Jerold's Rlaarlo Build

[Jerold]

Quick update

Hobby Town Colorado Springs
I was out of town last week and didn't get much done. Big shout out to Hobby Town in Colorado Springs! I always drop in when I'm in the area it's a real hobby store with real employees that don't mind helping with Frankenstein projects. Don't get me wrong, I love Norcal hobbies but it's a bit hectic to get any ones attentions sometimes and it's about 1/4 the size of the Hobby Town.

Hub Conversion Update
My super glue on the broken hub, looks to be solid which is a good sign. Polyethylene can be very difficult to glue and not knowing what type of plastic it is, I took a shot in the dark and got lucky. Just know that you can glue the parts.

While I was out of town was able to score some Traxxas 4-tec hubs (thanks HT). They about 2mm shorter than the Rlaarlo hub but fit just fine. I can add 2mm spacer to the top or bottom and adjust the ride height as well, or split the difference and add 1mm to both. I have spacers coming.

The steering links are within adjustment range and it looks like the steering arm clears the wheels. ... so far.

They drive shaft are still a bit of a mystery. I ordered the Traxxas drive shafts with CVDs. The factory front axle is 55mm. Scaling the Traxxas drive shaft picture it looks like they are ~40mm long, but the drive cups is about 1/2" longer too. So I "think" the axles will be pretty close and might work, but if not I can order some that are different lengths. HB racing, HPI and others have the lengths listed on the Amain website.

The bearings, shims and Traxxas 12mm hexes (see above) are also ordered.

The current list of parts to convert to Traxxas 4-tec hubs is below. It may change.

Top Plate
I really don't like the servo on floor were it is. After watching John linneman videos, he mounted the servo on the top brace. This is his car from the video.

That's a great idea and I'm going to work on that as well. The aluminum stock for the plate is ordered. The servo, receiver and antennas will be mounted there. @Dan B. Thanks for the link to antenna mount - also ordered.

I also have a new servo to replace the monster that's on there now. It's a low profile ProTek RC 140T Low Profile servo the 370T BL that I have now is just too much servo also the lower profile will save some room.

Taller Shocks
The end to end shock height is taller in the rear by about 1/4" (6mm). Which put less preload on the rear and makes it soft. Normally you want the back softer than the front to avoid becoming an oversteer machine. But we are going straight... hopefully.

My idea, we will see how this works, is to replace the rod ends with taller ones. I ordered the Traxxas TRA5525 rod ends. They look to be much longer than the stock one and we will see if they fit and if it helps the suspension.

This is roughly scaled and appear to be about twice a long. They are just plastic and can be shorted with a sander if I need to.

 

[Dan B.]

Quick update

Hobby Town Colorado Springs
I was out of town last week and didn't get much done. Big shout out to Hobby Town in Colorado Springs! I always drop in when I'm in the area it's a real hobby store with real employees that don't mind helping with Frankenstein projects. Don't get me wrong, I love Norcal hobbies but it's a bit hectic to get any ones attentions sometimes and it's about 1/4 the size of the Hobby Town.

Hub Conversion Update
My super glue on the broken hub, looks to be solid which is a good sign. Polyethylene can be very difficult to glue and not knowing what type of plastic it is, I took a shot in the dark and got lucky. Just know that you can glue the parts.

While I was out of town was able to score some Traxxas 4-tec hubs (thanks HT). They about 2mm shorter than the Rlaarlo hub but fit just fine. I can add 2mm spacer to the top or bottom and adjust the ride height as well, or split the difference and add 1mm to both. I have spacers coming.

The steering links are within adjustment range and it looks like the steering arm clears the wheels. ... so far.

They drive shaft are still a bit of a mystery. I ordered the Traxxas drive shafts with CVDs. The factory front axle is 55mm. Scaling the Traxxas drive shaft picture it looks like they are ~40mm long, but the drive cups is about 1/2" longer too. So I "think" the axles will be pretty close and might work, but if not I can order some that are different lengths. HB racing, HPI and others have the lengths listed on the Amain website.

The bearings, shims and Traxxas 12mm hexes (see above) are also ordered.

The current list of parts to convert to Traxxas 4-tec hubs is below. It may change.
View attachment 166569

Top Plate
I really don't like the servo on floor were it is. After watching John linneman videos, he mounted the servo on the top brace. This is his car from the video.
View attachment 166570

That's a great idea and I'm going to work on that as well. The aluminum stock for the plate is ordered. The servo, receiver and antennas will be mounted there. @Dan B. Thanks for the link to antenna mount - also ordered.

I also have a new servo to replace the monster that's on there now. It's a low profile ProTek RC 140T Low Profile servo the 370T BL that I have now is just too much servo also the lower profile will save some room.

Taller Shocks
The end to end shock height is taller in the rear by about 1/4" (6mm). Which put less preload on the rear and makes it soft. Normally you want the back softer than the front to avoid becoming an oversteer machine. But we are going straight... hopefully.

My idea, we will see how this works, is to replace the rod ends with taller ones. I ordered the Traxxas TRA5525 rod ends. They look to be much longer than the stock one and we will see if they fit and if it helps the suspension.

This is roughly scaled and appear to be about twice a long. They are just plastic and can be shorted with a sander if I need to.

View attachment 166571

Top shelf work, man. Very, very well done. This is one of my favorite builds ever to watch it all come together.

 

[Jerold]

Quick update on the Traxxas 4-tec hub conversion. It works... I think. I'm still missing a part but everything seems to align pretty well.

The axle is held in loosely by a single pin. They are right length axles but they didn't come the the pins or pivots. So I'm looking for those.

The Traxxas quality is so much better it will be a huge improvement if it all works and you can actually get Traxxas parts. I will let some else figure out the back.
The list of parts is below. I have not verified the pin/pivot bits yet. The Rlaarlo set is too big, and the Traxxas from the 4-tec kit is too small. Total cost is about $50. Some of this can be generic parts (bearings, spacers, washers) and save a few $$. You can probably reuse the Rlaarlo hexes too.

Description	Part Number	Price	Qty	Notes
Hot Racing M3 Medium Aluminum Standoff Spacer Set	HRASPC3005	$4.88	1
Traxxas 4-Tec 2.0 Steering Block	TRA8337	$4.00	1
Traxxas 4-Tec 2.0 Stub Axles	TRA8354	$12.00	2	Optional TRA8350X. Don't use the axles ($26.95)
Traxxas 5x11x4mm Ball Bearing	TRA5116	$3.50	1
Traxxas 5x8x0.5mm Teflon Washers	TRA1985	$2.00	1
Traxxas 12mm Hex Stub Axle Pin & Collar	TRA1654	$2.00	1
Traxxas 48mm Steel Constant-Velocity Driveshaft Bone	TRA7053	$7.00	2	Needs inner pin and pivot.
Traxxas Steel Driveshaft Rebuild Kit	TRA7055	$15.00	1	Not verified as the right set yet. Verified

 

[Dan B.]

Quick update on the Traxxas 4-tec hub conversion. It works... I think. I'm still missing a part but everything seems to align pretty well.

The axle is held in loosely by a single pin. They are right length axles but they didn't come the the pins or pivots. So I'm looking for those.

The Traxxas quality is so much better it will be a huge improvement if it all works and you can actually get Traxxas parts. I will let some else figure out the back.
The list of parts is below. I have not verified the pin/pivot bits yet. The Rlaarlo set is too big, and the Traxxas from the 4-tec kit is too small. Total cost is about $50. Some of this can be generic parts (bearings, spacers, washers) and save a few $$. You can probably reuse the Rlaarlo hexes too.

Description	Part Number	Price	Qty	Notes
Hot Racing M3 Medium Aluminum Standoff Spacer Set	HRASPC3005	$4.88	1
Traxxas 4-Tec 2.0 Steering Block	TRA8337	$4.00	1
Traxxas 4-Tec 2.0 Stub Axles	TRA8354	$12.00	2	Optional TRA8350X. Don't use the axles ($26.95)
Traxxas 5x11x4mm Ball Bearing	TRA5116	$3.50	1
Traxxas 5x8x0.5mm Teflon Washers	TRA1985	$2.00	1
Traxxas 12mm Hex Stub Axle Pin & Collar	TRA1654	$2.00	1
Traxxas 48mm Steel Constant-Velocity Driveshaft Bone	TRA7053	$7.00	2	Needs inner pin and pivot.
Traxxas Steel Driveshaft Rebuild Kit	TRA7055	$15.00	1	Not verified as the right set yet.

Well done, man. Very resourceful, and as you say, you can actually order and receive Traxxas parts in a couple days and not a couple months.
You should do a search on McMaster Carr for the pins and the pivots. Just measure what you need, you have a pretty good chance of finding them there.
My Rlaarlo parts order that I ordered on April 10 has still not shipped. Two months today, no shipment, no reply to emails, etc. The AK917 is a groovy little car, but Rlaarlo customer service is garbage.

 

[bozo]

Now that Amazon is selling it (under the Amoril brand) maybe we'll start seeing some parts available there also. You are doing some great work researching, analyzing and fitting substitute parts to work around the supply issue.

AK917 is a groovy little car, but Rlaarlo customer service is garbage.

You got that right! Mine is sitting on the shelf until we can get spare parts quickly. Hopefully the car/company doesn't die on the vine, they sure have ruined their reputation from the get go.

 

[Dan B.]

Now that Amazon is selling it (under the Amoril brand) maybe we'll start seeing some parts available there also. You are doing some great work researching, analyzing and fitting substitute parts to work around the supply issue.

You got that right! Mine is sitting on the shelf until we can get spare parts quickly. Hopefully the car/company doesn't die on the vine, they sure have ruined their reputation from the get go.

Mine won’t be run yet either. I got the roller, so I still have to install the electronics anyway. My first parts order included the upgraded motor mount, so I have to wait on that. For the life of me, I don’t know how anyone has the patience to set the gear mesh with the mount that was included.
The rest of the order was for shims, extra pills for the suspension pins (I hope to epoxy the existing holes and re-drill them for 0° rear toe) and a spare body that will be more accurately finished in the traditional Gulf livery.
I guess I should place another order that I can wait months to be delivered for consumables such as hubs, a-arms, etc.
Pretty frustrating. I think they may have bitten off a bit more than they could chew with the AK917. Their marketing was great, and all the big name Tubers got one and promoted them, and I think sales might have greatly exceeded their expectations. The parts chain is, I guess, still essentially nonexistent and will take awhile to come online.
I‘d feel sorry for anyone who bought one as their first RC, only to crash it and wait months for parts. That would be seriously demoralizing.

 

[Jerold]

Mine won’t be run yet either. I got the roller, so I still have to install the electronics anyway. My first parts order included the upgraded motor mount, so I have to wait on that. For the life of me, I don’t know how anyone has the patience to set the gear mesh with the mount that was included.

If you remove the rear cage and use a long driver you can get to it in the car. I'm using Wera hex drivers and they work.

The cage come out with like four screws.

Just get both screws in there barely snug, which is the hardest part. Becareful when you start the thread because it's not exactly a straight shot. Make sure you don't cross thread it. Then adjust the lash and snug it up.

I guess I should place another order that I can wait months to be delivered for consumables such as hubs, a-arms, etc.

The front and rear upper A-arms "look" like they might be interchangeable. Which means we could swap the front with the turn buckle from the rear and have better adjustment. Also the metal for the turn buckle looks to be crappy metal as everyone seems to break it. That will be getting replaced with some real metal.

 

[bozo]

spare body that will be more accurately finished in the traditional Gulf livery.

Fenix and Delta Plastik both offer 1/10 unpainted bodies. Not sure which one would be more accurate/fit on the Rlaarlo chassis.
Decals might be a problem.

 

[LibertyMKiii]

Fenix and Delta Plastik both offer 1/10 unpainted bodies. Not sure which one would be more accurate/fit on the Rlaarlo chassis.
Decals might be a problem.

As an FYI the Delta Plastiks Porsche 917 body is wider than this Rlaarlo car. The delta body is not a great fit for this car unless you are ok with a gap or wanting to use wider tires like the 45mm drag foams then it may be a good solution.

 

[Dan B.]

As an FYI the Delta Plastiks Porsche 917 body is wider than this Rlaarlo car. The delta body is not a great fit for this car unless you are ok with a gap or wanting to use wider tires like the 45mm drag foams then it may be a good solution.

Yeah, the 1/10 Delta bodies are mostly 200mm, the Rlaarlo is 190mm. The wheelbase is spot on at 260mm though.
Also @LibertyMKiii remember we‘re dealing with 1/10 Touring here and you can buy pretty much any wheel you can imagine in a wide range of offsets. I saw some BBS Motorsport wheels that would suit the 917 perfectly and they’re available from 3mm to 12mm offsets. I’m not sure what the offset is on the Rlaarlo wheels. But I’ll bet one could find their wheel of choice in the proper offset to bring them out that extra 5-6mm per side and also enjoy the stability of a slightly wider track.
I wish there was even a small percentage of options like that for the 100mm/17mm hex wheels.
I’m also obsessing over other body options as well. I’m really excited to have a wide range of really cool options for this scale. Like this bad boy…

 

[bozo]

Here's two other body options I've built up.
Both are using BSR Racing drag foams, fronts 32mm width 68mm diameter, rears are 45mm width 68mm diameter.
Only chassis mod is removing the 917 stuff from the rear, adding aftermarket body posts and cutting a new foam bumper.
If you want to use these wheels on the 917 body you have to cut the wheel wells larger and trim the bottom lip on the rear of the chassis wheel arch.
This is the Pro-Line '71 T/A

Here's an ebay $30 generic 1/10 body

 

[BarnFabRC]

Here's two other body options I've built up.
Both are using BSR Racing drag foams, fronts 32mm width 68mm diameter, rears are 45mm width 68mm diameter.
Only chassis mod is removing the 917 stuff from the rear, adding aftermarket body posts and cutting a new foam bumper.
If you want to use these wheels on the 917 body you have to cut the wheel wells larger and trim the bottom lip on the rear of the chassis wheel arch.
This is the Pro-Line '71 T/A
View attachment 167316

Here's an ebay $30 generic 1/10 body
View attachment 167317

That Trans-Am is RAD! What chassis is it on?

 

[bozo]

What chassis is it on?

Both bodies are on the same AK917 chassis.

 

[Dan B.]

Both bodies are on the same AK917 chassis.

Yeah man, 1/10 Touring opens up a whole, beautiful realm of possibilities. That ‘71 T/A is the cats a$$!

 

[Greywolf74]

That T/A body is freakin amazing!!!

 

[Jerold]

Quick Update

No Brakes
I figured out that my brakes didn't work and it would just full throttle reverse on me.

You can see this in the First Drive Video, right at the beginning. At the time I didn't realize what it was doing and figured it was just a giant motor with tiny car.

The setup is an MMXS 8S with a TP Power 3460 motor. The motor is unsensored and when I put it together it turned the wrong way. So I swapped two wires which corrected the direction. However, it turns out that I need to reverse my transmitter and let the motor do what it does.

Thinking about this now this is what caused me to crash into the curb. Like duh. I'm not sure why I didn't figure this out earlier, probably just not paying attention to the behavior. It's all a work in progress.

Traxxas Hub Conversion
It works! However, my spare parts (and finally the sliding motor mount) showed up from China. Glad they are here, but I don't actually need them now. I will see how the Traxxas Hubs play out. If they seem to be an issue I have the Rlaarlo parts as a backup. This is only on the front, but I'm sure there is a similar solution for the rear.

There is still one part that I probably need to upgrade, which is the toe links. They are extended pretty far out now and I have concerns with the cheap metal they use. I might drop by the hobby store to see what they have for turnbuckles. Then I can replace the rear ones too.

Description	Part Number	Price	Qty	Notes
Hot Racing M3 Medium Aluminum Standoff Spacer Set	HRASPC3005	$4.88​	1​	Notes
Traxxas 4-Tec 2.0 Steering Block	TRA8337	$4.00​	1​
Traxxas 4-Tec 2.0 Stub Axles	TRA8354	$12.00​	2​	Optional TRA8350X. Don't use the axles ($26.95)
Traxxas 5x11x4mm Ball Bearing	TRA5116	$3.50​	1​
Traxxas 5x8x0.5mm Teflon Washers	TRA1985	$2.00​	1​
Traxxas 12mm Hex Stub Axle Pin & Collar	TRA1654	$2.00​	1​
Traxxas 48mm Steel Constant-Velocity Driveshaft Bone	TRA7053	$7.00​	2​	Needs inner pin and pivot.
Traxxas Steel Driveshaft Rebuild Kit	TRA7055	$15.00​	1​

Suspension Adjustment
When I run the car it happily wanders all over the road like a lost puppy. I trimmed the steering, then sub trimmed it but it still wanders. After going over the suspension again, I noticed that right side A-arm camber was adjusted differently than the left. It looks straight when I set it up but also noticed that the aluminum (which I don't have) arms have numbers on them that refer to the camber setting. Clearly I did this wrong. They are the same now.

Eventually I want to try the rear arms in the front and if that works, I will have a more grainular camber adjustment.

The other bit of wonkiness is the is the toe. With the Traxxas hubs the steering arms are set farther apart. I adjusted it but it still had a bit of toe-out, which is bad for stability. I adjusted it a bit more to have to some toe-in and it's seems to be a little better.

I need to go through the suspension setup again and double check everything anyway.

However...it's super squirrely on the throttle.

Electronic Settings
I turned up the throttle speed to like 30. So it takes a while for it to ramp to full power. Also I turned the punch control so 50%. Both of these should "help" me from binning it when I get throttle happy.

After all the motor setup, ESC and TX adjustments, I did a little test on the bench and see the throttle curve, current, voltage, etc all seem to align in the data log and I have more reasonable RPM for the power out.

Maybe this weekend I will get some time to go crash it... I mean test it.

The contest has a qualification of 80 MPH by end of June and the clock it ticking. So I need to make something happen if I'm going to be in it. In the end I seriously doubt I can compete with the big boys but if I can get 120mph from it I'd be happy.

Many of those big boys have also helped me a lot with various things and it's greatly appreciated!

 

[Bogda89]

Quick Update

No Brakes
I figured out that my brakes didn't work and it would just full throttle reverse on me.

You can see this in the First Drive Video, right at the beginning. At the time I didn't realize what it was doing and figured it was just a giant motor with tiny car.

The setup is an MMXS 8S with a TP Power 3460 motor. The motor is unsensored and when I put it together it turned the wrong way. So I swapped two wires which corrected the direction. However, it turns out that I need to reverse my transmitter and let the motor do what it does.

Thinking about this now this is what caused me to crash into the curb. Like duh. I'm not sure why I didn't figure this out earlier, probably just not paying attention to the behavior. It's all a work in progress.

Traxxas Hub Conversion
It works! However, my spare parts (and finally the sliding motor mount) showed up from China. Glad they are here, but I don't actually need them now. I will see how the Traxxas Hubs play out. If they seem to be an issue I have the Rlaarlo parts as a backup. This is only on the front, but I'm sure there is a similar solution for the rear.

There is still one part that I probably need to upgrade, which is the toe links. They are extended pretty far out now and I have concerns with the cheap metal they use. I might drop by the hobby store to see what they have for turnbuckles. Then I can replace the rear ones too.

Description	Part Number	Price	Qty	Notes
Hot Racing M3 Medium Aluminum Standoff Spacer Set	HRASPC3005	$4.88​	1​	Notes
Traxxas 4-Tec 2.0 Steering Block	TRA8337	$4.00​	1​
Traxxas 4-Tec 2.0 Stub Axles	TRA8354	$12.00​	2​	Optional TRA8350X. Don't use the axles ($26.95)
Traxxas 5x11x4mm Ball Bearing	TRA5116	$3.50​	1​
Traxxas 5x8x0.5mm Teflon Washers	TRA1985	$2.00​	1​
Traxxas 12mm Hex Stub Axle Pin & Collar	TRA1654	$2.00​	1​
Traxxas 48mm Steel Constant-Velocity Driveshaft Bone	TRA7053	$7.00​	2​	Needs inner pin and pivot.
Traxxas Steel Driveshaft Rebuild Kit	TRA7055	$15.00​	1​

Suspension Adjustment
When I run the car it happily wanders all over the road like a lost puppy. I trimmed the steering, then sub trimmed it but it still wanders. After going over the suspension again, I noticed that right side A-arm camber was adjusted differently than the left. It looks straight when I set it up but also noticed that the aluminum (which I don't have) arms have numbers on them that refer to the camber setting. Clearly I did this wrong. They are the same now.

Eventually I want to try the rear arms in the front and if that works, I will have a more grainular camber adjustment.
View attachment 167738


The other bit of wonkiness is the is the toe. With the Traxxas hubs the steering arms are set farther apart. I adjusted it but it still had a bit of toe-out, which is bad for stability. I adjusted it a bit more to have to some toe-in and it's seems to be a little better.

I need to go through the suspension setup again and double check everything anyway.

However...it's super squirrely on the throttle.

Electronic Settings
I turned up the throttle speed to like 30. So it takes a while for it to ramp to full power. Also I turned the punch control so 50%. Both of these should "help" me from binning it when I get throttle happy.

After all the motor setup, ESC and TX adjustments, I did a little test on the bench and see the throttle curve, current, voltage, etc all seem to align in the data log and I have more reasonable RPM for the power out.

Maybe this weekend I will get some time to go crash it... I mean test it.

The contest has a qualification of 80 MPH by end of June and the clock it ticking. So I need to make something happen if I'm going to be in it. In the end I seriously doubt I can compete with the big boys but if I can get 120mph from it I'd be happy.

Many of those big boys have also helped me a lot with various things and it's greatly appreciated!

Who is so far leading when it comes to top speed achieved?

 

[Jerold]

As far as I know John Linneman is leading at 162 mph. But this is still the quals and others (VW TurboWolf and Raz Shrifrin) are on the 150's. So it should be a good race. I think John is showing his hand too much. I would sit on the lowest number to get by and post the big the big ones at the last hour.

 

[Jerold]

Motor Mount
The sliding mount was installed. It fits on the chassis just fine. However, the hardware is questionable.

Maybe I missed something? The four, not sure why there are four?, screws for the slider and they are too short. They grab about 2 or 3 threads and will strip easily. If you use this mount just plan on getting some longer screws. Also I'm not sure why there is a grub screw in there? I have one that comes with my pinion and I'm sure it's better quality.

Also the plastic cover doesn't fit anymore. If you want to run it plan to cut it up. Personally, I kept it to add a layer between my battery and the buzz saw.

Team Corrally Tires
What seems to happen is under power, going 20 mph or so, the car just breaks traction and spins out. It's all over the road and uncontrollable for the most part. The Gryo is on, and now with the correct orientation, but it's not helping much. I keep it at about 5% anything more and I get a wobbly oscillation.

My roads are pretty smooth and I "might be" over sprung? It looks fine, not bouncy or anything, but I can't get going fast enough to really utilize the springs. But I really don't think the springs are the issue at the moment. However, I might pull my inner springs and see if it's better.

The real problem seems to be the foams. When I ordered my BSRs from Island Hobby, they sent me Team Corrally Tires. Same size, same hardness; I'm assuming the BSR were out of stock. I duuno? What I do know is they are part of my handling problem. They have almost no traction when compared to the factory rubber tires. I stuck the stock tires back on and it was much better. So the TC tires are off the car.

Gears
The stock 48P spur gears aren't strong enough and seem to get trashed pretty quickly. It's most likely due to the metal used on the factory spur gear, because the Robinson Racing Pinion is 100% OK. You can see the metal flakes and mushing happening here. This actually locked up on me.

It's time to look at upgrading to Mod 1. The pitch (48P or Mod 1) is the ratio of the number of teeth to the diameter of the gear. In the case of 48P it's an inches and Mod 1 is metric and they are not the same. So we have to some math.

Gears are actually very complex. There are a lot of dimensions and terms, it's all very confusing. However we are not designing the gears and we only need a few critical measurements, the number of teeth, Center Distance and the Pitch Circle. We also need the Outside Diameter to make sure we clear the chassis.

How do we know what will fit into the Rlaarlo factory mount? There is another metric for the system called Total Tooth Count, meaning if I add up the number of teeth on the pinion and the spur, that is the total number of teeth and it defines the Center Distance measurement. If we use a 30T pinion and a 60T spur, we have 90 TTC.

Looking at the Rlaarlo book with the gearing chart (which I can't seem to find at the moment) the min/max TTC is 97 and 123. Meaning that I need at least 97 tooth count and no more than 123 tooth count @ 48P. Now using some fancy math, that is conveniently done for me (https://evolventdesign.com/pages/blank-calc), I can get the Pitch Diameter of each gear then add them together to get the Center Distance. The Pitch Diameter is the circle that contacts the other gear.

Other than that you need to make sure they don't rub on the chassis. I'm running a 36mm motor that is flush with the chassis, so I need my max Outside Diameter for the pinion is <36mm. The largest spur gear from Rlaarlo is 78T or 42.33mm Outside Diameter, so less than 42mm.

To calculate the Center Distance on the existing 48P gears, I can assume one of the gears is 50T @48P it makes the it easy to vary the other one and use 47T and 73T to get my min/max values. A combination of 50T+47T=97T and 50T+73T=123T. Using the calculator, this means I need a Center distance of ~52-65mm

Luckily metric is always easier. Converting from 48P to Mod 1 is easy if we know the Pitch Diameter, because it is the same as the number of teeth on a Mod 1 gear in mm.

Also convenient with Mod 1 gears, the Outside Diameter is the tooth count +2. So the max pinion gear size we can use is 33T @ Mod 1. And the max spur is 40T.

We also know the TTC is the same as the Center Distance.

Which means for Mod 1

• TTC for a Mod 1 needs to be between 52 and 65
• Pinion max tooth count of 34T
• Spur max tooth count is 40T

Assuming all my math is correct, which is a big "IF" I have a spreadsheet tool (attached) to help with all this. Just change the Cells B12 & B13 to the values you want and it will tell if it will work.

It checks the min/max TTC, the maximum Outside Diameter of the Pinion & Spur and gives you the gear ratio.

 

[Dan B.]

TMI on the mod-1 explanation. Enough to scare anybody away from doing the swap!
But seriously man, great information.
Just curious, what 48p spurs will go in there, I mean by brand/type, not size? I’m sure your RR pinion is so much better than the Rlaarlo ones it’s crazy, was wondering if a quality 48p spur was available from RR, Tekno, Saga, etc.