are going down the road of car development, and you brought up alignment of the engine crankshaft and rear axle, lets talk about rear steer. I am using between 1/2 to 1 degree on the electric oval cars with lots of success. It dosent take much to free the car up going into the corner. Its very stable, and the only setback is getting it going straight down the straightaway, the rear axle wants to keep driving it into the outside wall. I dial the trim accordingly and it keeps it together. I think there is alot of merit to this, any thoughts from anyone? I know Trev will pipe up he has played with this before.

[trevortennant]

Rear steer is something I always used. On our return We had a stability issue with front vibrating on entry to corners. I ditched rear steer and things improved. However that was not the problem it was the sliding pin front end even with carefull damping ideas was too sensitive on point and squirt tracks. Worked great on wide open tracks where you do not slow down too much. Have reverted to sliding steering block. The action is dreadful it shudders up and down but hey it works.
I intend to try rear steer again cheers trev ;D ;D

[Rocket R/C]

Rear steer is interesting to play with, but not easy to adjust on stock cars. The only way to make it easy would be to make the right rear swing arm adjustable, or a slightly different length arm to make it longer, then have the rear engine mount post adjustable somehow so the belt would not walk off. Its definitely something that could be done, but we are always mixing adjustability with strength, and seem to give up one or the other. That dosent make playing with things all that easy. Im convinced something could be developed.

On electric pan cars when rear steer is used, again the only setback is that coming out of the corner the car wants to continue to steer toward the inside boards and make a complete circle. A good driver can compensate easily for this, but after the trim is adjusted accordingly, small adjustments can be made to compensate. The bonus of it is the turn in ability is magnificent through corner entry and through the center.... a definite change to drive and requires some practice, but fast!

As much as I enjoy the sliding pin front end, its terribly difficult to dampen easily, thus making bumpy tracks a struggle. Im not big on the sliding block either, but you are correct Trev it works and can be dampened much easier with grease or wax. Still a bit more crude than I would like to see, but until something better is developed.... hint hint..... then I suppose we should switch over..... darn it all!