Technical Forums => Restorations => Daves Garage => Topic started by: MiniDave on June 22, 2021, 01:19:18 PM

Title: Sprite Race Gearbox Build
Post by: MiniDave on June 22, 2021, 01:19:18 PM
I now have 3 of these to do for various people, so I'm going to incorporate all of them into one thread, and try and document every step of the build. All will have tall, close ratio straight cut gears and regular synchros.

I'll be starting these sometime next week, so stay tuned!

In the pic, the black one is done and ready to be picked up this Friday, and another one is on the way to me from out of town.

(Yes, I need to sweep the leaves out of the shop!)
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on June 24, 2021, 12:42:06 PM
Black gearbox picked up today, I hope he never has to use it because he has a dogbox in the car now, but if he does it's ready to go.

I got a call this morning from another racer who is also sending me a gearbox to do, I think I need to raise my prices!

Edit: Third gearbox showed up today, so I need to get some parts on the way for it. I'm planning to do these one right after the other.....
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 21, 2021, 02:32:29 PM
Wow, 2 more Sprite gearboxes have shown up today for straight cut gear sets......I'm getting to where I can do these in my sleep!   8.gif

I think I need to raise my prices!  ::)
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 24, 2021, 09:20:33 AM
Wow, this first gearbox is an absolute was partially disassembled when it came into the shop and when I finished taking it apart I found all sorts of things wrong, detents in the wrong place, balls instead of plungers - the wrong springs used, parts missing.....I hope I have enough left over scraps from other boxes that were junked to build this one. Some of the little parts I need are just not available anymore.....

I can always tell when someone has been working on one of these - or on a Mini engine - things like nuts removed with a hammer and chisel, RTV squirting out of every joint and of course, things put together wrong. I'm surprised this one even worked - if it did!

The bearing plate is supposed to have a round hole with a peg in it to locate the plate in the correct orientation - I'm not sure how I'm going to fix that....I may have another plate but I know I don't have the peg, and those are not available.

One interesting thing I found - the splines on the input shaft (where the clutch disc rides) are the same as the splines on the output shaft where the driveshaft slips into the gearbox - so I use a driveshaft yoke to hold the shaft so I can tighten or remove the big nut on the shaft - instead of using a hammer and chisel like they did on this one.

Just got the email from DHL on my Mini parts, it says Wed delivery - which usually means Tuesday so, the race is on! I think the parts from Virginia will get here first, but the ones from California might get beat by the ones from England!
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 26, 2021, 04:02:46 PM
In the pic above the hole the peg is supposed to fit into is damaged, and I found the missing plug buried in the case. I also found another plate and plug so I won't need this one, but I'll keep it just in case. The old plug is damaged, but i think I can save it by working it over with a file, and I can redrill the hole in the plate that it fits into. It won't be prefect but then it only has to locate that plate....there's no force on it once it's all together.
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 26, 2021, 04:09:03 PM
Some misc bits I've found that were not right or just messed up...

In the first pic the springs on the left are what I found in the gearbox in various places, the ones on the right are what's supposed to be in there. A couple of them look like they came out of a ball point pen or something!

In the second pic - I had a lot of trouble getting the shift rods out of the forks and the case, the middle screw shows why. The tapered end fits thru the shift fork and into a hole in the shift rod. the two outer ones were screwed into the shift rod so hard that they deformed the hole in the rod, so it had to be driven out of the shift fork. The middle one missed the hole but was tightened up anyway, mashing the end of the tip - I'll replace that one. The other two are usable but it's not necessary to screw them in so tight.....there is a star washer under the locknut - you want them tight enough that the fork doesn't move on the shaft, but that's it.

I've got everything cleaned up and ready to go back together now, I'm just waiting on parts to show up - same with the Mini gearbox. Once those get here I can crack on with both jobs - we're trying to get the Sprite gearbox done in time for him to make a race Oct 8,9,10 at Hallet, so as soon as it's done he needs to grab it so he can get it installed in his racecar.
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 26, 2021, 04:25:06 PM
I think the reason they thought they had to use so much RTV on this gearbox is because they used a hammer and chisel to take it apart - I found some more damage to the case where they drove a screwdriver or chisel between two pieces to get a small cover off.

I also found a lot of stripped threads, I've re-tapped all the blind holes and I'll use blue locktite on the studs that go in them to make sure they hold OK.

Title: Re: Sprite Race Gearbox Build
Post by: 94touring on September 26, 2021, 06:10:59 PM
Looks like a lot of work to me!
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 26, 2021, 07:04:01 PM
Yes, it is....... :(

Especially when you just finished putting something together and realized you forgot one little tiny bit and you have to take it apart again. And then you take it apart to put the tiny bit in and it won't go, so you have to take it apart further to figure out why that piece won't go in - then when you do figure it out and fix it, then you have to put it all back together again, only this time it doesn't want to go back together, where it did easily a minute before....   :-[

BTW, Moss Virginia won the race, and I think between what they sent and what I have on hand I have enough to finish the gearbox, so he should have plenty of time to put it back in the car and get it run in.   4.gif
Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 30, 2021, 02:27:43 PM
So.....this one is done - sort of. Everything inside is finished and it shifts beautifully. Clancy brought me a front cover - he has a guy who machines them and puts a lip seal inside so they don't leak oil thru the mainshaft. Originally, they have a sort of reverse thread that's supposed to scroll the oil back into the box, but the front covers wear and the gap gets big enough that they leak thru and it gets on the clutch, this helps eliminate that.


He brought me the wrong one - he brought one for a smooth case gearbox, and the bolt hole pattern is different.

So I have it all done save for that. He was supposed to get it on Tuesday so they could put it in a car for the races at Hallet, if they can work out the pick up schedule OK they still have plenty of time to get it in the car.

All I have to do is measure the cover so I know what size shim to put in it and bolt it on, won't take 15 minutes once I have the right cover. In the meantime I have a small bracket bolted on to hold the input shaft bearing in place.

With this one done I can now get back to work on the Mini gearbox as all the parts are here for it. I'm hoping that the various machine shops will be done with their work on the engine block, head and crank by tomorrow afternoon, but I have plenty to do in the meantime.....

Title: Re: Sprite Race Gearbox Build
Post by: MiniDave on September 30, 2021, 04:24:33 PM
I threw a coat of paint on it - I wouldn't normally paint one white but that's what color it was when it came to me, so......

Just heard from one machine shop - block, pistons and crank are done for the Mini engine, I'll go get them tomorrow.