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Old 09-12-2021, 11:38 PM   #1
Outback
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Default Model T Ring gear,

G'day,

I'm new here to the Ford Barn, but have been over on the HAMB for some time,

I have a question for you guys. I am looking for the dimensions for the Model T Ring Gear & Pinion, not the ratio so much but the diameter primarily, but also the width.

The reason for this is because at work we play with all manner of European vehicles & are looking for an off the shelf diff center for a very small french cyclecar.

The other question is how much horsepower can the model T diff reliably cope with?? I hope my question's make sense, somtime's my Aussie accent/language is lost in translation.

Regards
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Old 09-13-2021, 08:23 AM   #2
rotorwrench
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Default Re: Model T Ring gear,

I can't tell you dimensions but I can say that is is likely too wide for a three wheel cycle such as the Harley Davidson servicar or even the Pashley Enfield Indian single cylinder bullet type three wheeler conversion that was sold in the US under the Indian patrol car name back in the 1950s.

The model T uses tapered axle shafts and straight cut ring & pinion gears. The model T was a 20-horse power set up and many didn't have wheel brakes like the later cars. The rear drum brake set up was for the emergency or parking brake. Actual braking was done in the rear of the transmission. The transmission was a 2-speed planetary unit very unlike any modern systems. The wheels and hubs were integral on early models.
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Old 09-13-2021, 10:39 AM   #3
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Default Re: Model T Ring gear,

There are a good number of guys working on T's in Australia. Your quest might work better if you could physically have one in hand to look at. You could post over on The Model T Ford Club of America in the general forum. If you do post there, put that you are located in Australia in the title. By the way, you can use your common Aussie terms for the parts, many know what they are.

As rotorwrench said, the teeth are straight cut and may or may not work for your application if the sizes are workable.
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Old 09-14-2021, 07:16 AM   #4
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Default Re: Model T Ring gear,

Thanks guys, we won't be using the whole diff, just the crown wheel/ring gear & pinion. We will use the Amilcar diff housing & axles & machine parts to fit, if it - ring gear - will fit.
The alternative is to have a new gear set manufactured. But that = $$$'s
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Old 09-14-2021, 09:51 AM   #5
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Default Re: Model T Ring gear,

There must be quite a few choices to three wheeler rear differentials out there with all the factory built and conversion set ups now available. They would already be set up for chain or belt drive as well.

The model T has a straight tooth ring could be made to fit some other carrier but the pinion is set up to work on a tapered shaft with a key way. I assume you are looking for gears to make a shaft drive set up. If so, will it be rigid or will it be made to move with a suspension of sorts? You may want to consider Model A type gears. At least they are helical cut types that would be a lot more quiet when operational. They also use a tapered shaft type pinion that is non-hypoid. The ring bolt circle is likely close to 8-inches on both types but I can't find any figures on diameter. The model T gears likely have a some whine to them when they get up to higher speeds. They weren't designed to go much more than 50 mph.
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Old 09-14-2021, 05:49 PM   #6
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Default Re: Model T Ring gear,

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Thanks Rotorwrench,

In this case the Amilcar has a conventional diff with universals & tail shaft. We looked at an A model center as I had one loose but it is too large in Diameter.
I didn't know T's were straight cut.
This mix n matching is what gets done here at work. One of the boys is putting a v8 gear set in an early 20's Vauxhall diff.

I'm just trying to find the sizes so we can work out if it will go in, as I don't know anyone with a T diff in bits.

Last edited by Outback; 09-14-2021 at 10:25 PM.
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Old 09-15-2021, 04:21 AM   #7
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Default Re: Model T Ring gear,

Hi Outback


Can you let us know a contact details. Wouldn't mind having a chat about what you do.
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Old 09-15-2021, 10:26 AM   #8
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Default Re: Model T Ring gear,

America Bantam and Crosley cars had small rear axles but they may be too small and have too low a ratio . It would be interesting to know what diameter and ratio may be optimal.

The gears are made from a chunk of steel but the cutting hobb or hobbs needed to machine them can be quite expensive to have made. Not every machine shop has a gear hobbing machine.
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Old 09-15-2021, 01:17 PM   #9
Dan McEachern
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Default Re: Model T Ring gear,

A 40 tooth T ring gear (crown wheel) has an od of 8.100" and the id mounting diameter is 5.248". The threaded mounting holes are on a 5 13/16" bolt circle.


Hope this helps.
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Old 09-15-2021, 07:50 PM   #10
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Default Re: Model T Ring gear,

Dan thankyou so much, that is what we were looking for.
Is a 40 tooth ring gear 3.5 (ish ratio?)

29 Vintage, I can't PM as I don't have enough posts yet. Where are you?

Rotorwrench mid 3's would be optimal, the car will be running a 90CI HAL
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Old 09-16-2021, 05:57 AM   #11
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Default Re: Model T Ring gear,

I had a chance to measure the crown wheel we will be replacing it is 7 1/4" Thankyou for your time folks
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Old 09-16-2021, 10:49 AM   #12
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Default Re: Model T Ring gear,

Ring and pinion gears are generally always made as a matched set. To find a ring that will match some other pinion design is a lot worse than looking for a needle in a haystack.

Some of the new CNC gear machining centers don't use a hobb to cut a helical spiral bevel type gear. They use a radius cutter with replaceable blades that can be adjusted to the radius of the spiral bevel and the tooth cutters will be the proper width for the pattern gear cut. They are expensive machines so I don't know what it would cost to do set up and cutting but it would likely be prohibitive for a one off set of gears.

I hope you find what your looking for. Amilcars were rare even well before I was born. Isadora Duncan lost her life in one of the open wheel sport models. She should have been more careful with her use of scarfs. C'est la vie.
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Old 09-16-2021, 01:49 PM   #13
Dan McEachern
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Default Re: Model T Ring gear,

That crown wheel will run with either a 10 tooth or 11 tooth pinion, so the ratio is 4:1 or 3.63.


Have you checked a Nash Metro rear end for size- recall those were BMC or something similar. any way- pretty small and might work.
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Old 09-16-2021, 03:06 PM   #14
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Default Re: Model T Ring gear,

Ts with straight cut teeth don't seem to have the same issue when it comes to mesh as the As do. People mix and match them all the time. Ok that is not 100% re the Ts, but in most cases they run just fine.
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Old 09-16-2021, 06:42 PM   #15
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Default Re: Model T Ring gear,

Outback, I'm located in SE Qld, Aust.
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Old 09-16-2021, 10:25 PM   #16
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Default Re: Model T Ring gear,

We certainly would using a matched set of gears, the reason for primarily asking about the ring gear is that is the major problem in terms of diameter. It would be nice to be able to buy an off the shelf set of gears, rather than forking out big dollars for a one off set.
The Amilcar is something like 5:1 & we are looking for mid 3's
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Old 09-16-2021, 10:26 PM   #17
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Default Re: Model T Ring gear,

29Vintage, that's my stomping ground.
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Old 09-16-2021, 10:31 PM   #18
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Default Re: Model T Ring gear,

Quote:
Originally Posted by Dan McEachern View Post
That crown wheel will run with either a 10 tooth or 11 tooth pinion, so the ratio is 4:1 or 3.63.


Have you checked a Nash Metro rear end for size- recall those were BMC or something similar. any way- pretty small and might work.
Dan, Nash's are very uncommon over here & most pommy cars have a very low ratio, will keep looking, thanks.

I also didn't know that the pinion count changed but ring gear stayed the same, facinating!
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Old 09-17-2021, 10:02 AM   #19
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Default Re: Model T Ring gear,

Of the Nash Metro ring & pinion sets on flea-pay, the tallest one is 4.22:1 but they are pretty small. Kits to change to 3.90:1 are available.

The MG Midget or Austin Healey Sprite with the 3.90:1 might be better. I've seen that the 3.55:1 ratio may be available now. BMC built the components for Nash Kelvinator so the stuff may be similar.

A lot of these cars were sold in the US so there is a lot of stuff available for them here.

Last edited by rotorwrench; 09-17-2021 at 10:24 AM.
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Old 09-18-2021, 03:17 AM   #20
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Default Re: Model T Ring gear,

Ok thanks. Austin 7 is another thought i have had in the last couple of days. Pinion needs to be on axle line like early fords. Can't remember the term ��
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