Model 20 diff pinion problem

[Guest Tom Bastian]

Hi all Model 20 friends.

I recently bought 1910 Model 20 SN 2336. Its in fairly good running condition, but needs a little cosmetically. It didn't run very well at first, but once I changed the timing to 20 deg BTDC instead of the 30 deg ATDC it came with, it ran a lot better. I have been driving it up and down our long driveway while I wait for a title issue to resolve, and last weekend lost all drive. It turns out the pinion on the end of the drive shaft rotates relative to the shaft, which is obviously not good. Pictures show the pinion.

Question- What holds the pinion to the end of the drive shaft, and what is supposed to keep it from rotating? It appears to have a keyway on the pinion ID, but I can find no equivalent keyway on the mating OD of the shaft. I also do not know how to remove the pinion from the end of the drive shaft. Do I have to take the universal joint off the front of the shaft and withdraw the assembly out the back of the tube?

Another curiosity-

The tube is labelled as 4 1/2:1, but the runabout should have come with a 4:1 diff. Also, the pinion only has 10 teeth, which tells me it is a 4.8:1 rear end. Maybe this is why I can't get over 28 mph (GPS).

I am also interested in the floorboards on this car. It looks like an aluminum sheathing over wood. Is this original or a product of the 1950s restoration?

Any thoughts or hints are welcome

Tom Bastian

[trimacar]

Hi- nice car...someone has modified your driveshaft. The original driveshaft and pinion was made all in one piece, that is, no separate gear and shaft. Apparently whatever method the person used of holding them together on your modified set has failed.It also appears to have been converted to tapered roller bearings, this is usually done at the top end too, thus making the driveshaft the equivalent of the spindle, with the driveshaft housing being the "wheel". The original bearings were different.

The original driveshaft was inserted into the housing from the rear, and the universal joint pinned to it on the opposite end. You remove a two pipe plugs on the upper end of the driveshaft housing, and drive a tapered pin out of the universal joint, thus releasing the driveshaft itself.

There is a gentleman making new driveshafts and gears, I don't have his name at hand but could find it.

[Guest Tom Bastian]

Thanks David,

The tapered pin came out OK and released the drive shaft and tapered roller bearing out the back. It did not shed any more light on how the pinion was originally attached however. It appears that there is a slight shoulder on the aft surface that is keeping the pinion on the shaft.Its possible this was once a small weld bead, but its hard to tell, as the aft surface has been ground flat. What do you think about welding again? I worry about affecting the pinion hardness.

I am interested in changing the ratio eventually, preferably to a 3.5:1, but will probably just try to make the current set-up work for now. I would be interested in the name of the gear guy.

Tom Bastian

[1910Hupp]

Nice car Tom

Can't help you on the rear end as I've never had mine apart and I suspect Mine has been modified as well.

With regards to timing if you follow the factory handbook way of timing the engine then you line up TDC on the flywheel with a mark on the front of the block

This mark is slightly to the right of a mark which marks TDC ie The correct timing is slightly retarded - All the best Karl

[nickelroadster]

If nothing else you should be able to have a key way cut in your drive shaft and just use a square key to hold it. Now you need to find out how the pinion is held to the drive shaft. Can you rotate it by hand as it sits?

[Guest Tom Bastian]

The pinion rotates by hand, but is held captive on the end of the shaft by a small lip of material on the end of the shaft. I beliee this lip is what is left of a weld bead. When I lost drive, I tried both high gear and reverse with no effect, so I'm sure that 'machined the contacting surfaces smooth, to allow the current pinion rotation. My problem with machining a keyway is that I have to remove the lip to remove the pinion. Then there is nothing left to hold the pinion axially in place. MIG welding looks like the best option to me at this point. Trying to minimize heat into the components and keep it local to the lip and pinion end surface. After all, we are only talking about 20 HP here. If I can be gentile with the clutch and not dump a bunch of torque from the flywheel... It has apparently lasted the last 50 years, according to the daughter of the previous owner/restorer.

No one has commented on the floorboard question. Any clues on the original material?

[trimacar]

The fellow making gear sets is Hugh Montgomery, jmontgomerynospam@odyssey.o.ca (remove nospam)....

Since the original was all one piece, gear and shaft, welding the gear to the shaft does essentially the same thing. Be gentle with the heat, go slow, as you mention.

I don't know the answer to the floor board question. I've seen everything from diamond plate like yours, linoleum, and a while back there was a fellow who replicated a rubber floor mat with the Hupmobile name in script on it, wish I had one of those, supposedly copied from an original mat....

[1910Hupp]

The fellow making gear sets is Hugh Montgomery, jmontgomerynospam@odyssey.o.ca (remove nospam)....

don't know the answer to the floor board question. I've seen everything from diamond plate like yours, linoleum, and a while back there was a fellow who replicated a rubber floor mat with the Hupmobile name in script on it, wish I had one of those, supposedly copied from an original mat....

I made a a mat with the embossed Hupmobile logo in it . Was surprisingly easy to do . Made the mold by water jet cutting three peices of scrap metal and laminating them together Cast the logo in Devcon rubber and bonded it to the mat turned out pretty good . I can post a picture if you would like David . Regards Karl

[trimacar]

Yes please, do you have pictures of the process you went through? I seem to remember an article about this mat

[Guest Tom Bastian]

Karl-

Regarding timing, I was going by Harold Sharon's book 'Understanding your Brass Car". In it, he says the manufacturers originally recommended TDC because the octane of the fuel was so low that early timing risked detonation. With today's 86 octane and the 4:1 compression ratio, there is no risk of that. Given the spread-out intake charge geometry, he advocates substantial advance. With the Model 20's fixed magneto timing, this will always be a compromise between starting and running, so I've gone as far advanced as possible without strong starting crank kick-back. I have purchased a 'parts' Bosch magneto with adjustable timing and salvaged the adjustable points cover assembly from it. I intend to hook this up to the hand throttle such that advancing the hand throttle retards the timing. That way I can retard for start, then advance to a better running position.

Tom Bastian

[1910Hupp]

Tom

In the owners manual it tells you how to set up the timing Essentially there are two marks on the front of the forward cylinder block . Looking from the front of the car the left mark is TDC and the mark 3/8ths to the right of this is the one you line up the TDC mark on the flywheel with . You then set up the magneto so that the points are about to open when the rotor is on the segment for Number one spark plug then mesh the cam and magneto gears. Of course that is for the original fixed magneto . What confused me for a long time is I read a report on the Hupmobile which stated that "although the timing was fixed Robert Hupp stole an idea form the French and set the timing slightly advanced" - well of course following the factory instructions actually the ignition is set slightly retarded !. I to have modified the magneto to provide variable timing for mine. I have set the magneto retarded on the original timing mark ( ie slightly retarded from TDC) whch seems to work fine for me although I must admit I don't fiddle with the ignition timimg as much as I though I would when driving. If you need a copy of the owners manual I'm sure one of us will send you a scan of it -Karl

[Guest Tom Bastian]

Thanks Karl-

I raided the Hupmobile club library and got copies of the Model 20 1910 Instruction Book, the 1910 catalog and the Model 20 Service Parts list. I also bought a back-issue of the Horseless Carriage Gazette from Nov-Dec 1971 which has a very detailed article by Bill Cuthbert on the various detail changes throughout Model 20 to aid in dating.

Is the owner's manual you talked about the same as the club's Instruction Book?

Tom Bastian

[Guest Tom Bastian]

David, Karl and Nickelroadster. Thanks for all the help and comments. I will contact Hugh Montgomery regarding a new shaft and gears. I did check the ring gear and it has 48 teeth, so it is definitely geared low.

For now, I will work on welding the pinion back on the current shaft after I return from Long Beach. I am a corner worker and never miss the Indycar (and CART and F1 and F-5000) race each year.

The floormat, (continued on a separate thread now) looks great and I will have to customize my home-made rubber floormat now.

BTW, I have made a PDF of the Model 20 'dating' article if anyone is interested.

Tom Bastian

[1910Hupp]

Hi Tom

I suspect you have the correct book

I have recieved a PM suggesting I check that the instructions I gave you for timing are correct . Like me the messenger can't work out why a fixed magneto would be set retarded! If you look on the post " '10 Hup drive train repairs " (sorry don't now how to link it) the Owners Manual instructions are reproduced by Edgar Bowen (who I think probably knows as much about early Hups as anyone alive) . He (and the Hupp owners book) definitely states rotate the fly wheel 3/8ths of an inch to the right from the TDC (first) mark to set the magneto - That must be retarding (although not much) the ignition. ?? I guess its all academic because the ignition setting that starts the car and allows it to run well is the correct setting. Karl

[Tom400CFI]

The fellow making gear sets is Hugh Montgomery, jmontgomerynospam@odyssey.o.ca (remove nospam)....

I'm going through a similar thing and had a new R&P made by a company called LAWLER GEAR. They did a good job and I'm in the assembly process right now, trying to set up pinion depth. Lawler Gear's method for attaching the pinion gear to the shaft was splines, which I think is a decent way of doing it.

EDIT: After trying to install and set up my gears, it was immediately apparent that my ring gear was warped. I called Lawler Gear and talked to them about it quite a bit. It was a good conversation, but they didn't offer much help. They did take the gear back, machine the face, and suggested I used shim stock to make the gear run true. The problem is that they heat treat the gear, and it warps. They contend that there is no way to avoid it. I wonder if they heat treated the blank, THEN cut the teeth? I don't know, but I now have a warped ring gear in my Hupp, so my previously favorable recommendation for Lawler Gear is retracted. If I were doing it again, I'd shop around more and ask about how one would handle the heat treating process.

Edited October 1, 2013 by Tom400CFI (see edit history)

[Guest Edgar Bowen]

Re magneto timing and a trap for the unwary. I followed the handbook directions to a T and then found someone had actually altered the timing of the magneto itself. So before doing anything check that the magneto points are opening when they are suppose to. Make sure that is right first. I use a fixed spark DU4 and am very happy with it.

At first my engine was under performing until I widened the tappet points to 18 thou and 20 thou with brass instead of wood tappet inserts.

As far as dif. ratios go, three ratios were used on runabouts. 3.5 : 1 ; 4 : 1; then 4.5 :1. The latter is the most common. They started with the high ratio until it was found too fast for the road conditions and hill climbing, and in the end they opted for the low ration. I fitted a T Ford dif. inside the Hupp axle housing with 3.5 : 1 ratio and it gives a 'thrilling' performance with max speed of 50 MPH (80 Kph) and comfortable cruising at 60 Kph.

[Guest Tom Bastian]

It finally cooled off here in Tucson and I got back on the Model 20 drive shaft fix. Here are pictures of the pinion weld my son did-

I took it out Saturday morning to see if it would hold up, and so far, so good. Went about 10 miles in total. Up and down some hills and shifted up and down several times with no drive train issues.

This is the most driving I have done with the Hupp so far. I notice when I get up around 30 mph, the steering gets very unstable. I believe the problem is toe-out at the front. It darts a lot and needs constant attention to keep it in one lane. The first solution is to keep it under 30 and its much more managable. A longer term solution is to try to dial in a little toe-in. I see no adjustability. Has anyone tried changing the steering alignment geometry?

Tom

[Tom400CFI]

I would set the toe to zero (no toe in or out) and then use wedges between the spring and axle to get more caster.

[Guest Tom Bastian]

I may be missing it, but I see no length adjustment on the tie-rod between the two front steering arms. Where is the toe set?

Tom

[Guest Edgar Bowen]

I may be missing it, but I see no length adjustment on the tie-rod between the two front steering arms. Where is the toe set?

Tom

No Tom, there is no adjustment. It may be irregular if not illegal but I adjusted my toe-in by heating up and bending the steering knuckle to get the required toe-in. I don't remember how much it was now but I agree if you want to drive over 30MPH it is advisable. The caster angle needs to be 3 degrees like a T Ford.

I find the way to handle the steering is with elbows firmly tucked into your side, hang onto the wheel firmly and just lean over to the left or to right. They are a nightmare to drive on rough roads.

Edgar

Edited October 1, 2013 by Edgar Bowen (see edit history)

[Guest Tom Bastian]

I decided to check for loosness in the suspension joints, and found most of my steering problem. All 24 bolts on the whel hubs were loose to varying degrees. I was getting rear steer from the wheels flexing laterally. I tightened the hubs and it is much more stable. Set a record of 35.8 mph (downhill) on my morning 15 mile drive. Lots of waves, and one family flagged me down for a photo session.

Tom

[Guest Edgar Bowen]

I decided to check for loosness in the suspension joints, and found most of my steering problem. All 24 bolts on the whel hubs were loose to varying degrees. I was getting rear steer from the wheels flexing laterally. I tightened the hubs and it is much more stable. Set a record of 35.8 mph (downhill) on my morning 15 mile drive. Lots of waves, and one family flagged me down for a photo session.

Tom

Hi Tom, I'm glad to hear you have improved the steering by tightening the wheel bolts. You may find you even have to tighten the fit of the spokes sometime. There are two ways to do that, a strip of say 20 guage steel between the wooden felloe and rim, or shims of hard wood between the spoke wedges. Either way requires removal and re-fitting of the steel rim which means heating to expand it. It is not something one wants to do but is effective.

Giving spectators the pleasure of watching our Hupps go by is one of the rewards of driving them.

Edgar