The Mitchell is IN!

Probably not all that hard.

Start at the 12 o'clock position.

3.78 would be 3 plus a bit after 9 o'clock .

3.70 would be 3 plus a bit before 9 o'clock.
 
2nd gear OD with the Mitchell is a wonderfully useful gear, and still quite a bit lower than 3rd, due to the large gap between 2nd & 3rd. Not sure, but I think 35 mph or so is easily obtained. It is super useful in many mountainous areas, where 3rd is too tall, and normal 2nd is too low. I also find it useful in heavy traffic, where 3rd is too fast. I also think the standard 3.78 ratio works perfectly with the Mitchell, which gives 26% OD. In 3rd OD, I can even pull modest hills with my HC head. Most of the BW units are more like 33%, which to me, is too high.
 
Hoogah, NO you cannot simply remove the center bolt, because the spring is still under pressure even when free from being shackled. I recently replaced a center bolt with the spring removed from the rear axle and shackles and carefully installed 4 large heavy duty "C" clamps and also wrapped a heavy duty chain and bolt/nut, before removing and replacing the center bolt.
 
Thanks, Pat. I couldn't figure out where the pressure would be coming from if the ends of the spring are free, but groing by your comment, there must be pressure exerted by the lower leaves progressively towards the top leaves - i.e. the consistent curve that you see when the spring is bolted together is only there because the bolt is pulling each spring's own curve into line?

I'm certainly going to keep this in mind if I ever need to work on it again. I think I was lucky!
 
Actually, I replaced the spring with a new spring that came assembled and I took it apart to add graphite (slip plate) to each leave before reassembly. I was amazed at how much spring compression was required to press the spring assembly back together to reinstall the bolt. I used a 12 inch long threaded rod and nuts to slowly reassemble/compress the spring assembly with large C clamps, gradually cranking everything down so that I could reinstall the bolt. This is a dangerous job, working with a spring and you must be very careful.
 
I neglected to mention that when my new spring arrived in the mail, I knew that I would need to disassemble it, grind/bevel the edges of the underside of each leaf, and lube with slip plate. For disassembly, in used 4 large C clamps and a chain wrapped around the spring prior to removing the center bolt. Upon removing the center bolt, after the spring was secured by the C clamps and chain, I quickly slid in a 12" threaded rod with flat washers and nuts and tightened them down again the spring, and then I slowly released the C clamps and in turn slowly loosened the nuts on the 12" inch threaded rod, until there was no more compression. At this point the distance between the 2 nuts on the threaded rod was at least 8 inches, so I could clearly see that the 4 inch center bolt was holding the spring in compression. After lubing and ginding/beveling of each leaf's underside, I reversed the disassembly process. I hope this procedure makes sense to you; it's what I did, but others may have a better process. I just want to reinforce that the rear spring/leafs are under pressure even after they've been carefully released with a high quality spring spreader from the shackles and rear axle.
 
Great description, Pat. I get it now!!! That's a lot of compression held together by the centre bolt (as Tom Endy warned me originally!!) :(
 
Hoogah - Here is a photo to help you visualize what I did.
 

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Pat Marone has it right. CAUTION anytime you are around a spring assembly. The technique pat used is exactly how I do it. A belt sander is the best way to cleanup each leaf. You will generate alot of rust dust so pick a spot where you can work. The slip plate is a domestic product (USA) The big model a parts houses carry it. It is a grafite based brush on, or in an aerosol. grafite and varnish should work for a home brew alternative. You will have a serious mess on your hands, not to mention a dangerous situation handling the spring to reassemble and install if you prelube without the slip plate.
 
As I have mentioned numerous times before, the rear spring on a Model A Ford can be lethal. However it only becomes lethal when it is spread to the distance to attach it to the rear axle assembly.

When the spring is attached to the frame of the car, it is not going to go anywhere. The danger though is not correctly attaching the spring spreader. it should be a proper spreader that captures both shackle bosses. An improperly attached spring spreader or one that is jury rigged can fire that spreader across the room like an ancient cross bow.

Bringing the spring out along with the rear axle assembly is a dangerous practice, yet people do it all the time and advise others to do it as well. The center bolt head can pop off, or a shackle can break. Working over the spring like that is not safe.

The safe procedure is to spread the spring, drop the rear out and leave the spring attached to the frame. You can leave it that way indefinitely until you are ready to re-install the rear. However, if you have small children around it would be prudent to back the spreader off and remove it. The spring then is of no safety concern

When the tension if off the spring it is no longer lethal and it can be safely removed from the car. It still contains a small amount of tension, but it is not lethal or dangerous. By putting a C-clamp next to the center bolt it makes it easy to unscrew the nut and pull the bolt out. Back off on the C-clamp and the leafs will separate and you can see how little tension was left in the spring.

When restoring an old cruddy spring I bead blast all the leafs and grind off all the witness mark indentations and round the lower edges at the bottom of each upper leaf. I spray slip ease between the leafs. I always install a new center bolt and nut. Suppliers sell them much longer than required. This to allow the bolt to be slid though all the loose leafs. However, once you have done that put the C-clamp back on and pull the leafs together. This will make it easy to run the nut down

When the nut is tight cut off the extra length and peen the end to keep the nut in place. Make sure the square head of the bolt is aligned properly to center in the square hole in the frame. Give the spring a shot of black paint and it is ready for installation.

Reinstall the spring in the car. Do not attached it to a removed rear. Once the spring is attached to the frame install the spring spreader and spread it enough to accept the re-installation of the rear.

The above is the safe way to go about it. Give that rear spring all the respect it deserves.

Tom Endy
 
Thanks Tom, no substitute for your experience. I will modify the way I handle the rear spring from this day out. I don't have access to a media blaster large enough for the springs. The media would be kinder to the springs than the belt sander. The pitting I have encountered would be filled with the slip plate. Bob
 
Tom Endy said:
...Bringing the spring out along with the rear axle assembly is a dangerous practice, yet people do it all the time and advise others to do it as well...
Click to expand...
Just last night I was watching one of Diablo's DVDs on re-arching springs. They even demonstrated taking the rear axle assembly out with the spring attached.

I would still prefer to do it Tom's way. Sounds/looks much safer!
 
Was the re arching video done cold in a press ?

I read a while ago here, a guy re arched the main front spring leaf upside down to get a reversed eye in a press cold .
 
Thanks Hooga! I am contemplating installing a Mitchell in my recently completed 1930 Cabriolet. I checked here to read what people are saying about them and I noticed your article. Great narrative! I will probably go forward with mine soon. Hey by the way, we are all getting great advice here on the site and for those that WARNED you about not doing something "ill-advised" (stupid), there is not a man alive that has not done an ill-advised stunt on his Model A. Welcome to the club buddy. You survived to fight another day. Stay safe and enjoy the ride. Scott
 
While at the MAFCA convention in Puyallup, WA I was talking to Steve Mitchell. He says there is a chapter that about half of the members are running Mitchells in their As. They claim to be able to do the install in two hours. Now that must be an interesting sight when they make that installation!
 
JohnLaVoy said:
While at the MAFCA convention in Puyallup, WA I was talking to Steve Mitchell. He says there is a chapter that about half of the members are running Mitchells in their As. They claim to be able to do the install in two hours. Now that must be an interesting sight when they make that installation!
Click to expand...

TWO HOURS!!?? Makes my 18 hours for two first-timers look kinda lame! I wonder how many people they have working on each car?

John, did you happen to get a card from Steve with an email address on it? Seems like he doesn't have one? If you have an email contact, I'd love to get in touch and provide some feedback. (Suppose I could write a letter, but I've forgotten how . . .:rolleyes:)
 
If you don't have the experience and don't prefit the stubb shaft to the pinion assy and mess up the shaft and then have a rough time pressing off the pinion carrier then 18 hours for a first time, remote location install I would say is very respectable. We had the luxury of quick service from Mitchell. They had a replacement stubb shaft on hand for guys like us, and they are close enough to drive to if we managed any serious misinstallations. Spring problems would add to the elapse time. It definately gets quicker each time you do one.
 
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Hoogah said:
TWO HOURS!!?? Makes my 18 hours for two first-timers look kinda lame! I wonder how many people they have working on each car?

John, did you happen to get a card from Steve with an email address on it? Seems like he doesn't have one? If you have an email contact, I'd love to get in touch and provide some feedback. (Suppose I could write a letter, but I've forgotten how . . .:rolleyes:)
Click to expand...

Hey Hoogah,
Thanks much for such detailed (with pics for us image challenged:)!) article...congrats ! I was struck by two items that you mentioned, that is...that you have some good ideas that may should be considered by Mitchell for improvement in their info for installation by first time installers and I know that you said that you couldn't locate past threads for installation, BUT, I know that there must be a ton of thread talk on the dangers of working with springs on Model As ! I'm wondering how/why you missed spring danger threads , as plenty here also work on such springs and maybe benefit from your input. And, maybe you can give Mitchell your valuable input on how to improve written presentation , with pics, as you said.
BTW... you are one lucky guy to have such experienced Model T mechanic friend ! I'd bet that he could add to the recommendations for improvement of written install instructions.
 
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