correct angle or measurement for front axle caster
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Topic author - Posts: 12
- Joined: Wed Jan 09, 2019 9:48 am
- First Name: Frank
- Last Name: Harris
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- Location: Long Beach, CA
correct angle or measurement for front axle caster
We are attempting to build a copy of Terry Horlick's "Toady" who graciously sent us a copy of a set of his own one off plans for the build. As suggested by Terry, we are using a TT frame in order to balance the rear end passenger load better at speed. Because of the fact that the Laurel blocks lower the front end, we have Zee'd the rear of the frame to conform with the desired body stance. We are looking forward to helpful information on this matter.
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Re: correct angle or measurement for front axle caster
Frank: The Ford service bulletin July, 1921 (From Ford Service Bulletin Essentials pg 202) states that the spring perch is built with 5-1/2 degrees of castor, meaning the axis of the king bolts make an angle of 5.5 Degrees to the ground, top hole is rearward of bottom hole for kingbolt. Here is an earlier discussion showing Ford specs for Castor. Using a square from a flat floor up against the king bolt bushing bosses on the front side of the axle, the top boss should be 1/4 to 3/16" to the rear of the bottom boss. IIRC, the Ford measurements recommended when using a square gave less than the 5.5 degrees Ford claimed they built into the perches, but most people adjust with the square method and things seem ok. http://www.mtfca.com/cgi-bin/discus/sho ... post=78296 Best, jb
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Topic author - Posts: 12
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- First Name: Frank
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Re: correct angle or measurement for front axle caster
Thank you Jim and I understand that the faster you go the more caster you need. So I will set up originally at 1/4" remembering that there is about an inch and a half of threads and that I have the jam nut set at half way. I think I will screw it in a little more because the thread count is so close together that I can adjust the length by a very small few thousands of an inch at each turn of the castellated hex nut with a cotter pin.
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Re: correct angle or measurement for front axle caster
Don't forget to check the tow in after any change in caster. Because of the camber, changes in caster will change the tow in.
Here is a good tread on caster math: http://www.mtfca.com/discus/messages/822076/847393.html
Here is a good tread on caster math: http://www.mtfca.com/discus/messages/822076/847393.html
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- First Name: Erik
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- Location: Auburn, Ca.
Re: correct angle or measurement for front axle caster
When I built first speedster I set it up with specified caster. Didn't work on this light car with Corvair steering box. I had to double it and now it tracks fine. For your car I would suggest a little more than stock caster as it will clearly by faster than a stock car.
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Re: correct angle or measurement for front axle caster
Frank,
That's a photo of "Toady". I sure wish I still had that car. After I sold it Terrie told me that was the only car I had that she liked!
You may be interested in the car I have sitting in the garage awaiting restoration. I wanted one which can carry Terrie's friends or lots of kids. I hope she will like it too!
Terry[/color][/size]
That's a photo of "Toady". I sure wish I still had that car. After I sold it Terrie told me that was the only car I had that she liked!
You may be interested in the car I have sitting in the garage awaiting restoration. I wanted one which can carry Terrie's friends or lots of kids. I hope she will like it too!
Terry[/color][/size]
Terry Horlick, Penn Valley, CA
1927 Mountain Patrol Vehicle from the Los Angeles City Fire Department (L.A.F.D.)
1912 Model T Ford English Station Omnibus
1927 Mountain Patrol Vehicle from the Los Angeles City Fire Department (L.A.F.D.)
1912 Model T Ford English Station Omnibus
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- First Name: Ed
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Re: correct angle or measurement for front axle caster
Hey Frank, using the straight edge (big carpenters square) resting on the floor and against the bottom of the yoke casting, the distance between the straight edge and the top of the yoke casting is 5/8-11/16 inch. on old #4 and I could not be more comfortable at 80 MPH. Same at speeds above 80 MPH just a lot more vibration. Hope this helps a little.
Ed aka #4
Ed aka #4
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Re: correct angle or measurement for front axle caster
Ed's suggestion makes sense. It allows for any fall in the floor. Rather than measure at the castings, would it not be more accurate to measure to the top and bottom king pin bush flanges. Can anyone tell me what the difference should be if the caster is set at 5 degrees? It's been a long while since I did any trigonometry.
Allan from down under.
Allan from down under.
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Re: correct angle or measurement for front axle caster
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The past is a great place and I don't want to erase it or to regret it, but I don't want to be its prisoner either.
Mick Jagger
Mick Jagger
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Re: correct angle or measurement for front axle caster
Allan,
First of all my apologies, I grabbed my metric verniers when I went out to my car...
I get 117mm between the centre of the bottom and top flanges. At 5 degrees the difference from vertical would be 10.2mm, at 5.5degrees it's 11.2mm.
Also, when I did my alignment recently I used a cross-laser level for this task. It made it very easy, and accurate.
First of all my apologies, I grabbed my metric verniers when I went out to my car...
I get 117mm between the centre of the bottom and top flanges. At 5 degrees the difference from vertical would be 10.2mm, at 5.5degrees it's 11.2mm.
Also, when I did my alignment recently I used a cross-laser level for this task. It made it very easy, and accurate.
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Re: correct angle or measurement for front axle caster
117mm = 4.606inches 10.2mm = 0.4018 inches 11.2mm = 0.4410 inches
https://www.google.com/search?client=fi ... +to+inches
https://www.google.com/search?client=fi ... +to+inches
The past is a great place and I don't want to erase it or to regret it, but I don't want to be its prisoner either.
Mick Jagger
Mick Jagger
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- Posts: 5259
- Joined: Sun Jan 06, 2019 7:21 pm
- First Name: Allan
- Last Name: Bennett
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- Location: Gawler, Australia
Re: correct angle or measurement for front axle caster
Thanks Luke and Frank. I am looking to make a fixed tool to use to check this. I had thought of screwing fixed metalthreads into a 6" spirit level body, but that would only be usable if the car is parked on a level floor. Ed's use of a large square takes the level floor out of the equation an make my tool more practical to use. With the square in position, all that needs to be done is match the back of the level to the square.
Allan from down under.
Allan from down under.
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Re: correct angle or measurement for front axle caster
Allan,
If you have a perfectly flat floor then that should work fine (flat not being the same as level!).
Out of interest; over the years I've tended to look for simple but accurate methods to do my alignments. The first one I did was nearly 40 years ago now (using a Dunlop optical gauge that I still have) and it fairly quickly became obvious how much a small anomaly in rim or base surface could affect the results.
Subsequently I've improved what I do, and some time ago I obtained an alignment hoist. However I found the most effective and simplest method for cars such as the T was to use the self-levelling cross-laser on the garage floor.
With this any anomalies in the floor, sagging springs and the like are able to be compensated for and, simply using my verniers from the laser line against the rim or kingpin bush, I can easily check camber as well as castor.
I mention this because these laser levels are relatively inexpensive now, and some people might be surprised just how much their floors are uneven or their springs sagging...
If you have a perfectly flat floor then that should work fine (flat not being the same as level!).
Out of interest; over the years I've tended to look for simple but accurate methods to do my alignments. The first one I did was nearly 40 years ago now (using a Dunlop optical gauge that I still have) and it fairly quickly became obvious how much a small anomaly in rim or base surface could affect the results.
Subsequently I've improved what I do, and some time ago I obtained an alignment hoist. However I found the most effective and simplest method for cars such as the T was to use the self-levelling cross-laser on the garage floor.
With this any anomalies in the floor, sagging springs and the like are able to be compensated for and, simply using my verniers from the laser line against the rim or kingpin bush, I can easily check camber as well as castor.
I mention this because these laser levels are relatively inexpensive now, and some people might be surprised just how much their floors are uneven or their springs sagging...
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- Location: 1807 East Ave. Hayward, CA 94541
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Re: correct angle or measurement for front axle caster
I'm probably going to get a lot of flack for this, but guy's.....it's a model T! Not a Bugatti or Rolls Royce. I'm not a finess mechanic. Even on the race car. I don't put a level on the floor. If it looks level to my eye, it's good. Close is good. Make sure everything is tight (not necessarily bushings and bearings), cotter pins or lock washers in place, you're good!
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Re: correct angle or measurement for front axle caster
I am going to agree with my friend yellow T racer on this one. The specification he gave is about twice the positive caster Ford called for on the model T. We have found this is perfect for light cars and especially for fast cars. And he’s right, model T’s don’t need laser alignment. A carpenter’s square on the floor is all you need.
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Re: correct angle or measurement for front axle caster
Ed, Erik,
You won't get a lot of disagreement from me, however in my case after a series of earthquakes the garage floor just isn't what it was so finding a reasonable spot to use a square isn't that easy.
As I use the laser for other cars it wasn't hard to use it on the T, and since I see no reason not to do as good a job as possible (and it makes it simple to do camber as well) it works well for me
Also in my case I needed to prove the alignment before being able to register my T for use on the road here so I felt it would help to do it 'accurately'. Trying to prove alignment using a square and string to youngsters with clipboards and tickboxes may not have worked very well, although in the end I struck some decent people who understood old cars so all was well
You won't get a lot of disagreement from me, however in my case after a series of earthquakes the garage floor just isn't what it was so finding a reasonable spot to use a square isn't that easy.
As I use the laser for other cars it wasn't hard to use it on the T, and since I see no reason not to do as good a job as possible (and it makes it simple to do camber as well) it works well for me
Also in my case I needed to prove the alignment before being able to register my T for use on the road here so I felt it would help to do it 'accurately'. Trying to prove alignment using a square and string to youngsters with clipboards and tickboxes may not have worked very well, although in the end I struck some decent people who understood old cars so all was well