Experience for Slide on 15/36 for Second Gear?

[mboian90]

Greetings all,

After a long 5 month wait I finally a new fixed 13/38 for my Staffs gear box! Prior to now I have been using a fixed 15/36 that was putting first gear in the 61 MPH range. With my new 13/38 I will also need to acquire a slide on gear set for second which I was planning on being a 15/36 (old 1st becomes new 2nd). After seeing a picture, the hoop thickness of a 15 tooth pinion got me a little concerned. I am curious now on how many people out there are using/have used a ratio in this range in the second gear slot and how well they hold up for autocross.

Based on my previous experience, I would assume I will spend a lot of time in the "new" second gear so it will get used a lot in relative autocross terms. However, a good autocross season for me is probably only 1-2 hours of total race time and a COVID/hurricane season is more like 12 minutes.... Since I have the fixed 15/36 already I would never need to use the slide on gear for first if for some reason I wanted the 61 MPH first gear again.

Matt Boian
CM 14

[CM/FFdriver]

Hey Matt,

Happy New Year, great to hear you got a 13.38 fixed first but you say your in CM but what kind of car?

Now for your question the 15.36 is a great second gear but are your sites very small that 61 mph is good enough, if your plan is to go to the National's sometime soon you may plan on a 3rd gear ratio to get up to 72 to 75mph.

A pic. of your car would be great.

Ben

PS I maybe moving to Texas so see you soon?

[mboian90]

Hi Ben,

This is for the Piper DF2 I had at nationals in 2018. My plan basically adds a new lower first gear and my previous ratios that I have run since 2016 all move up 1 slot (old first is new second, old second is new third ect). The old second/new third is ~73 MPH for me. Since I have a lot of experience with these ratios my only major concern is the life of the slide on 15/36. It is hard to believe 100 HP goes through that tiny thing.

My only other minor concern was having to use the diagonal 2->3 shift more often since I legitimately have only done that for 1 course with my current gearing. At the Texas Tour event I got to drive my friends DB1 which was geared to use 3 gears so I got some practice. It was pretty much a non-issue other than his ignition switch being located next to the shifter when in 3rd gear. Ask me how I found that one out...

Matt Boian
CM 14

[alangbaker]

My only other minor concern was having to use the diagonal 2->3 shift more often since I legitimately have only done that for 1 course with my current gearing. At the Texas Tour event I got to drive my friends DB1 which was geared to use 3 gears so I got some practice. It was pretty much a non-issue other than his ignition switch being located next to the shifter when in 3rd gear. Ask me how I found that one out...

Ask me how I found out my electric fire bottle switch was too close to my shifter...

[CM/FFdriver]

My only other minor concern was having to use the diagonal 2->3 shift more often since I legitimately have only done that for 1 course with my current gearing. At the Texas Tour event I got to drive my friends DB1 which was geared to use 3 gears so I got some practice.
Matt Boian
CM 14

Hey Matt,

I tried the 3 - 4 shifting thing and if you were to have your 4th gear max out at 75 - 80 mph you may bog the engine down a little compared to a 2 - 3 shift with 3rd going to 72 - 75 this should be more then enough for the National thought process with 4th giving you flexibility for an event like Texas.

We have Crow's landing here in Calif. that can get events up 90 mph, Very rare but has happens, my 4th go's until 88mph. I go to events where the events are under 65mph so change my ratio's for those events were 3rd go's to 68mph.

Ben

[Gary Godula]

Matt,

Is that 15/36 a Hewland "M" gear or a brighter, unmarked Webster gear? You want the stronger Hewland gear, if available. I broke several 15/37 Webster gears in the past, the 15 tooth pinion gear would experience a hoop stress failure and break into 3 pieces, which hopefully would just fall to the bottom of the gearbox and not wreak any havoc on its way down. I no longer use a 15/37 as Hewland does not make that ratio.

All of my autocross gears, and almost all of my club racing gears, are Hewland M series, the strongest that they made for the Hewland/Staffs gearboxes. Spend the money up front, and you will not have to worry about it in the future.

[mboian90]

Gary,

I havent acquired the gear yet but was planning on purchasing a new one. I was hoping to purchase through Pegasus since they show one in stock, it is however a Webster "S class" gear and not a Hewland M. I was under the impression both were 9310 so I was assuming they would have similar strength (possibly a poor assumption). Were your Webster failures the newer "S class" or the older 8620 gears? I cant find where I have the decoder ring anymore but it looks like all my Webster gears I noted as 8620 have a "W" in the part number.

Im not against looking elsewhere for a Hewland M of the same or similar ratio however acquiring the integral first was a bit of an ordeal so I would really like to do the easy button and have it be over. To avoid having the integral first ordeal again I would also like to not have second gear explode

Matt

[Gary Godula]

Matt,

I believe I was using the older Webster gears as the time as I do not recall if the S gears were available. The 15 tooth is on of the smallest gears and therefore is subject to the highest hoop stress loads since there is not a lot of material between the root of the tooth and the gear ID.

My current autocross gears are 12/38 fixed 1st gear with a 14/36 Hewland M gear, which, even though the pinion has a smaller root diameter than the 15T gear, has been used for a number of seasons with no issues. I keep the gear ratios close on my car which give me the option to shift a lot or not, depending upon the course.

You might want to contact Taylor Racing in Texas as they used to have a larger inventory of gears than Pegasus and was the go-to shop for all things Hewland.

[CM/FFdriver]

My current autocross gears are 12/38 fixed 1st gear with a 14/36 Hewland M gear, which, even though the pinion has a smaller root diameter than the 15T gear, has been used for a number of seasons with no issues. I keep the gear ratios close on my car which give me the option to shift a lot or not, depending upon the course.

You might want to contact Taylor Racing in Texas as they used to have a larger inventory of gears than Pegasus and was the go-to shop for all things Hewland.

Matt,

Keep up with Gary and his input on things, I've tried a thing or 2 and they have worked.

Gary: Wow I'm using the same ratios in my car for the last year, very interesting because It's hard to come up with definitive data because we have different courses every event, one event I kick ass in the Pax the next event I even doubt the data because I'm slower then before with only making up a .100 or .200 each lap, frustrating.

Matt: It's best to try different gear ratio's all the time with good data, for one to become more efficient at changing gears but to get a good feel at changing gears. One thing is don't do 2 gears my feeling is it doesn't work, you get too low in the RPM range and then to high, you want the car to pull through all the gears.

Ben

[Gary Godula]

Matt,

Does your transmission have a 9/31 or a 10/31 final drive? We have a 10/31 in the Reynard, which is why I opted for the lowest fixed 1st gear available....12/38. I also ran a lot of Pro Solos at the time and needed the launch capability. I am usually shifting between 2nd and 3rd a lot in my car, but I never really found that to be an issue. Gearing was usually 45mph 1st, 56 for 2nd, 65 for 3rd, and 82 for 4th. Maybe the course speeds have changed since I was racing a lot, but this gearing gave me a lot of options, though it did require a lot of shifting.

Ben,

I have no idea why you or anyone else would ever really listen to me, but I appreciate the kind words. I do not know what the current gearing trends are within the class, particularly with the Brand H powerplants, but I am willing to share what worked for me over the years....a long time ago.

[CM/FFdriver]

Ben,

I have no idea why you or anyone else would ever really listen to me, but I appreciate the kind words. I do not know what the current gearing trends are within the class, particularly with the Brand H powerplants, but I am willing to share what worked for me over the years....a long time ago.

Gary,

When people talk, I'll listen.

Ben

[mboian90]

Does your transmission have a 9/31 or a 10/31 final drive?

Gary,

I have a 10/31 with a "Brand H" powerplant. Ive been racing the past 5 years with a ~60 MPH first gear, launching is about as exciting as you would expect. Other than that I dont have major complaints with what I have been using which is why I was opting to add a lower first and leave the rest the same. There is probably more "optimizing" that can be done but I would easily negate that with my driving. I will worry about it later if I can ever keep up with you and Ben.

Matt Boian
CM14

[Gary Godula]

[QUOTE=mboian90;618425]

I will worry about it later if I can ever keep up with you and Ben.

Considering that I have run 2 Pros and attended Nationals once in the last 13 years, and performed horribly at each, everyone is faster than me. You are already doing much better than me.