SR Help

[B_Regal Racing]

Looking to jump into the SR class. I have a body built/painted, windows installed, bumpers, lights, etc.; but I'm intersted in how others attach it to the car. Would anyone want to share a picture of the underside? Just trying to get ideas...

Also interested in the chassis itself. I have heard that if you have built an SS, you have built the chassis for an SR. That being said, has anyone used a ladder frame as an SR chassis. I typically use this style as my SS / BASX bodies, coming in at about .3 to .4 oz. Is this too light for an SR chassis?

 

[quadad]

Great to have you join the SR class B_Regal !! There is something really cool about watching these cars go down the track and if you like that, you migiht as well 'have a dog in the hunt' !

There are a few picture sets in the forum already, starting with Joel's day one attempt by using horizontal screws into the sides of the chassis. Some have put balsa blocks and vertical screws and a few have taken it to another level lately (I am not one of those, yet). Bottom line is finding a way to get it to work on the track with minimum weight penalty while easily attaching/detaching and surviving shipping. I am not recommending my method (small wooden blocks and plastic nuts cemented under the body to support screws through the bottom of the chassis) as it takes too much careful alignment work, and time, during the build.

I am not sure I would agree with the SS chassis comparison. In general, I think that SR chassis are simpler, though they have to support the attachment approach. You only have to worry about aero effects on the bottom of the SR chassis. Most people are covering up the open spaces under the body with one material or another. Because the chassis profile is not what is seen on the track, there is more freedom with how you weigh the car in a SR chassis. COMs are a bit further forward both in dealing with the car structure as well as the often narrower wheelbases.

We are learning more about what makes a good body for an SR car and that can possibly depart from your favorite car body. I have been taking a hard look at that lately. In general what I think is most important is where the weight COM will end up (a function of the where the rear axle will be and the wheelbase) and the frontal area of the car. As these cars are MUCH more affected by neighbor vehicles, width seems to be especially important. Lots of tradeoffs all around though since cars that are extreme in any one dimension seem to present unique challenges. If at all possible you want to run these cars on a track before sending them in. I have had rear wheels scrape the underbody when going through the transition when I expected adequate clearance.

Hopefully more will add to this and more will join the class !!

 

[Crash Enburn]

There are two camps here: One camp finds a cool car, builds it, and submits it to races. The other camp looks for a car solely based on aero and/or mechanical advantage ("a good body for an SR car and that can possibly depart from your favorite car body").

I am of the "show" camp. And I'm very happy to hear that your car has a grill, bumpers, lights, etc.

As to the chassis, I've used the method that QT showed a while back (http://www.pinewoodderbyonline.com/post/show_single_post?pid=1276284512&postcount=19). Unfortunately his pics are no longer there. In essence, you build a chassis. In the body of the car, you mount two mounting strips of wood. In both of those strips, you drill two pockets that will accept your screw heads. In the chassis, you screw in two screws to the sides that will then slot into the pockets in the mounting strips. You can adjust how much pressure the screws exert on the body (to hold it on firmly without overstressing it) by turning the screws in or out.

The (stillborn?!) Diablo VT Roadster I was/am building will require different mounting. I'm looking at a mounting block in the front of the body that the chassis will either slot or screw into, and then screws into a mounting block in the back.

 

[Guest]

There are two camps here: One camp finds a cool car, builds it, and submits it to races. The other camp looks for a car solely based on aero and/or mechanical advantage ("a good body for an SR car and that can possibly depart from your favorite car body").

I am of the "show" camp. And I'm very happy to hear that your car has a grill, bumpers, lights, etc.

As to the chassis, I've used the method that QT showed a while back (http://www.pinewoodderbyonline.com/post/show_single_post?pid=1276284512&postcount=19). Unfortunately his pics are no longer there. In essence, you build a chassis. In the body of the car, you mount two mounting strips of wood. In both of those strips, you drill two pockets that will accept your screw heads. In the chassis, you screw in two screws to the sides that will then slot into the pockets in the mounting strips. You can adjust how much pressure the screws exert on the body (to hold it on firmly without overstressing it) by turning the screws in or out.

The (stillborn?!) Diablo VT Roadster I was/am building will require different mounting. I'm looking at a mounting block in the front of the body that the chassis will either slot or screw into, and then screws into a mounting block in the back.

If you search long and hard, you can find a good looking body that is aero as well and have the best of both worlds. They are out there.

 

[B_Regal Racing]

As to the chassis, I've used the method that QT showed a while back (http://www.pinewoodderbyonline.com/post/show_single_post?pid=1276284512&postcount=19). Unfortunately his pics are no longer there. In essence, you build a chassis. In the body of the car, you mount two mounting strips of wood. In both of those strips, you drill two pockets that will accept your screw heads. In the chassis, you screw in two screws to the sides that will then slot into the pockets in the mounting strips. You can adjust how much pressure the screws exert on the body (to hold it on firmly without overstressing it) by turning the screws in or out.

Those were what I was look for; I could not remember who though. The description should be enough for me to work with.

I am not sure I would agree with the SS chassis comparison. In general, I think that SR chassis are simpler, though they have to support the attachment approach. You only have to worry about aero effects on the bottom of the SR chassis. Most people are covering up the open spaces under the body with one material or another. Because the chassis profile is not what is seen on the track, there is more freedom with how you weigh the car in a SR chassis. COMs are a bit further forward both in dealing with the car structure as well as the often narrower wheelbases.

Also what I need. Between these two posts, I think I have an idea.

Strangely enough, CnB, you'll be particularly interested in my SR. I'm hoping to get it together for this upcoming race, but now reading, the chassis I have may not work. I guess, however, I can remake the chassis simply enough. I'm assuming you all do that (build another chassis as necessary) and just reuse the body for some period of time.

Thanks for the help.

BTW: I did go "old school muscle car"; it's probably not the most areo shell of a body out there.