Is 12+ mph vibration normal? (Low gear)

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Model T Ford Forum: Forum 2016: Is 12+ mph vibration normal? (Low gear)
Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Monday, August 01, 2016 - 04:17 pm:

So, I've adjusted by rod caps and I no longer hear the slight knock I had heard before during 30 mph deceleration in high gear.

However, I had wondered if adjusting the rods would eliminate the 11 mph low gear vibration. It reduced it, so I have now taken her up to about 16 mph In low gear, but there is still a vibration that begins around 12 mph.

By the way, what is the maximum safe speed in low?

Yesterday I read up on flat plane crankshaft design and learn more about the inherent vibration it causes. This is the first model T I've ever written in, so I don't know if I'm being overly cautious or not.

Thank You in advance. The main bearings seemed OK to me. The car does not even leak oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Monday, August 01, 2016 - 04:46 pm:

Many things can cause vibrations. You would also have a vibration in high gear about 30 mph.

Assuming that the compression is even on all cylinders and that the wheels are straight and in balance, spark is good on all cylinders and the fuel mixture is at the "sweet spot":

The vibrations are most likely in the engine and transmission. There are many parts to be balanced and any of them out of balance could cause vibrations. All pistons should weigh the same. The small ends of the rods should weigh the same, the large ends of the rods should weigh the same. The crankshaft itself should be in balance, the flywheel in balance, the magnets in balance. The triple gears should all weigh the same amount. There might be other things to balance as well.

Actually the balance is not critical unless it is severe or you are using the car as a speedster where you will need to run at high speeds all the time.

You normally drive only short distances in low unless you have very steep hills to climb and in high you can adjust your speed to run with the least vibration. Usually the vibration will be at a certain speed and either going slower or faster will stop the vibrations.

I would suggest that you find someone familiar with Model T's in your area and let them ride in your T and likewise you ride in their T to determine whether your vibration is excessive. Have a lot of fun driving your car.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Monday, August 01, 2016 - 05:09 pm:

Thank You, Norm.

The nearest member so far is 3 hours away by trailer.

High gear runs great as fast as I want to drive without brakes. 40ish mph is no problem and is as smooth as my wheels are round.

Compression is good and no oil is being burnt. The rods look mismatched, so I may go ahead and replace them and go with lighter pistons. That will be a good chance to balance them all.

That #4 rod is a bugger and I'm hoping the #4 piston can clear the firewall without pulling the engine. I will search for a thread on that topic.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dale Peterson College Place, WA on Monday, August 01, 2016 - 05:27 pm:

What year Model T's did you end up with? In my 16's the only problems with clearance has been the rear most head bolts when torquing them and the rear most valve when doing a valve seat grinding engine in place. I did a piston set replacement after #2 seized without problem. Hardest part was removing the rod cap on #4.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Monday, August 01, 2016 - 06:30 pm:

1924


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Hatch on Monday, August 01, 2016 - 07:22 pm:

Chris: I am in B'ham. I plan to go to Ardmore swap meet next Sat. I should be easy to find, I bet I am only one there with T parts. Dan


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Monday, August 01, 2016 - 07:26 pm:

Thx Dan

Unfortunately I'm driving a wedding event in Chattanooga Saturday.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Monday, August 01, 2016 - 07:36 pm:

Chris, you keep referring to a speed of 12 mph in low gear being a shift point to go into hi gear. I'm curious to know where the 12 mph comes from.

When I drive any of my Model T's I shift when the engine sounds right and the car is rolling at a significant speed to continue on down the road without causing excessive lugging on the engine or over-revving on the shift. I guess all the years of driving truck tuned me in as to when to shift.

Anyway, I'm curious, why 12 mph?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Monday, August 01, 2016 - 08:24 pm:

I'm using a gps for a speedometer


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan Treace, North FL on Monday, August 01, 2016 - 08:33 pm:

Here is a nice chart from Dyke's Manual, shows the speed range in gearing.

Normally, low speed is engaged to just get under way, and when climbing steep hills, mostly for me low speed up a steep hill is max. of 8-10mph or the engine is really wringing out, and the trans is really growling and sounds like it will vibrate apart :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Garrison - Rice Minnesota on Monday, August 01, 2016 - 11:55 pm:

That's an interesting chart. Now I'm a bit curious and wondering what speed and RPM I shift at.I don't figure I'm going to worry about it too much. In five years I don't think I've done a lot of damage by just driving the car the way I do. But the chart is interesting. I'd be willing to bet Grandpa didn't have a tach or speedometer in his Model T. Unless maybe he was doing a lot of street racing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Tuesday, August 02, 2016 - 04:07 am:

Omg! Thank You! This is exactly the info I needed.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Tuesday, August 02, 2016 - 04:10 am:

In my area almost every inch of roadway has an incline or decline. No wonder I'm the only T member for miles around.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Tuesday, August 02, 2016 - 01:56 pm:

Chris,

Just about any T will vibrate at some given engine speed. I think you're winding the motor out a bit much. I up-shift probably at about 5 - 10 mph. If you're used to driving a "modern" manual transmission car, the tendency is to wind-out the gears. You don't need to, and shouldn't, do that in a Model T. They should be perfectly capable of going into high at 5 mph and accelerating from there. The only exceptions are when you need to scoot out into traffic kind of quickly.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Tuesday, August 02, 2016 - 02:29 pm:

Thank You Jerry


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Tuesday, August 02, 2016 - 03:06 pm:

I've never paid a lot of attention to the exact speed when shifting, just doing it when the engine "sounds right". So when I went to town today I kept an eye on the speedometer to see how fast that is. It turned out to be 8 to 10 mph. I suppose if I were starting up a fairly steep hill, I'd wind it up a bit higher. Maybe 12 or 13 mph.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Tuesday, August 02, 2016 - 04:29 pm:

Thank You Steve


Top of pagePrevious messageNext messageBottom of page Link to this message  By Greg Adkisson on Tuesday, August 02, 2016 - 07:24 pm:

The speedometer app for your smart phone really is accurate...what I use in my 15 roadster


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dennis Plank - Three Way, TN on Tuesday, August 02, 2016 - 07:38 pm:

You might actually be winding it tighter than you think if you are depending on your phone's gps app. Most of those apps do not update fast enough to keep up with your speed accurately when you are starting out. In other words, if you are seeing 12 mph on your phone, you might be hitting 15 to 16. I shift by ear. You don't want to lug your engine hard when you shift to high, nor do you want to wind it out tight.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Tuesday, August 02, 2016 - 08:04 pm:

I'm thinking going 12 MPH in low is nearly self destruct mode........YIKES


Top of pagePrevious messageNext messageBottom of page Link to this message  By Corey Walker, Brownsboro TX on Tuesday, August 02, 2016 - 10:23 pm:

I'm glad I read about a speedometer app for a smart phone. I never knew about it. I'll see when I shift mine tomorrow and see what speed I run usually. I wish it wasn't dark but my headlights don't work.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Steve Jelf, Parkerfield KS on Wednesday, August 03, 2016 - 02:37 am:

I should have mentioned that I'm using a bike speedometer. I'm not sure that it's accurate at low speeds (under 15 mph).


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Wednesday, August 03, 2016 - 10:16 am:

Steve,

If it's designed right, a bike speedo should be the most accurate at those speeds, since most bikers don't get much above that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Laughary on Wednesday, August 03, 2016 - 12:24 pm:

Steve, is the bike speedometer mechanical or GPS based? I have too much glare on my phones and GPS tablet.

Using the "Night Mode" display helps, but I am searching for a better solution.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jerry VanOoteghem - SE Michigan on Wednesday, August 03, 2016 - 03:43 pm:

Chris,

They are usually neither. On a bicycle, there is a pick-up unit that mounts on the front fork and a magnet(?) that clamps to a spoke. The p.u. counts passes of the magnet and calculates speed based on the wheel size you've got, (which you input into the unit).

On a Model T, there are several ways to mount the p.u. & magnet. Maybe someone can provide photos of theirs.

BTW, I realize you asked Steve, sorry if I butted in...


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Schreiber- Santa Isabel Ecuador on Wednesday, August 03, 2016 - 03:48 pm:

Some info and pics here:
http://www.mtfca.com/discus/messages/257047/285228.html


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